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Question 1

endemic

Answer 1

Disease is constantly present in a population usu. at low frequency

Question 2

epidemic

Answer 2

Disease suddenly increases in a population

Question 3

pandemic

Answer 3

Disease increases within large widespread populations usu. worldwide

Question 4

MORTALITY

Answer 4

MORTALITY
Leading infectious killers
– acute respiratory infections: pneumonia, influenza
+ HIV AIDS, diarrhoeal diseases, TB, malaria, measles

Question 5

MORBIDITY

Answer 5

MORBIDITY
Infections = huge burden
(measured as disability adjusted life years; DALYs)
= so sick -> cannot contribute to the community • cannot work
• cannot care for children

Question 6

major factors contibuting to the emergence of infectious disease

Answer 6

1. human demographics and behavior
2. technology and industry
3. economic development and land use
4. international travel and commerce
5. microbial adaptation and change
6. breakdown of public health measures

Question 7

aim of active immunisation

Answer 7

Aims
• to produce long lasting immunity to pathogens in individuals and the community
• to eliminate the pathogen (where possible)

Question 8

symbiosis

Answer 8

= Living together of organisms

Question 9

Commensalism:

Answer 9

Commensalism: ‘commensal’ = lives in / on another
ie Interaction between normal flora and host  One partner benefits
 Other partner not affected

Question 10

Mutualism

Answer 10

Mutualism: ‘mutualist’ / ‘symbiont’ ->Both partners benefit

Often obligatory eg ruminants, GIT flora

Question 11

Parasitism

Answer 11

Parasitism: ‘parasitic organisms’
Pathogen = parasitic organism causing specific disease
- One partner benefits
- Other harmed

Question 12

Benefits: of normal flora

Answer 12

Benefits:
• Compete with pathogens for attachment sites, nutrients
• Produce anti-microbial compounds
= toxic to invaders, pathogens
• Aid digestion
• Supply essential growth requirements
• Stimulate immune system
Aid resistance to infection

Question 13

factors governing symbiosis exam

Answer 13

1. No. organisms:
   Increase numbers = shift to parasitism eg poor hygiene
2. Virulence of organisms
   Increase virulence = shift to parasitism
3. Host’s defence / Resistance
   Healthy = high resistance
   Decrease resistance = shift to parasitism

Question 14

what is virulence

Answer 14

the degree or intensity of pathogenicity.i.e. increased virulence-> likely to cause harm and result in parasitism

Question 15

drift

Answer 15

Drift = small antigenic changes
→ alteredprotein
= not effectively recognised by immune system

Question 16

shift

Answer 16

Shift = drastic antigenic changes
→ large scale altered proteins
= not recognised at all by immune system

Question 17

what is the result of shift and drift

Answer 17

major epidemics (or pandemics)

Question 18

transmission of influenza virus

Answer 18

• Air-borne:
– aerosols: coughing, talking, sneezing: ‘flu, chicken pox, mumps, measles etc
– dust: hospitals = nosocomial infection
• Contact: Direct usu. skin to skin; utensils, STI’s
• Vehicle: contaminated food / water: cholera, food poisoning
• Vectors: malaria, trypanosomiasis

Question 19

control of infecious disease from the infectious disease cycle. EXAM

Answer 19

Source: reduce / eliminate
– Eliminate contaminated food or water: food poisoning
– Quarantine carriers and diseased: smallpox
– Destroy animal carriers: mad cow disease, chicken ‘flu HK – Identify reservoir: bats in SARS outbreak
Transmission (KEY ROLE): stop spread one host to next – Change behaviour: HIV protection
– Destroy insect vectors: DDT mosquitoes
– Control animal vectors: cattle: brucellosis, TB
Host susceptibility
– Improve nutrition
– Vaccinate
– Problem with lack of immunocompetence

Question 20

virulence and mode of transmission EXAM

Answer 20

Virulence =intensity of pathogenicity OR degree of ability to cause disease
Affected by ability to live outside host
Eg Common cold:
virulence low / direct contact low level transmission host still active, moves around, spreads virus
cv. Increase virulence, host ill (bed-ridden), transmission drops
Conversely, vector transmission eg African sleeping sickness: host can’t transmit, reliant on vector
= Virulence not connected with transmission

Question 21

Pathogenicity

Answer 21

Pathogenicity

= the ability to cause disease

Question 22

Virulence

Answer 22

Virulence
= degree or intensity of pathogenicity of a microbe&raquo_space; indicated by:
fatality rates
ability to invade host tissues & cause disease

Question 23

1. What are virulence factors?

Answer 23

1.Microbial strategy / Trait
• Product eg toxin
2. Contribute to virulence = virulence mechanism
• Clear connection: virulence infection
3. Plus “Housekeeping” functions
• Derive nutrients, energy for survival in host

Question 24

virulence factors

Answer 24

1. Aid colonisation
2. Allow penetration of host tissue
3. Prevent/reduce host response
4. Cause direct damage eg.toxicity

Question 25

colonisation

Answer 25

Attachment / Adhesion -Non-specific | -Specific

Question 26

give e.g of non-specific attachment

Answer 26

NON-SPECIFIC: SLIME/CAPSULE/GLYCOCALYX 1. dental plague e.g. the attachment of slime layer derive from polysacchride cause the acummulation of the plague 2. glycocalyx the intestinal epithelium hide under glycocalyx of the E.coli->protection

Question 27

give e.g. of specifc attachment

Answer 27

influenza virus protein spikes - the spikes bind to the receptor initiate infection. HA trimer for attachment and NA tetramer for puncture of the wall

Question 28

adheren mechanism

Answer 28

1. pilli for sexual conjugation | 2. fimbrial for adhesions

Question 29

host cell penetration and growth

Answer 29

``` Uptake via • Invasins: bacterial surface proteins: promote ingestion • Endocytosis: non-phagocytic cells Exocytosis: actin tail propulsion • Phagocytosis. e.g. influenza virus:endocytic uptake Measles virus: membrane fusion uptake ```

Question 30

coagulase

Answer 30

coagulates blood

Question 31

kinases

Answer 31

digests fibrin clots

Question 32

hyaluronidase

Answer 32

hydrolyses hyaluronic acid

Question 33

collagenase

Answer 33

hydrolyzes collagen

Question 34

IgA proteases

Answer 34

destroy IgA antibodies=survivall

Question 35

4.Evading the Immune Response | Capsules Virulence protective anti-phagocytic

Answer 35

Capsules Virulence -e.g. Crytococcus neoformans forming capsule, capsule can prevent phagocytosis therefore escape the immune response protective anti-phagocytic

Question 36

5. damaging the host

Answer 36

1. Microbial Toxins i. Exotoxins ii. Endotoxins 2. Pathogenicity Islands

Question 37

describe exotoxins EXAM

Answer 37

``` source: mostly G+ metabolic product: by-products of growing cell chemistry: protein fever: NO neutralized by antitoxin: YES ```

Question 38

e.g. of a disease caused by exotoxin

Answer 38

exfoliative toxin: Scalded skin syndrome caused by the exotoxin of staph.aureus in immuno naive infant

Question 39

microbial exotoxins classification

Answer 39

3 types based on structure & action: 1. A-B 2. Membrane-disrupting 3. Superantigens

Question 40

Microbial Exotoxins: A-B Toxins

Answer 40

Active-binding protein | - B involve in binding, A invove in damage the cell

Question 41

e.g. of A-B toxin

Answer 41

cholera exotoxin | - the exotoxin cause the protein to be inactive result in the disease Vibrio cholerae.

Question 42

membrane disrupting | Exotoxins and e.g

Answer 42

``` Channel-forming (pore- forming) -Phospholipase hydrolysis of membrane: * Destabilises * Destroys integrity e.g.Clostridium perfringens alpha-toxin: phospholipase action causing gas gangrene ```

Question 43

superantigen-exotoxin

Answer 43

Rare strains of Staphylococcus aureus produce TSS-toxin, In the tempon, the Mg stimulate the production of an organism causing peelin skin

Question 44

endotoxin

Answer 44

``` Source: Gram – Metabolic product: Present in LPS of outer membrane Chemistry: Lipid Fever? Yes Neutralized by antitoxin: No ```

Question 45

inflammatory action of endotoxins

Answer 45

1. macrophage ingestes a G- bacterium 2. the bacterium is degraded in a vacuole, releasing endotoxins that induce the macrophage to produce IL-1 3. IL-1 is released by the macrophage into the bloodstream, through which it travels to th ehypothalamus of the brain 4. IL-1 induces the hypothalamus to produce PG, which reset the body's thermostat to a higher temperature, producing fever

Question 46

what is the inflammatory components of G+ bacteria

Answer 46

1. peptidoglycan 2. lipoteichoic acid LTA 3. teichoic acid TA

Question 47

mechnism of pathogenicity islands exam

Answer 47

• Contribute to characteristics of pathogenicity – Absent in non-pathogenic strains • Large segments of DNA – Contain insertion-like sequences = mobile – Encode major virulence factors – Associated with tRNA encoding genes • Pathogens may have >1 PI • Maybe plasmids • Acquired by horizontal gene transfer

Question 48

e.g. of pathogenicity islands

Answer 48

Examples – alter actin microfilaments to mediate adherence – modulate host activities

Question 49

example of pthogenicity island:Protein secretion: Modulates host activities. exam

Answer 49

``` Yersinia pestis (causes plague): Type III secretion system: Function: • delivers effector proteins • secretes plasmid-encoded outer membrane proteins into phagocytic cells Action: • counteracts natural defence mechanisms • helps Y. pestis multiply and disseminate in the host ```

Question 50

endotoxin

Answer 50

Gram –ve: LPS | Gram +ve: Peptidoglycan, LTA,TA

Question 51

Non-specific host defences

Answer 51

1. Physical barriers – Skin / Mucosal membranes / Flushing mechanisms 2. Chemical Barriers – Proteins / pH / Hormones / Others: bile, urea 3. Biological Barriers – Normal flora / Inflammation / Phagocytosis

Question 52

Host factors affecting successful establishment of infection

Answer 52

1. Socio-economic status: - Nutrition - Living conditions: poverty, overcrowding 2. 2. Age: - Very young - Aged 3. Gender 4. Occupation 5. Race 6. Genetic factors 7. Defective immune systems

Question 53

physical barriers

Answer 53

* Skin | * Mucous membranes • Flushing mechanisms

Question 54

defence of skin EXAM

Answer 54

- dry acidic environment: prevent growth of many bacteria - dead, keratinized cells: keratin is hard to degrade, and dead cell diacourage colonization - slouphing of surface cells: remove bacteria that adhere - toxic lipids, lysozyme: protect hair follicles, sweat glands and sebaceous gland - normal microbiota - underlying immune cells (langerhans): combat bacteria that mannage to reach the dermis and tissue below it

Question 55

defenses of mucosal membrane

Answer 55

- thick layer of mucin - trap bacteria before reach the cell - contain antimicrobial compounds such as lysozyme and lactoferrin - MALT mucosal-associated lymphoid tissue

Question 56

Muco-ciliary escalator

Answer 56

move and repel foreign particle

Question 57

what does lysozyme do in mucus

Answer 57

digest peptidoglycan

Question 58

what does lactoferrin do in mucus

Answer 58

sequester iron, prevent growth of bacteria

Question 59

chemical barriers

Answer 59

``` • Antimicrobial factors in body fluids: mucous, tears, saliva – Lysozyme • Proteins – Enzymes – Bacteriocins – Complement – Fibronectin – Cytokines: eg Interferon • Hormones • LowpH • Others – Bile, urea ```

Question 60

Lysozyme Breaks Down __ ?

Answer 60

Gram +ve Cell Walls

Question 61

complement

Answer 61

• Series of 9 serum enzymes, act in cascade • Always present in serum • Activated when Ag/Ab reactions occur • In association with Ab, causes bacterial lysis • Aids phagocytosis >>>>> RESULT: Kills bacterial cells

Question 62

glycoproteins

Answer 62

``` = proteins + polysaccharide moieties eg Fibronectin - Mediatesnon-specificclearance - Coatsforeigncellsclotting - Blocksattachmentofforeignorganismsto epithelial cells >>>>> RESULT: limits colonisation ```

Question 63

cytokines

Answer 63

• Intercellular signal • Bindtoreceptorsoncells • Triggers cellular behaviours: – Initiate signal transduction pathway >> regulates specific transcription, translation events • Soluble small protein or glycoprotein • Can induce production of other cytokines • Produced in response to non-specific stimulus from: – microbes: bacteria, viruses, parasites – cancer – inflammation – action of specific immune cells

Question 64

interferon

Answer 64

• antiviral proteins • formed in response to viral infection • excreted by infected cell • species specific, not virus specific • interesting as anti-viral drug: expensive; genetic engineering >>>>> RESULT: Protects other cells from viral infection

Question 65

Anti-viral Action of Interferon 1

Answer 65

1. virus RNA enters the cell 2. infecting virus replicates 3. the infecting virus induces RNA to produce alpha and beta interferon 4. interferons released by the virus-infected cell bind to plasma membrane of neighbouring uninfected cells inducing them to produce anti-viral proteins (AVPs) 5. new viruses infect neighboring cells 6. AVP's degrade new viral mRNA, inhibiting protein synthesis and replication

Question 66

Biological Barriers

Answer 66

• Normal flora • Inflammation – Acute – Chronic • Phagocytosis

Question 67

acute inflammation

Answer 67

``` – – – Results from tissue injury and infection See redness, swelling, warmth, pain 4 steps: 1. Increasedbloodflowanddilation 2. Riseintemperature 3. Formationoffibrinclot 4. Phagocyticaction >>>>> RESULTS: destruction of invader localisation of infection ```

Question 68

4 steps in acute inflammation

Answer 68

1. Increasedbloodflowanddilation 2. Riseintemperature 3. Formationoffibrinclot 4. Phagocyticaction

Question 69

Acute Inflammation: Capillary penetration

Answer 69

1. damaged tissue 2. inflammatory signals 3. dialation/permeability 4. chemotaxis 5. attaction of pahacytes to site 6. destruction of foreign microbe

Question 70

• Chronic

Answer 70

– Slow | – Intracellular pathogens eg TB, syphilis

Question 71

outcome of phagocytosis

Answer 71

1. nonencapsulated bacterial engulfed by pathocyte and digested 2. bacteria protected by capsule or by M protein cannot be engulfed by phagocytes (e.g. streptococcus phemoniae/pyogenes) 3. pathogens engulfed but produced leukocidin and destroy phagocyte (Staph.aureus, strep pyogenes) 4. pathogens engulfed but gorwn within pjagocyte (e.g. mycobacterium tuberlosis, salmonella typhi)

Question 72

natural killer cells

Answer 72

• Non-phagocytic lymphocytes (more on lymphocytes next lecture) • RecognisecellswithdefectiveMHCclass1protein on cell surface • Result in production of pore-forming perforin proteins and granzymes = lyse target cells = apoptosis • Attackanddestroycells: – Malignant – Containing microbes – Opsonised with antibody

Question 73

Revision: How are Bacteria Classified?

Answer 73

``` 1. Phenetic (phenotype): – Gram reaction and morphology – Carbon sources, energy sources – Electron acceptors (eg. aerobic/anaerobic) 2. Phylogenetic (genotype): – Ribosomal RNA sequence – Other DNA, RNA, protein sequence ```

Question 74

diverse G- bacteria can cause disease

Answer 74

1. proteobacteria - gamma-proteobacteria: Escherichia, salmonella, vibrio, pseudomonus - beta-proteobacteria:neisseria - alpha-proteobacteria: Rickettsia 2. spirochaetes: e.g. treponema

Question 75

Escherichia

Answer 75

- gamma-proteobacteria: - Facultative anaerobic, heterotrophic, G-ve rods - Found in gut of humans and animals -Part of family Enterobacteriaceae: contains many other pathogens: Salmonella, Klebsiella, Yersinia • Widely used in microbiology as a model organism • Motile by peritrichous flagella e.g. e.coli the polar flagellum e.g. pseudomonus is non-motile

Question 76

Transmission of Disease

Answer 76

Transmission of Disease 1.Inoculation =directcontact eg staphyloccal skin infections, STI’s, leprosy, anthrax, Herpes cold sores & genital herpes, tetanus 2. Inhalation = air-borne, ~10um diameter droplets -> respiratory tract eg TB, chickenpox , influenza, diphtheria, Legionnaires disease, meningococcal disease Ingestion = food/water-borne -> gastrointestinal tract eg botulism, food poisoning, typhoid, cholera, viral gastroenteritis, polio Vector-borne = minor = arthropod or mosquito bite ->skin eg plague, malaria, sleeping sickness, Ross River fever, Murray Valley encephalitis Combination = both air-borne & direct contact transmission eg Ebola & Marburg viruses = haemorrhagic fevers involving massive haemorrhage throughout the body

Question 77

Inoculation

Answer 77

Inoculation =directcontact | eg staphyloccal skin infections, STI’s, leprosy, anthrax, Herpes cold sores & genital herpes, tetanus

Question 78

Inhalation

Answer 78

air-borne, ~10um diameter droplets -> respiratory tract eg TB, chickenpox , influenza, diphtheria, Legionnaires disease, meningococcal disease

Question 79

ingestion

Answer 79

Ingestion = food/water-borne -> gastrointestinal tract eg botulism, food poisoning, typhoid, cholera, viral gastroenteritis, polio Vector-borne = minor = arthropod or mosquito bite ->skin eg plague, malaria, sleeping sickness, Ross River fever, Murray Valley encephalitis

Question 80

vector-borne

Answer 80

Vector-borne = minor = arthropod or mosquito bite ->skin | eg plague, malaria, sleeping sickness, Ross River fever, Murray Valley encephalitis

Question 81

combination

Answer 81

Combination = both air-borne & direct contact transmission eg Ebola & Marburg viruses = haemorrhagic fevers involving massive haemorrhage throughout the body

Question 82

Staphylococcal Infections

Answer 82

Transmission: Inoculation, Direct Contact

Question 83

bacterial skin infections

Answer 83

When the stratum corneum is disrupted: – Trauma: abrasion, insect bite, burn... – Maceration due to excess moisture: blisters... – Inflammation: injury, allergy... Two common bacterial pathogens: Staphylococcus aureus – Present in anterior nares of 20-40% of people – Can spread person-person – Usu. colonises nose first then spreads to skin Streptococcus pyogenes (= Group A Streptococcus) Refer to U3L20 − Rarely persists for long − Generally acquired from others − Usu. goes to skin first; later colonises respiratory tract

Question 84

Staphylococcus aureus exam

Answer 84

Staphylococcus aureus – Present in anterior nares of 20-40% of people – Can spread person-person – Usu. colonises nose first then spreads to skin

Question 85

Streptococcus pyogenes

Answer 85

Streptococcus pyogenes (= Group A Streptococcus) Refer to U3L20 − Rarely persists for long − Generally acquired from others − Usu. goes to skin first; later colonises respiratory tract

Question 86

Epidermis: Impetigo exam

Answer 86

Caused by S. pyogenes alone or with S. aureus Does not scar as infection is superficial Resolves spontaneously or with antibiotic treatment

Question 87

Dermis: Folliculitis exam

Answer 87

* Staphylococcus aureus is most common cause of infection and inflammation of hair follicle * Stye = infection of oil gland of Zeis on base of eyelid

Question 88

Furuncles:

Answer 88

Furuncles: | extension of folliculitis

Question 89

carbuncles

Answer 89

coalescence of furuncles; associated chills, fever indicate systemic spread of Staphylococcus

Question 90

Virulence Factors of S. aureus: Cell wall

Answer 90

1. Cell wall components: Capsule / slime: Anti-phagocytic, masks cell, adherence 2. Protein A: Anti-phagocytic, binds host Ig, prevents complement activation 3. Peptidoglycan: Stimulates endotoxin-like activity; attracts polymorphs (abscess formation); inhibits phagocytosis; stimulates complement cascade 4. Teichoic acid: Invasion; mucosal cell attachment

Question 91

action of S.aureus capsule/slime

Answer 91

Anti-phagocytic, masks cell, adherence

Question 92

action of S.aureus protein A

Answer 92

Protein A: | Anti-phagocytic, binds host Ig, prevents complement activation

Question 93

action of S.aureus peptidoglycan

Answer 93

Peptidoglycan: Stimulates endotoxin-like activity; attracts polymorphs (abscess formation); inhibits phagocytosis; stimulates complement cascade

Question 94

action of S.aureus Teichoic acid

Answer 94

4. Teichoic acid: | Invasion; mucosal cell attachment

Question 95

virulence factor os S.aureus:enzymes

Answer 95

Enzymes: 1. B-lactamase : Penicillin; inactivates antibiotic 2. Catalase: Lethal H2O2; protects against killing by oxidative burst in phagocytosis 3. Coagulase Host fibrinogen fibrin coating on Staph. cells clumping; anti-phagocytic 4. DNase: DNA; destroys host nucleic acid 5.Hyaluronidase: Hyaluronic acid; spreading factor 6. lipase: Lipids; affects cell membranes Nucleic acid 7. protease: Proteins

Question 96

S.aureus coagulase production, covert fibrinogen into fibrin

Answer 96

• Clots plasma: Coagulase + prothrombinblood > staphylothrombin + fibrinogenblood > fibrin • Related to virulence: Surrounds Staph cell with fibrin meshwork: Increased diameter > ineffective phagocytic uptake = protective persistence infection

Question 97

Enterotoxins of S.aureus | toxins of S.aureus as part of virulence factors

Answer 97

GIT, cause food poisoning

Question 98

cytotoxic haemolysins (toxins of S.aureus as part of virulence factors)

Answer 98

alpha: erythrocytes, skin beta: erythrocytes, sphingomyelin alpha and gamma: erythrocytes

Question 99

leukocidin (toxins of S.aureus as part of virulence factors)

Answer 99

Cytotoxic; inhibits phagocytosis by granulocytes

Question 100

Exfoliative toxins A & B (toxins of S.aureus as part of virulence factors)

Answer 100

Surface layers of skin; shedding

Question 101

Toxic shock syndrome toxin-1 (toxins of S.aureus as part of virulence factors)

Answer 101

Systemic effects, causes fever, shock

Question 102

virulence factors of S.aureus: toxin

Answer 102

enterotoxins: GIT, cause food poisoning cytotoxic haemolysins : alpha: erythrocytes, skin beta: erythrocytes, sphingomyelin alpha and gamma: erythrocytes leukocidin: Cytotoxic; inhibits phagocytosis by granulocytes Exfoliative toxins A & B:Surface layers of skin; shedding Toxic shock syndrome toxin-1:Systemic effects, causes fever, shock

Question 103

S. aureus Leukocidin | leuko = white; cide = kill: kills white blood cells eg PMNs, neutrophils

Answer 103

Postulated actions: • causes polymorphonuclear leukocyte (PMN) lysis • low concentrations mediate PMN apoptosis: bind directly to mitochondrial membranes • creates pus: pus contains pus cells = necrotic PMNs • tissue necrosis results from release of reactive oxygen species from lysed PMNs • release of granule contents from lysed PMNs ->inflammatory response ->tissue necrosis >>>>> RESULT: cell death, pus formation

Question 104

S. aureus Exfoliative Toxin: | Ritter’s Disease aka Scalded Skin Syndrome

Answer 104

toxin-mediated disease: caused by exfoliatin toxin produced by certain strains of S. aureus Occurs in young children: spontaneous recovery in 7-10d; scarring absent Taken from: Emond et al Secondary complicating bacterial infections sometimes cause more serious disease

Question 105

STI: Chlamydia Transmission: Intimate Direct Contact exam

Answer 105

• Acquired via intimate contact • Usu. microbes unable to survive outside human body • Several important bacterial causes of STI: – Neisseria gonorrhoea,Treponema pallidum(syphilis), Chlamydia trachomatis • Several important viral causes of STI: – HIV, genital herpes, papilloma virus, HepB • Globally 300 million new cases/year • Many unreported, undiagnosed ->sequelae = sterility, scarring

Question 106

why chamydial infection increase from yrs to yrs

Answer 106

1. Increased recognition, better testing → increased diagnoses → increased notifications 2. Underestimate because often asymptomatic

Question 107

Chlamydial Infection

Answer 107

``` Males: • Painful urination • Inflammation • Discharge: mucopurulent = v. similar to gonorrhoea Females: • Slight discharge, 80% asymptomatic • Inflammation of cervix • Burning on urination ```

Question 108

Who is at risk?

Answer 108

Who is at risk? • People in contact with asymptomatic, infected persons • People with multiple partners • Newborns of infected mothers

Question 109

Chlamydia trachomatisEXAM

Answer 109

• Small

Question 110

C. trachomatis Bind to Mucosa

Answer 110

``` Problems: • scarring ♀ blocks Fallopian tubes ♂ blocks urethra, vas deferens • infection spreads - salpingitis PID Result >>> infertility ```

Question 111

TB transmission: aerosols

Answer 111

• Oldest documented infectious disease • ‘Great White Plague’ / ‘Consumption’ (Satine in ‘Moulin Rouge’) • Linked to poor sanitation / bad living conditions • Chronic, slowly progressing infection – usu. of lungs – also: kidneys, spine, brain • Incidence: – 16th-18th C: 25% with TB died – Today • Globally: Each year: – 2 billion infected (1/3 world’s pop.) – 2 million die • Australia: 1300 new cases / year

Question 112

contributors to increased incidence

Answer 112

• Immigration from endemic TB areas • The human immunodeficiency virus epidemic – AIDS: infection with atypical strains • Antibioticresistance – development of multi-drug resistant TB • TBtransmissionininstitutionalsettings – hospitals and prisons • Reducedemphasisoncontrol&prevention – Deterioration of the infrastructure for TB services: • No mobile clinics in Australia – No new drugs – Need for more research

Question 113

causative organis for TB

Answer 113

Mycobacterium species • Usu. M. tuberculosis • M. bovis: cattle assoc’d: – Vaccination / herd testing / milk pasteurisation • Atypical strains (eg M. avium): – Immunosuppression eg AIDS, cancer drugs – RT defect eg COAD

Question 114

Pathogen: | Mycobacterium tuberculosis

Answer 114

``` • Aerobe • Fastidous • Slow-growing: 12-24hours/generation • Waxy lipids (mycolic acid) in cell wall – 40% lipid Hydrophobic – Resistant to disinfectants and stains – Acid fast ```

Question 115

Identification

Answer 115

``` dentification Specimen = Sputum/phlegm – Stain: Acid fast rod in smear – Culture: Lowenstein Jensen medium (SLOW) • Confirmatory • Drug resistance – Molecular techniques (QUICK) • PCR ```

Question 116

establish of TB infection important NO toxins produced

Answer 116

Enters URT in small aerosol droplets tubercle

Question 117

phagocytosis: selective uptake

Answer 117

* Preferential uptake via complement and mannose receptors * Inhibits uptake via Fc receptor * Inhibits phagosome / lysosome fusion * Possibly escapes from phagosome into cytoplasm

Question 118

Tubercles

Answer 118

Tubercles = Area of dead tissue surrounded by layer of macrophages and T lymphocytes • Walled off, calcified • Interior ‘cheese-like’: caseous necrosis – Trap bacteria

Question 119

Essentials of CMI response to TB EXAM

Answer 119

• T helper cells and macrophages interact via receptors and cytokines • Th1 cells secrete INTERFERON GAMMA (IFN-y) • Macrophages secrete TUMOUR NECROSIS FACTOR (TNF) • IFN-y plus TNF → OPTIMAL MACROPHAGE ACTIVATION • Macrophage activation → ↑↑ proteolytic enzymes ↑↑ ROI ↑↑ RNI some tubercle bacilli killed → giant cells & epithelioid cells • Granulomas form – consist of activated macrophages, T helper & T cytotoxic cells – may contain the infection

Question 120

Outcomes of Cell-mediated Immune Response

Answer 120

• Control (latent infection): – Activated macrophages kill M. tuberculosis • Tubercles calcify = granuloma • No symptoms, not contagious • Reactivation ~20yrs / immunosuppression OR • Uncontrolled (TB disease): – Insufficient immune response • Centre of tubercles liquefy • Bacteria coughed up in sputum • Spread to blood, organs • 50% mortality rate

Question 121

Outcomes of Cell-mediated Immune Response control (latent infection)

Answer 121

• Control (latent infection): – Activated macrophages kill M. tuberculosis • Tubercles calcify = granuloma • No symptoms, not contagious • Reactivation ~20yrs / immunosuppression

Question 122

Outcomes of Cell-mediated Immune Response uncontrolled (TB disease )

Answer 122

``` • Uncontrolled (TB disease): – Insufficient immune response • Centre of tubercles liquefy • Bacteria coughed up in sputum • Spread to blood, organs • 50% mortality rate ```

Question 123

latency

Answer 123

• Bacteria survive: – inside walled-off lesions in lungs – in lung-associated lymphoid tissue – in other sites • Reactivation up to 20 years later

Question 124

TB disease Pulmonary Symptoms

Answer 124

* Chronic, bad cough: lasts > 3 weeks * Chest pain * Coughing up blood/sputum * Weakness or fatigue * No appetite weight loss * Chills, fever, night sweating

Question 125

Symptoms

Answer 125

cough and weight loss

Question 126

Extrapulmonary TB

Answer 126

Active TB in : – Kidneys – Skin – Lymph nodes – Bones / joints – Brain

Question 127

screening for TB

Answer 127

1. ChestX-ray 2. Tuberculintest(Mantoux): – Intradermalskininoculationoftuberculo- protein PPD – Indicatescell-mediatedhypersensitivity – DetectslatentandactiveTBorsuccessful BCG vaccination -ve result: • No skin reaction after 2d • Never infected with M. tuberculosis • Sometimes false –ve in tuberculous meningitis

Question 128

prevention of TB

Answer 128

``` • Limit transmission • Improve living conditions – Housing – Nutrition – Social deprivation • BCG (Bacille Calmette-Guérin) vaccine ```

Question 129

BCG Vaccination

Answer 129

• Attenuated vaccine: Live strain of M. bovis reduced in virulence • Local reaction at site within 2-6 weeks: Papule ulcerates, heals, scar • Initiates cell-mediated immune response • Administration: – Developing countries / endemic areas: children at birth – Developed countries: high risk individuals: contacts, healthcare workers, teachers, immigrants from endemic countries – Not used for: • Immunosuppressed people • Asymptomatic HIV +ve – Variable effectiveness: • Research studies: UK 70% / 20years; India 0 - 90% >>> BCG provides some protection against TB because: • M.tuberculosisandM.bovisBCGsharesomeantigenicepitopes • MemoryTcellsconferprotection

Question 130

treatment TB

Answer 130

• Isoniazid,rifampicin,pyrazinamide ethambutol • Two or more drugs given together – Minimises development of resistance • Long-term: ~1year – Poor compliance – Resistance • Spontaneous chromosomal mutations • 2007 in Aust.: >11% strains showed some resistance (Lumb et al)

Question 131

The clinical specimen should be:

Answer 131

The clinical specimen should be: 1. Appropriate and adequately represent the diseased area 2. Of sufficient quality /quantity for all tests 3. Free of contamination 4. Collected into appropriate containers 5. Obtained before antibiotics are administered (if possible) 6. Accompanied by notes from the physician

Question 132

Transport

Answer 132

``` Transport Must be quick because pathogens can - Die quickly outside the body - Be overgrown by contaminants Minimise time lag between sampling and testing using: • special transport media • preservatives • dip slides • refrigeration/freezing ```

Question 133

Laboratory reception:

Answer 133

Laboratory reception: Need good documentation on receipt of specimen, Assignment of ID no. and labeling

Question 134

Examination:

Answer 134

Examination: - Macroscopic - Microscopic - Using specific lab tests

Question 135

Additional tests and reporting

Answer 135

``` Additional tests and reporting Initial report Preliminary report Presumptive diagnosis Final report Confirmatory diagnosis Supplementary report ```

Question 136

B. Laboratory Testing Techniques

Answer 136

``` B. Laboratory Testing Techniques I. Microscopic methods II. Cultural methods III. Serological/immunological methods IV. Molecular methods V. MALDI-TOF VI. Typingsystems:strainswithinspecies VII. Antibiotic sensitivity testing ```

Question 137

B. Laboratory Testing Techniques:I. Microscopic methods

Answer 137

* Unstained preparations * Simple stains: Gram * Special stains: specific features * Immunofluorescence

Question 138

I. Microscopic methods: | General stains

Answer 138

Haemophilus influenzae present in CSF seen with Gram stain Fungal cell staining pink with the H&E stain used in histology

Question 139

I. Microscopic methods: | Special stains

Answer 139

Ziehl-Neelsen’s acid fast stain shows the presence of Mycobacterium in a sputum sample Negative staining of a CSF sample with India ink shows encapsulated Cryptococcus cells

Question 140

I. Microscopic methods: | Immunofluorescence

Answer 140

M. tuberculosis - labelled with fluorescent antibod

Question 141

B. Laboratory Testing Techniques cont. | II. Cultural methods:

Answer 141

These allow: 1. Isolation on solid media 2. Identification through morphological and biochemical characteristics 3. Pure isolate for other testing (eg. biochemical tests, antibiotic sensitivity tests)

Question 142

Three Types of Culture Media:

Answer 142

1. Enrichment media • For low numbers or fastidious organisms • Can be liquid or solid • Enriched with blood, tissue infusions, etc

Question 143

Three Types of Culture Media:

Answer 143

2. Selective media Separation of pathogen from mixture Selective ingredients - antibiotics, dyes, bile salts etc Mannitol salt agar; Staphylococci can tolerate high salt media while most other bacteria are inhibited

Question 144

Three Types of Culture Media:

Answer 144

3. Indicator media • Identify particular colonies among a mixture • Contain sugars or other substrates and dyes • Indicator media are usually selective as well Chromogenic agar MacConkey agar – selective and indicator medium

Question 145

Culture: Biochemical Tests

Answer 145

• Series of tests allow presumptive ID – Sugar usage – Chemical compound usage Test for indole - separate enterics such as E. coli (Ind+) from Enterobacter (Ind-) Salmonella in Rappaport - Vassiliadis medium +ve (left) & -ve (right) Fermentation reactions - used to separate enterics

Question 146

Culture: Biochemical Tests

Answer 146

Multitest systems combine tests in a single kit eg. API

Question 147

Limitations of culturing exam

Answer 147

Limitations of culturing • Incubation time delays diagnosis and treatment • Labour-intensive • Improvements include automation and computer analysis

Question 148

Laboratory Testing Techniques cont

Answer 148

III. Serological / Immunological methods: eg precipitatin, haemagglutination, complement fixation, ELISA • GenerallyusedtodetectvirusesorAbtoviruses • Useful for organisms that are difficult to culture or dangerous • Disadvantages: - retrospective - +ve result ≠ active infection

Question 149

Laboratory Testing Techniques cont | IV. Molecular methods (Genus & species ID)

Answer 149

1. Probe for genes - specific virulence factors of pathogen - commercially available - quick, accurate so long as gene present in high numbers 2. DNA Amplification - increase copies of gene before probe - difficult/slow, dangerous pathogens 3. Microarrays - simultaneous screening for different pathogens

Question 150

IV. Molecular methods (Genus & species ID)Advantages and dis

Answer 150

``` IV. Molecular methods (Genus & species ID) • Advantages - highly automated - high sensitivity & specificity • Disadvantages - contamination->false +ve - inhibition->false –ve - can only detect known microbes - expensive equipment and reagents ```

Question 151

V. MALDI TOF | Matrix-Assisted Laser Desorption/Ionisation Time-Of-Flight

Answer 151

* MALDI TOF detects abundant housekeeping proteins in the sample, especially ribosomal proteins * Developed for bacteria; can also be used for fungi/yeasts; not very good for viruses as they don’t have much protein * Now adopted by many large diagnostic labs worldwide due to speed, sensitivity and low cost

Question 152

MALDI TOF limitation

Answer 152

Limitations: • Doesn’t work for viruses • Only as good as your database • Can’t handle mixed samples where there are >1 organism present • Doesn’t work on solid samples (stool; tissue)

Question 153

VI. Typing systems - strain within species

Answer 153

``` • Tracesourceofoutbreak • Biochemical,culture,genetic - biotyping – phenotypic markers - serological typing – agglutination - molecular typing – restriction digestion-based eg. Pulsed Field Gel Electrophoresis (PFGE), sequence-based, eg. MultiLocus Sequence Typing (MLST) ```

Question 154

VII. Antibiotic sensitivity testing Identified pathogen – which antibiotic?

Answer 154

• Tests ensure appropriate treatment -> minimise severity of disease -> shorten recovery time • Especially valuable for organisms with unpredictable AB sensitivity

Question 155

C. Treatment

Answer 155

C. Treatment • If disease is life threatening – initiate antibiotic therapy without waiting • Antibiotic sensitivity test: - confirm treatment OR - recommend more effective therapy

Question 156

• Importance of fungi to human health

Answer 156

* Importance of fungi to human health * Poisonous mushrooms (mycetism) • Food spoilage fungi and mycotoxins • Allergenic fungi and hypersensitivity • Commensal and pathogenic fungi

Question 157

fungi

Answer 157

* Eukaryotic * No chlorophyll * Moulds / yeasts * Usually found in moist dark habitats * Usually aerobic, though some are anaerobic • Cell walls contain chitin * Reproduce by spores

Question 158

Fungal nutrition

Answer 158

Fungal nutrition • Heterotrophic = other feeding • Absorbtive nutrition - digest then ingest their food • Can live off dead matter = saprotrophic • Or living matter - harm host = parasites - help host = mutualists (symbionts)

Question 159

Fungal classification | - where fungi fit with other organisms

Answer 159

Most fungi fit other place | Microsporidia are considered to be fungi as well despite a different phylogenetic placement

Question 160

In fact, fungi are closer to animals than to plants...

Answer 160

...which helps explain why fungal diseases are so difficult to treat

Question 161

1. Mycetisms

Answer 161

``` Amatoxins • LD50 = 0.1 mg/kg • Damage the intestine, kidney and liver, by inhibiting RNA polymerase • Current treatments: 1) remove toxin from system 2) increase excretion of toxin 3) supportive care ```

Question 162

2. Food spoilage fungi and mycotoxins | Fungi can grow on and damage all types of foods – is this a problem?

Answer 162

Yes – especially if they make mycotoxins...

Question 163

Mycotoxicoses

Answer 163

``` Acute • moderate-high levels toxin • specific, observable disease Chronic: • low-moderate levels of toxin • weight loss, infertility, failure to thrive Mycotoxin-associated diseases: • low-very low levels of toxin • general immunosuppression, increased susceptibility to infectious disease ```

Question 164

Aflatoxins

Answer 164

Aflatoxins • First discovered as “Turkey X disease” • Aflatoxin = Aspergillus flavus toxin • Most potent natural carcinogen known; associated with high levels of liver cancer in some developing countries • Mycotoxins could be potential bioterrorist agents

Question 165

3. Allergenic fungi and hypersensitivity

Answer 165

``` 3. Allergenic fungi and hypersensitivity • Main genera causing problems: § Aspergillus § Penicillium § Alternaria § Cladosporium • Grow under damp conditions and make allergenic spores and volatiles ```

Question 166

4. Commensal and pathogenic fungi – the discipline of medical mycology

Answer 166

* Superficial, cutaneous and subcutaneous mycoses – infect skin and underlying tissue * Invasive fungal infections - The “Big Three”: * Candidiasis * Aspergillosis * Cryptococcosis

Question 167

Superficial mycoses

Answer 167

• Limited to the outer surface of hair or skin • Infection of hair shafts known as piedras • Some superficial mycoses known as tineas (Latin for grub or worm) • Generally limited to tropics; Prevented by good personal hygiene; Treated with cleansing agents Black piedra on hair shaft Tinea versicolor caused by Malassezia furfur

Question 168

Cutaneous mycoses: Dermatomycoses, (= ringworm, tinea)

Answer 168

``` Involve hair, skin and nails and evoke various cellular responses Tinea corporis – ringworm of the body Tinea capitis Ringworm of the scalp hair Tinea pedis – athletes foot ```

Question 169

``` Dermatomycosis (cont) Tinea unguium – ringworm of the nails Tinea cruris – ringworm of the groin, or “jock itch” ```

Answer 169

Tinea unguium – ringworm of the nails Tinea cruris – ringworm of the groin, or “jock itch”

Question 170

The fungi that cause dermatomycoses

Answer 170

• “Dermatophytes” : Trichophyton, Microsporum, Epidermophyton • Characterised by distinctive spore structures • Easily passed from person-to-person via infected surfaces (eg locker rooms, showers)

Question 171

Clinical aspects of dermatomycoses • Blister-like lesions dry to leave scaly ring • Without treatment may get hair loss, change of hair colour, local inflammatory reactions • Fungi shed on flaking skin and transmitted by direct contact and via intermediates • Can be highly adapted to humans of transmitted from animals or soil • Treat by changing environment • Griseofulvin from Streptomyces griseus used for severe cases

Answer 171

• Blister-like lesions dry to leave scaly ring • Without treatment may get hair loss, change of hair colour, local inflammatory reactions • Fungi shed on flaking skin and transmitted by direct contact and via intermediates • Can be highly adapted to humans of transmitted from animals or soil • Treat by changing environment • Griseofulvin from Streptomyces griseus used for severe cases

Question 172

Subcutaneous mycoses

Answer 172

Subcutaneous mycoses • Caused by numerous soil fungi - introduced via puncture wounds; not spread from person-to-person • Disease develops very slowly with fungi spreading along lymphatic channels - produce subcutaneous nodules that can drain to the skin surface • Generally difficult to treat - some treated with antifungals; may require surgical excision • Diagnosis is important as some bacterial infections mimic subcutaneous mycoses

Question 173

Types of subcutaneous mycoses

Answer 173

• Chromoblastomycosis – Caused by black moulds that exist worldwide • Maduromycosis – Caused by Madurella mycetomatis; destroys subcutaneous tissue – Often called a eumycotic mycetoma (fungal tumor) • Sporotrichosis – Caused by Sporothrix shenkii; can spread throughout body

Question 174

Invasive Fungal Infections (IFIs)

Answer 174

• Few fungi can cause IFIs and these are mostly rare or geographically confined • The Big Three of global importance are: 1. Aspergilus 2. Candida 3. Cry[tococcus

Question 175

Aspergillus - Aspergillosis

Answer 175

* Primarily Aspergillus fumigatus (~85%) and A. flavus (~5%); other Aspergillus sp. ~5% * Acquired from the environment as Aspergillus makes millions of tiny spores

Question 176

Aspergillus - Aspergillosis

Answer 176

• Aspergillosis is an opportunistic infection – gets more serious with the level of immunocompromise of the host – Aspergilloma (fungus ball) – Invasive pulmonary aspergillosis – Disseminated aspergillosis

Question 177

IFIs: Candidiasis

Answer 177

• Candida albicans and other Candida species cause candidiasis • Single celled yeast that often forms pseudohyphae • Is a commensal so can be acquired endogenously • Can be passed from person-to-person • 4th most common cause of bloodstream infections in hospitals

Question 178

Candidiasis takes many forms

Answer 178

• Candidiasis of the vagina = vulvocandidiasis • Candidiasis of the mouth = oral candidiasis or thrush • Candidiasis of skin - fingers (paronychia) and nails (onychomycosis)

Question 179

Candidiasis cont.

Answer 179

• Chronic mucorcutaneous candidiasis • Disseminated candidiasis following immuno- suppression, surgery, severe burns, drug abuse

Question 180

Cryptococcosis

Answer 180

• Caused by two medically important species of Cryptococcus : - C. neoformans - C. gattii • Both species have a large capsule, which is an important virulence factor • Cause cryptococcal pneumonia, cryptococcal meningitis and meningoencephalitis

Question 181

Process of cryptococcal infection

Answer 181

* Acquired from the environment (trees, soil, guano) * The first site of infection is the lungs * From there it can disseminate to other parts of the body, particularly the brain

Question 182

Pathogenic Cryptococcus species

Answer 182

``` 1.Cryptococcus neoformans • Opportunistic • Major AIDS pathogen • Worldwide 2.Cryptococcus gattii • Primary pathogen • Restricted distribution • Important in Australia ```

Question 183

Diagnosis and treatment of fungal infections

Answer 183

• Diagnosisdonebycultureand microscopy • Todayimmunologicalandmolecular techniques are often used to speed up diagnosis – eg ELISA with fungus-specific antibodies or PCR with fungus-specific primers (will discuss these further in the lecture on clinical microbiology) • Treatmentisdifficultastherearefew effective anti-fungals (amphotericin, azoles, echinocandins) - Often toxic since fungal cells are quite like our own

Question 184

Factors contributing to the emergence of infections Change in the ecological niche or global environment

Answer 184

Change in the ecological niche or global environment - Weather patterns (droughts, floods), deforestation - Hantavirus disease: increase mouse population after heavy rainfall 1991-92 (El Niño phenomenon); first ever outbreak of Hantavirus pulmonary syndrome - Cholera: El Niño phenomenon of 1997-98 large areas Africa flooded

Question 185

Factors contributing to the emergence of infections | ! Human behavior

Answer 185

! Human behavior - AIDS epidemic in the wake of sexual behaviors and IV drug users - Population growth: overcrowding, poor sanitation (cholera) - Population shifts and urbanization: disturb natural habitats & increase human contact remote environments- SARS - Travel, globalization of world commerce: SARS - Cultural practices: ritual preparation of bodies for burial (Ebola)

Question 186

Factors contributing to the emergence of infections | ! Technology applied to industry

Answer 186

! Technology applied to industry - Enterohemorhagic E. coli: “hamburger diseases” - Viral transmission with medical use of blood and tissues

Question 187

Factors contributing to the emergence of infections ! Microbial adaptation and evolution

Answer 187

! Microbial adaptation and evolution - Antibiotic resistance: vancomycin resistant enterococci (VRE) post-operative hospital patients, UTIs, septicaemia, wound infections - Bird flu

Question 188

Factors contributing to the emergence of infections | ! Relaxation of public health controls

Answer 188

Multi-drug resistant tuberculosis

Question 189

Factors contributing to the emergence of infections | ! Bioterrorism

Answer 189

- Smallpox, Anthrax

Question 190

Severe Acute Respiratory Syndrome-SARS

Answer 190

! Viral respiratory illness caused by SARS-associated coronavirus (SARS-CoV) ! First reported in Asia in February 2003 ! Outbreak contained by end of 2003 =

Question 191

Symptoms of SARS

Answer 191

! High fever, headache, discomfort, body aches ! 10-20 percent of patients have diarrhea ! After 2 to 7 days, may develop a dry cough ! Most patients develop pneumonia

Question 192

Transmission of SARS

Answer 192

! close person-to-person contact - Primarily healthcare workers and household members - Infrequent instances of community transmission ! respiratory droplets when infected person coughs or sneezes - Fecal-oral - Fomites ! Where did SARS come from: jumped from animal host? - SARS virus not related to other coronavirus subfamilies

Question 193

SARS Containment Strategies

Answer 193

! Locally - Home quarantine - Hospital closures - School closures ! Internationally - Travel advisories - Health Alert Notices - Screening departing airline passengers - Information to passengers arriving from affected areas

Question 194

Bird Flu- definition

Answer 194

! Viral disease affecting respiratory, enteric or nervous system of many kinds of poultry and birds ! Can be a virulent and acute disease with a short course and extremely high mortality ! Recognised in birds over 100 years ago, widespread in 1930s (‘fowl plague’), then sporadic and localised

Question 195

! Influenza A: causes most influenza in humans ! All Influenza A subtypes are present in birds, particularly waterfowl (principal reservoir) ! Influenza pandemics often caused by hybrid viruses - combination of avian & human viral genes (antigenic shift) ! Typically avian species need a period of adaptation to human host- limited ability to directly infect humans

Answer 195

T

Question 196

seasonal H1N1

Answer 196

easily spread rarely fatal

Question 197

H5N1

Answer 197

spreads slowly often fatal

Question 198

Bird Flu and Humans

Answer 198

! Guangdong Province, China (1996): H5N1 virus in ducks ! Hong Kong (1997):H5N1 virus chickens and humans - First example avian influenza transmisson birds to humans - 18 people hospitalised, 6 deaths ! Hong Kong (1999), Avian influenza H9N2 two children, both recover ! Netherlands (2003) H7N7 virus poultry workers and families - More than 80 cases reported, 1 death

Question 199

Why are we concerned? H5N1

Answer 199

!Human to human transmission observed but still inefficient. What if: 1) recombination with readily transmissible human strain? 2) mutation (probably of H5)? !H5N1 in pigs, are a ‘breeding ground’ for human and avian virus recombinations !Virus is in migratory birds !Worst case scenario: Initial estimates predicted 150 million deaths!!!

Question 200

Swine Flu! (Pandemic H1N1/09 virus)!

Answer 200

!First reports outbreak in March 2009 (Mexico City) ! novel Influenza A H1N1 strain ! Reassortment of 4 known influenza A strains (1 human, 1 avian, 2 swine) !Transmission is human to human (not from pigs) ! disease generally mild (compared to H5N1); death rate ~1%

Question 201

Treatment for swine flu

Answer 201

!Tamiflu, Relenza ! global stockpiles are too small ! production has been increased: but can we make enough? ! drug resistance?

Question 202

Ebola

Answer 202

Ebola ! RNA virus of the filovirus family, 5 subspecies identified ! Zaire Ebola virus cause of current epidemic, ~70% mortality rate ! Human to human transmission occurs through direct blood or other body fluids of an infected human or other animal contact with infected bodily fluids !Incubation period ~11 days, diagnosis by PCR ! Symptoms non-specific- fever, weakness, diarrhoea; internal external bleeding, death from fluid loss/organ failure ! no licensed prophylaxis or treatment; supportive

Question 203

How can we deal with emerging and re-emerging infections?! exam

Answer 203

! Enhanced surveillance (e.g. SARS, bird flu)! ! ! ! More effective control measures- new drug and vaccine development (e.g tuberculosis) ! !Improvements in health standards: sanitation, living conditions (e.g cholera) ! Increased education into the risk and spread of infectious diseases (e.g HIV/AIDS, Ebola) ! !

Question 204

Why did it work?! ! the small pox vaccination and eradication

Answer 204

" Effective vaccine (life-long immunity)! ! " No animal reservoir! ! " No subclinical infections, no carriers! ! " One Variola serotype! ! " Major commitments by governments!

Question 205

Aim of vaccination (immunisation ) exam

Answer 205

* Induce specific immunity to protect against infection/disease! * Induce protective immunity without immunopathology! * Eradication of major diseases in which humans are the only natural host! * Immunisation can be ACTIVE or PASSIVE!

Question 206

Passive Immunization!

Answer 206

• Confer protective immunity by transfer of specific antibodies! ! • Rapidly effective but short lived life of antibody! ! • No specific immunological memory! ! • Immunity can be acquired either naturally or artificially !

Question 207

Passive Immunization! | Natural Process!

Answer 207

Natural Process! – Transplacental transfer! – IgA in colostrum during breastfeeding! E.g. Maternal Abs to diptheria, tetanus, streptococci, rubella, mumps and poliovirus!

Question 208

Passive Immunization! | artificial

Answer 208

artificial • Injection of recipient with preformed antibodies! ! • Several conditions warrant the use of passive immunization! ! – Deficiency in synthesis of Abs (agammaglobulinaemia, hyper IgM syndrome)! ! – Exposure to a disease that will cause complications (e.g. child with leukemia exposed to varicella or measles)! ! – Protection from poisonous snakes (anti-venom) and spider bites!

Question 209

Passive Immunization! | Associated risks!

Answer 209

Associated risks! • Immunization with Abs of different species (eg. horse) results in anti-isotype Abs (“serum sickness”)! • May lead to immune complexes depositing in blood vessel walls and tissue-> tissue and organ damage!

Question 210

Active Immunisation! ! | !

Answer 210

• elicit long lasting, protective immunity in individuals ! ! • Eliminate pathogen (where possible)! and in the community (“herd immunity”)! • Can be achieved by natural infection or it can be acquired artificially by the use of VACCINES!

Question 211

Criteria for useful active vaccine:! ! exam

Answer 211

Criteria for useful active vaccine:! ! ! Safe- low risk of side effects, disease! ! Effective- stimulate good immunity in individuals at risk and ! !interrupt transmission of disease; eliminate disease if possible! ! !Long-lasting immunity! ! !Cheap and readily available! ! ! Stable! ! !Easily administered!

Question 212

Killed Inactivated Vaccines! ! | !

Answer 212

! Micro-organisms killed by physical or chemical inactivation ! !(eg formaldehyde)! ! !eliminate infectivity without affecting antigenicity! ! - Examples:e.g.SalkPoliovaccine(Inactivatedpoliomyelitis(IPV): poliovirus type 1, type 2 and type 3; monkey kidney cells, inactivated with formaldehyde)! - cholera, HepA!

Question 213

Killed Inactivated Vaccines adv and dis exam

Answer 213

advantage: safe from reversion to virulence! !"acceptable for immuno-compromised individuals! !"stable for transport and storage! disavantage " less effective than live vaccines (cell-mediated I.R)! !"multiple doses required ! !"requires adjuvants to enhance responses!

Question 214

Live Attenuated Vaccines!

Answer 214

! Micro-organisms lose pathogenicity but retain capacity for transient growth in host! ! ! Extensive culture in “abnormal” media- accumulation of many mutations; or targeted mutations! ! ! Examples: Sabin polio vaccine: passage of virus through monkey kidney cells (e.g. 57 independent mutations in Sabin 1 strain)! - measles, mumps, rubella, BCG!

Question 215

Live Attenuated Vacci

Answer 215

Advantage "“authentic” immune response elicited! !! !"long-term protective immunity (replicate)! !! !"usually single-dose, no adjuvants! !! !"transfer non-immune contacts (consent?) disvantgae !" possible reversion virulent form (1 in 4 mill for Sabin) ! !"complications similar natural disease! !! !"growth media/culture cells produce adverse reactions! !! !"limited shelf life; refrigeration in tropics!

Question 216

attenuated VS inactivated vaccines

Answer 216

killed virus vaccine need multipe dose to amplify | live virus vaccine have natural amflification

Question 217

Attenuated vs Inactivated vaccines: The Polio Story!

Answer 217

Polio: major killer in 1950s! !Salk vaccine (1954)- inactivated poliovirus! !"injected, very safe, high levels circulating IgG, little mucosal immunity! ! " ∴ stops paralysis, not virus spread in GI tract (virus can infect others)! ! Sabin vaccine (1961; OPV) - attenuated poliovirus ! !"oral vaccine; stimulates high level IgA, control virus GI, limit spread! BUT: ! !"some Sabin vaccine-induced polio cases (8-10 per year in USA)! !"countries don’t use Sabin, Polio effectively controlled! !"since 2005 in Oz only inactivated Salk vaccine used in children!

Question 218

Other vaccine types (in use)! ! !Subunit vaccines (purified macromolecules)! ! a) Toxoids! !

Answer 218

a) Toxoids! ! "Exotoxins from organisms chemically inactivated (formaldehyde)! "Develop Abs to toxins, neutralise effect of pathogen

Question 219

e.g. DTPa

Answer 219

e.g. DTPa: Diptheria toxoid, tetanus toxoid, pertussis toxoid (+ other components of Bordetella pertussis)! ! - 3 doses (im) before 6 months, booster at 4 years! - second booster with adult formulation at 12-17 years

Question 220

Other vaccine types (in use)! ! !Subunit vaccines (purified macromolecules)! Recombinant or purified antigens !

Answer 220

Recombinant or purified antigens ! - Cloned genes expressed in bacteria, yeast or mammalian cells ! - Very safe, limited CTL response (processed as exogenous proteins)! - Generally require adjuvants!

Question 221

Subunit vaccines: Examples! 1Recombinant proteins! 2.Purified proteins !

Answer 221

Recombinant proteins! HepB: recombinant hepatitis B surface antigen (HBsAg) protein! ! !Purified proteins ! Influenza vaccines: Fluvax, one of 7 available in Australia! ! - haemagglutinin of each of the 3 recommended strains.!..

Question 222

Other vaccine types (in use)! ! !Virus-like particles! !

Answer 222

!Virus-like particles! - viral protein(s) derived from structural proteins of a virus. ! - resemble virus but lack viral nucleic acid: non-infectious. ! ! - as vaccines effective eliciting T and B cell immune responses. ! ! - Human papillomavirus & Hepatitis B vaccines approved for use!

Question 223

Todays Vaccine Challenges!

Answer 223

• Millions of people worldwide die from malaria, tuberculosis and AIDS! • No effective vaccines for these diseases; Why?! • New vaccine approaches: improve current vaccines and develop new ones! • Lower vaccine costs and availability! • Using knowledge of how immune system works to develop new vaccines!

Question 224

cellular compartment and virus replication

Answer 224

 All virus replication occurs within the host cell • The cell provides: – Nucleotide substrates – Energy – Enzymes – Other proteins  All virus genomes must produce mRNA which can be translated by host ribosomes

Question 225

Virus life-cycle

Answer 225

Viruses need to: 1. Get their genome into a host cell 2. Produce mRNA; leads to viral protein synthesis 3. Replicate their own genome 4. Assemble new virions and leave the cell

Question 226

Biosynthesis

Answer 226

Biosynthesis ß synthesis of viral mRNA ß synthesis of viral proteins ß synthesis of viral nucleic acids

Question 227

1.Attachment to host cells

Answer 227

Attachment to host cells • Mediated by interactions between specific cellular receptors and proteins on the virion surface • One virus may use more than one cellular receptor • A cellular receptor may be shared by multiple viruses • Co-receptors can be involved e.g. HIV uses CD4 as a primary receptor and CCR5 or CXCR4 as co-receptors • The receptor can determine cell-type specificity and host range (other factors such as a post-entry block may also play a role)

Question 228

Attachment of enveloped viruses

Answer 228

* Viralglycoproteinsarepresentintheviralenvelope * Glycoproteinsinteractwithcellularreceptorstoattach * Sometimesalsouseco-receptorsegHIV

Question 229

Attachment of non-enveloped viruses

Answer 229

e.g. adenovirus, no envelope | polio bind to receptor

Question 230

Entry into cells

Answer 230

Can happen in 2 ways – Fusion of virus envelope with cellular membrane – Receptor mediated endocytosis, generally for non-enveloped viruses

Question 231

fusin for entry

Answer 231

e.g. herpesvirus entry

Question 232

Endocytosis

Answer 232

* Endocytosis is a fundamental process by which macromolecules are taken into cells * After attachment all non-enveloped viruses (and some enveloped viruses) are taken up by endocytosis * Release of the viral genome is dependent on conformational changes in viral proteins triggered by receptor binding or the low pH of the vesicle * Enveloped viruses which are endocytosed can utilise fusion to cross the vesicle barrier

Question 233

Virus life-cycle

Answer 233

``` 1.Attachment and entry to host cell • Receptors • Membrane fusion • Endocytosis 2. Uncoating 3.mRNA synthesis- production of viral proteins 4.Replication of the viral genome 5.Assembly of new virions and release ```

Question 234

uncoating

Answer 234

• Uncoating: release of viral genome from the capsid • Generally poorly understood process • Uncoating can occur at: HIV uncoating at – the plasma membrane – within endosomes – the nuclear membrane

Question 235

biosynthesis

Answer 235

• mRNA synthesis- production of viral proteins • Replication of the viral genome

Question 236

Biosynthesis

Answer 236

* GenerationofmRNA * TranslationofmRNAintoviralproteins * Replicationofthegenome * Hostcellribosomesareusedfortranslationof mRNA; therefore the virus must make mRNA which can be read and translated by host ribosomes

Question 237

Central dogma of molecular biology

Answer 237

DNA->RNA ->Protein

Question 238

DNA viruses

Answer 238

Most DNA viruses must get their DNA genome into the nucleus as they use cellular DNA dependent RNA polymerase to produce viral mRNAs Exception: poxviruses-brings their own DNA dependent RNA polymerase as it replicates in the cytoplasm and cellular DNA dependent RNA polymerase is found in the nucleus Advantage of DNA over RNA is increased replication fidelity (accuracy), however this also means that DNA viruses are slower to evolve and adapt than RNA viruses

Question 239

ss DNA e.g. parvovirus

Answer 239

ss DNA → ds DNA → mRNA → translation • dsDNAmustbemadefrom ssDNA before mRNA is made • ssDNAconvertedtodsDNA by cellular enzymes • CellularDNA-dependent polymerase need to replicate viral genome

Question 240

special viral proteins

Answer 240

tools of trade replication primary aim of all virus is to produce mRNA and to replicate their genome if you r a DNA virus then generally you need rely on the host machineryto do this for u however most RNA viruses are more independent

Question 241

special viral proteins : RNA polymerases

Answer 241

During our own replication cycle we can copy DNA to DNA using a number of different DNA-dependent DNA polymerases (DdDp). We can also transcribe DNA-> mRNA (DNA-dependent RNA polymerase) However we cannot: copy RNA->RNA Therefore all RNA viruses (positive and negative sense) must encode for their own RNA-dependent RNA-polymerases (RdRp)

Question 242

RNA pol

Answer 242

For negative sense viruses, such as Influenza virus this RdRp must be carried in with the virus particle i.e. it is a structural component of the virion It needs to do this to first copy it’s negative sense genome into mRNA

Question 243

ds DNA herpesviruses

Answer 243

ds DNA → mRNA → translation

Question 244

ss(-) RNA

Answer 244

Eg: Orthomyxoviridae (influenza) • Encodes an RNA-dependent RNA polymerase, which is a virion component • ss(-) RNA is transcribed by viral RNA-dependent RNA polymerase into (+) mRNA • ss (+) RNA generated serves as a template to make new ss(-) virion RNA or to make proteins

Question 245

dsDNA with reverse transcription

Answer 245

* Includes Hepatitis B virus * partially double stranded DNA * Cellular DNA-dependent RNA polymerase generates mRNA * mRNA codes for proteins * mRNA also reverse transcribed to DNA (brings in its own reverse transcriptase in the virion) * Cellular DNA polymerase generates dsDNA

Question 246

Assembly

Answer 246

Assembly • Virus assembly occurs spontaneously within the infected cell • Highly ordered process • Proteins and nucleic acids brought together – Self assembly – Assembly using virus encoded proteins • Not all viral proteins will necessarily be in the virion

Question 247

1. Release via cell lysis

Answer 247

1. Release via cell lysis • Infections with many viruses results in cell death and destruction • Structural integrity of the cell is damaged • Poliovirus can induce cell lysis within approximately 8 hrs of infection

Question 248

2. Budding from the host membrane

Answer 248

2. Budding from the host membrane } Viral glycoproteins become embedded in host cell membrane } Other viral structural proteins and viral genome assemble at plasma membrane } Viral particle bud from the cell } Influenza requires neuraminidase (NA) to release it from host cell

Question 249

3. The secretory pathway

Answer 249

3. The secretory pathway • The secretory pathway is used by the cell to release proteins outside the cell • Consists of a series of steps from the ER and golgi to a vesicle which fuses with the plasma membrane

Question 250

exit via the secretory pathway e.g. hepatitis C

Answer 250

* Somevirusesusethis pathway for egress | * Allowsviralglycoproteinsto accumulate at intracellular membranes rather than at cell surface

Question 251

cell to cell transmission e.g. HIV

Answer 251

* Some viruses can spread directly from one cell to another neighbouring cell (eg VZV) * May cause fusion of infected cell with multiple uninfected cells- syncytia

Question 252

how to stop a virus infection by targeting the replication cycle

Answer 252

``` • Target steps which are unique to virus lifecycle • Prevent attachment and entry – Neutralising antibodies – Receptor analogues (acts like cellular receptor) – Fusion inhibitors • Prevent biosynthesis – Inhibit viral polymerases – Viral RNA replication – Reverse transcriptase inhibitors-HIV • Prevent assembly – Protease inhibitors – Prevent capsid assembly • Prevent release – Neuraminidase inhibitors-influenza ```

Question 253

Virusesentercellviaspecificreceptorswhichdefinehost range and tissue tropism • Replicationinvolvesbothvirus-encodedandhost- encoded factors • Pathwaysforsynthesisofprogenygenomedependson nucleic acid type and configuration • Virusreplicationcycleoffersbothimmunologicaland antiviral drug targets

Answer 253

T

Question 254

Viral pathogenesis-

Answer 254

important definitions Pathogenicity [Gr. "pathos", pain]: ability to cause disease Pathogen: organism able to cause disease Pathogenesis: means by which organism produces disease in the host A result of: • injury to discrete populations of cells • in particular target organs • producing signs & symptoms of disease in a given host Virulence: “capacity” to produce disease

Question 255

Pathogenicity

Answer 255

Pathogenicity [Gr. "pathos", pain]: ability to cause disease

Question 256

Pathogen:

Answer 256

Pathogen: organism able to cause disease

Question 257

Pathogenesis

Answer 257

Pathogenesis: means by which organism produces disease in the host A result of: • injury to discrete populations of cells • in particular target organs • producing signs & symptoms of disease in a given host

Question 258

Virulence:

Answer 258

“capacity” to produce disease

Question 259

Key requirements for a virus to establish a successful infection

Answer 259

• Find a way to enter the host - viral entry • Find a way to get through the host defenses - immune responses • Move through the host - dissemination/spread To spread infection, viruses must: • Find a way for new viral progeny to exit infected cells and host - transmission

Question 260

Viral infection

Answer 260

``` Viral infection • Routes of virus entry into host • Spread of virus within host • Immune response • Types of infections • Spread to others - shedding, transmission • Fate of host ```

Question 261

portal of entry

Answer 261

* skin | * respiratory tract • gastrointes0nal tract • genitourinary tract • conjunc0va

Question 262

routes of virus entry skin

Answer 262

Skin may be penetrated by viruses as a result of: -­‐ mechanical trauma/injec0on (HPV,HIV, HSV, HBV) -­‐ by the bite of an infected mosquito (arboviruses) -­‐ by the bite of an infected animal (rabies) Viruses o?en do not mul0ply locally but are carried away from site of infec0on: by bloodstream (HBV, arboviruses) or migration along nerves (rabies)

Question 263

route of virus entry respiratory tract

Answer 263

• Major route of invasion: 1) For viruses causing local respiratory infection Eg. RSV, influenza, rhinoviruses • Inhalation of viruses as aerosolised droplets – Coughing, sneezing 2) Other viruses causing asymptomatic initial infection then generalised spread Eg. Chickenpox (VZV), Measles, mumps • Host physical defenses – Mucus lining and ciliated cells – Alveolar macrophages

Question 264

routed of virus entry GIT

Answer 264

Eating, drinking, common route, faecal-oral Systemic infection; enteroviruses, hepatitis A, poliovirus Localised infection; rotavirus, norovirus Hostile environment Virus survival depends on stability against the following Physical host defenses: – Stomach - acidic – Intestine - alkaline – Digestive enzymes – Bile detergents – Mucous lining the epithelium

Question 265

Routes of virus entry: Genitourinary tract

Answer 265

• Infection via sexual activity – through tears/abrasions in lining - HIV – infect epithelium - Papillomaviruses (local lesions) – infect underlying tissues • Sensory neurons - HSV • Lymphoid tissue -HIV • Host defenses – Low pH (vagina) – Mucous layer, macrophages

Question 266

Routes of virus entry: Conjunctiva

Answer 266

* Abrasion,poorsanitation * localisedinfections-conjunctivitis * SpreadtoothersitesegHSV-1spreadtoneurons • Hostphysicalbarriers;tears,mucous,proteases

Question 267

Types of viral infection

Answer 267

Types of viral infection Localised infection – Replication at primary site of infection – Spread to adjacent cells Disseminated infection* – Must breech physical and immunological barriers – Extends beyond primary site of infection Systemic infection* – Many organs affected *Viruses need to move to target organ/tissue or preferred site of replication

Question 268

Systemic infection*

Answer 268

Systemic infection* – Many organs affected *Viruses need to move to target organ/tissue or preferred site of replication

Question 269

Localised virus infection

Answer 269

• Manyvirusesmultiplyinepithelialcellsatsiteofentry – produce a spreading infection – then shed directly to exterior • Respiratory infections – Influenza, rhinoviruses • Gastrointestinal infections- Rotaviruses • Skin infections- Papillomaviruses

Question 270

disseminated virus infection

Answer 270

``` • Via circulatory system • organ invasion from virus migrating from blood vessels • directly through capillaries via bite or puncture • HIV - T lymphocytes, monocytes • EBV - B lymphocytes • Measles – monocytes • VZV- T lymphocytes ```

Question 271

Viral dissemination | Via nervous system

Answer 271

``` Enter sensory or motor nerve ending • Sensory - dorsal root ganglia • Motor - motor neurons Eg. rabies, poliovirus HSV, VZVViral dissemination Via nervous system Enter sensory or motor nerve ending • Sensory - dorsal root ganglia • Motor - motor neurons Eg. rabies, poliovirus HSV, VZV ```

Question 272

innate immunity

Answer 272

``` First line of defense • Skin • Mucous membranes • Gastric juice • Normal bodyflora Passive barriers, immediately effec2ve Second line of defense • Natural killer cells • (Macrophages) • (Eosinophils) • Cytokines (e.g. interferons) • Fever Ac2va2on required, Effec2ve in less than 24 h ```

Question 273

adaptive immunity

Answer 273

``` Third line of defense • T-­‐cells (cell killing, cytokines) • B-­‐cells (an.body produc.on) Effec2ve after a few days ```

Question 274

different types of infection e.g. influenza virus

Answer 274

* Rapid production of infectious virions * Rapid resolution and elimination of infection * Typical course for viruses such as rhinovirus, rotavirus, influenza virus * Infections usually brief in immunocompetent hosts * Virions and infected cells are completely cleared by the immune response

Question 275

different tyoes of infections 2. persistent infection e.g. lymphocytic choriomeningitis virus for slow virus infection e.g.HIV

Answer 275

• • Unlike acute infection, persistent infection is not cleared effectively by the immune response Virus particles or products continue to be produced for long periods Two types of persistent infection (i) slow/chronic and (ii) latent (i) Slow/chronic Virions produced throughout although symptoms may only appear late (eg lymphocytic choriomeningitis virus) Alternatively, long periods of time with low virus production (eg HIV) or infectious genome spread (Measles sub acute sclerosing panencephalitis)

Question 276

persistent infection LATENT

Answer 276

• After initial acute infection, infectious virus is completely cleared by the immune response • Viral genome persists without any detectable infectious virus production • Periodically virus can “re-awaken” from latency by a process called reactivation • Reactivation leads to new infectious virus with/without disease • Herpesviruses characterised by their capacity to establish latent infection

Question 277

Viral shedding: Release of infectious virus from host Transmission via aerosols

Answer 277

``` Some of the most medically important viruses are spread via aerosol droplets (sneezing and coughing) Examples: - Influenza virus - SARS coronavirus - rhinovirus - adenovirus ```

Question 278

Viral shedding | Faecal-Oral Transmission

Answer 278

• Mostviralgastroenteritisoccursinplaceswherehumancongregationtakes place in confined places Eg: school, daycares, cruise ships, restaurants and summer camps • Thereisusuallyanexceptionallyhighamountofvirusshedinthewatery diarrhoea and vomiting associated with viral gastroenteritis • However,becauseofthereasonthatthesevirusesareextremelycontagious in nature, they are also spread through other routes: - Shellfish – when harvested in contaminated sewage waters - When people have contact with objects or surfaces which are contaminated - Through infected people who may be preparing foods for others. - When water used is contaminated with sewage • Viruses spread via the fecal-oral route include: poliovirusHep A and Hep E, rotavirus and norovirus

Question 279

Viral shedding | Transmission via blood and body fluids

Answer 279

sViral shedding Transmission via blood and body fluids • Blood- West Nile Virus, dengue virus, hepatitis C, HIV • Blood transmission via biting insects, sexual activity, childbirth, exposure to contaminated blood • Semen- HIV, CMV, hepatitis B • Breast Milk- CMV • Urine- hantaviruses

Question 280

Transmission of viral disease exam

Answer 280

Successful Transmission depends on... 1) number of viruses shed - more is better 2) stability of virus in environment – those resistant to desiccation better survival rates, most viruses are unstable on prolonged drying 3) number of virus particles required to infect a new host - dependent on virus and route of transmission

Question 281

Routes of Transmission

Answer 281

Routes of Transmission • Horizontal transmission • Vertical transmission • Zoonoses

Question 282

Transmission between humans | Horizontal

Answer 282

– Respiratory tract, cough, sneeze and saliva, blood – Faecal-oral – Sexual contact

Question 283

Vertical Transmission | mother to child

Answer 283

• Prenatal - transplacental – HIV, rubella, CMV • Perinatal - infected birth canal – Hepatitis B – HSV • Postnatal - milk or direct contact – CMV, Hepatitis B

Question 284

Zoonoses - Transmission from animals

Answer 284

Biting arthropods (e.g.dengue virus) or vertebrate reservoirs (rabies virus)

Question 285

What causes the symptoms?

Answer 285

1) Damage to cells due to virus replication: - cell death by rupture of cell during virus release - cell commits suicide in response to infection (apoptosis) - infected cell loses function - infected cell transformed by virus – tumours

Question 286

What causes the symptoms?

Answer 286

2) Damage due to the host response to infection: - Immunopathology - antibodies, and immune cells destroy infected cells - tissue damage - Inflammation - Symptoms of immune cells infiltrating the area where virus infection has occurred (swelling, rash etc.)

Question 287

What does “Epidemiology” mean?

Answer 287

• Epidemiology is the study of health-­‐event paSerns in a society • It is the cornerstone method of public health research • Viral epidemiology uses informa;on about: -­‐ the virus and the host -­‐ behavioural and environmental factors • Helps to determine the risk of disease in the human popula;on • Helps to determine op;mal treatment approaches to clinical prac;ce and for preven;ve medicine.

Question 288

Viral Epidemiology – The Virus

Answer 288

• Disease syndrome Eg fever, encephali;s, lesions, respiratory • Virulence Eg subclinical, mild, severe, fatal • Gene;c and an;genic varia;on Eg Influenza • Transmissibility Eg Highly infec;ous (cold flu), poorly infec;ous (rabies, HIV)

Question 289

Viral Epidemiology – The Host

Answer 289

Innate immunity -­‐ Ability to ac;vate interferon, NK cells Acquired immunity -­‐ Ability to produce an;bodies and virus specific T cells Popula;on -­‐ size and dynamics (density, movement) Eg Acute viral infec;ons (measles, mumps etc.) requires large dynamic popula;on Eg chronic infec;ons (HCMV, EBV, HIV, HPV) can survive in small isolated pops

Question 290

Viral Epidemiology – Environmental factors

Answer 290

``` Climate -­‐ seasonality Vector/reservoir host breeding -­‐ interac;ons with suscep;ble individuals -­‐ standing water Virus survival -­‐ humidity and temperature Geography -­‐ eg. physical isola;on or open borders ```

Question 291

Viral Epidemiology – Behavioural factors

Answer 291

``` Socio-­‐economic -­‐ living condi;ons, water supply Personal hygiene -­‐ hand washing, food prepara;on Travel habits -­‐ increase in rapid air travel and tourism (eg SARS-­‐coronavirus) Safe sex prac;ces -­‐ condoms, health checks ```

Question 292

Prevalence

Answer 292

- ­‐ number of cases at a point in ;me (chronic illness) - ­‐ expressed as the propor;on of the popula;on who have the infec;on/disease at a given point in ;me eg. Prevalence of HIV infec;on in Australia in 2004 was 0.07% of popula;on

Question 293

Incidence

Answer 293

Incidence - ­‐ frequency of new cases over ;me (acute illness) eg. approx 1.1 new cases of dengue per 100,000 popula;on were no;fied in Australia 2002

Question 294

pandemic

Answer 294

Pandemic -­‐widespreadepidemic ie. spread of human disease across a large geographical region (eg across borders, con;nents) Epidemics and pandemics result from outbreaks of disease

Question 295

epidemics

Answer 295

Epidemic -­‐peak in disease incidence in a given human popula;on, and during a given period, that substan;ally exceeds endemic baseline ie. occurrence in a community or regions of cases of disease clearly in excess of normal expectancy

Question 296

endemics

Answer 296

Endemic -­‐con;nuous occurrence of disease

Question 297

The NaConal NoCfiable Diseases Surveillance System

Answer 297

• NNDSS established in 1990 • Co-ordinates the national surveillance of an agreed list of communicable diseases or disease groups in Australia • Provides a means of detecting/monitoring outbreaks of disease, epidemics/pandemics • Data sent electronically from states and territories daily or several times a week. Published by the Dept Health and Aging • 65 notifiable diseases (~ 27 are diseases caused by viruses)

Question 298

whats outbreak

Answer 298

Disease with greater than expected morbidity or mortality • Increase of cases above background – background determined by surveillance data

Question 299

index case

Answer 299

* Index case (also called patient “zero”): the first patient that indicates the existence of an outbreak * The index case may indicate the source of the disease, the possible spread, and what reservoir holds the disease in between outbreaks

Question 300

Epidemiological invesCgaCon

Answer 300

Epidemiological invesCgaCon • Confirm outbreak – Real or artifactual increase above background? • Bettertestingfordiseasemayresultinartificialincrease • Confirm diagnosis – Consistent with clinical features and history – Laboratory confirmation (where possible) • Environmental investigation – Samples (eg food, water, animals, surface swabs) – Interview relevant staff – Policies and procedures • Patient data – Demographics – Onset and symptoms – Exposure to known risk factors of disease

Question 301

Outbreak Control Measures

Answer 301

Outbreak Control Measures • Prophylaxis • Vaccina;on (target at risk groups) • Transmission control (eradicate vectors, quaran;ne, improved hygiene/sexual prac;ces)

Question 302

communication

Answer 302

• Outbreak communication – Publish, meetings with stakeholders, industry etc. • Outbreak documentation – Especially if new source of infection is identified – Lessons learned – improve investigation methods for the future

Question 303

norovirus

Answer 303

• Genus Norovirus, Family Caliciviridae • Single-­‐stranded (+) RNA, non-­‐enveloped viruses that cause acute gastroenteri;s in humans • responsible for 5-­‐10% of serious gastroenteri;s cases

Question 304

norovirus clinical features

Answer 304

* Adults and Children | * Usual incuba;on period is

Question 305

virus outbreak investigation

Answer 305

``` Norovirus outbreak: wedding cake Epidemiological investigation 1. survey 2. same symptoms and time 3. risk factors for developing illeness p less than 0.001 4. environmental investigation 5. laboratory investigation - stool sample ```

Question 306

Inflammation includes...

Answer 306

* A tissue-based reaction * Pain * Coagulation * Destruction of microbes and host cells * Healing of tissues

Question 307

But, if blockade ...inflammation

Answer 307

infiltration of tissues (granulomas, etc.) particular forms (pannus, etc.) distortion of tissues (fibrosis, etc.) (chronic) DNA oxidised->neoplasias

Question 308

Summary: body’s defence against micro-organisms

Answer 308

1. Barriers: outer covering of body – skin and mucous membranes (e.g. mouth, gastrointestinal tract), and secretions (mucous, tears) 2. “INNATE IMMUNITY” (OR “Innate anti-microbial response”): inflammatory phagocytes (neutrophils and macrophages) plus plasma proteins (e.g. complement system), and Natural Killer (NK) cells 3. Lymphatic system: drainage to lymph nodes – more phagocytes encountered 4. “ACQUIRED IMMUNITY” (or “Adaptive immunity”): humoral (antibody-mediated) and cellular (leucocyte-mediated) immunity

Question 309

thrombosis

Answer 309

1. injury exposes collagen 2. blood patelets attach tocollagen, forming initial haemostatic plug 3. release of thromboxane A2and ADP from platelet 4. activation of thrombin, formation of fibrin 5. Aggregation of platelets, deposition of thrombin and stabilisation of initial plug to form “thrombus”.

Question 310

what is definition of inflammation?

Answer 310

inflammation is the rxn of VASCULARISED tissues to LOCAL injury or infection, characterised by the MOVEMENT OF FLUID and LEUCOCYTES out of the blood into the extravascular tissue

Question 311

what are the roles of inflammatory response?

Answer 311

1. to localise micro-organisms | 2. to eliminate micro-organisms, damaged cells, inanimate foreign particles, or antigens

Question 312

2. Chronic inflammation

Answer 312

2. Chronic inflammation • • Adelayed,prolongedresponsetoinjuryorinfection, taking two major forms: characterised by the presence in the affected tissue of many macrophages and lymphocytes (chronic granulomatous inflammation) • • characterised by the presence of large numbers of neutrophils (chronic suppurative inflammation) Note:Continuousdestructionandrepairofnormal tissue are always seen in chronic inflammation.

Question 313

types of leukocytes involved

Answer 313

* Acute = polynuclear | * Chronic = mononuclear

Question 314

what is characterised for chronic granulomatous inflammation? e.g. TB

Answer 314

- characterised by the presence in the affected tissue of many macrophages and lymphocytes giant cells

Question 315

what is characterised for chronic suppurative inflammation ? eg.chronic abscess

Answer 315

charaterised by the presence of large number of neutrophils. and some macrophages rare

Question 316

importance of inflammation

Answer 316

1. Positive roles in promoting host survival Direct role in host defence against micro- organisms. Role in initiating adaptive immune response. Role in initiating tissue healing mechanisms. 2. Deleterious effects on host survival (complications of inflammation) Acute inflammation: • appendicitis (possibility of perforation) • meningitis (intra-cranial pressure) Chronic inflammation: • tuberculosis (impairment of lung function) • arthritis (incapacitation) • initiation of cancer?

Question 317

what causes CELSUS

Answer 317

1. RUBOR (redness) caused by vasodilation 2. CALOR(heat) caused by vasodilation 3. TUMOR (swelling) caused by increase vascular permeability and increased granulation tissue 4. DOLOR (pain) caused by physical and chemical stimulation of nociceptors + FUNCTIO LAESA (lost/altered function) caused by pain, reflex muscle inhibition, disruption of tissue structure, fibroplasia and metaplasia

Question 318

what accompanying the fluid movement (exudate)

Answer 318

1. inflammatory stimulus 2. increase permeability 3. increase transudation 4. exudation

Question 319

major forces at vessel wall

Answer 319

going out is the hydrostatic force P, | going inside the vessel is osmotic P (pi)

Question 320

microcirculation

Answer 320

• blood vessels smaller than 100 μm (i.e. arterioles, capillaries, and venules).

Question 321

exudation

Answer 321

Following the initial hyperaemia, fluid (containing plasma proteins) moves from the blood into the affected tissue. This fluid movement leads to slowing of the blood flow in the affected area. The vessels appear “congested”. (Example follows). Swelling results from the increased fluid content of the tissue. Accompanying the fluid movement is emigration of neutrophils from the blood into the affected tissue.

Question 322

``` • Normal conditions: – Membranes are impermeable to proteins (dots) – Filtration = reasborption • Inflammation: – Gaps – Proteins escape – Result: inflammatory oedema!  ```

Answer 322

T

Question 323

oedema

Answer 323

accumulation of fluid extra-vascularly in tissues

Question 324

PURULENT: adjective from “PUS” SUPPURATION: formation of PUS

Answer 324

T

Question 325

How exudation?

Answer 325

In mild acute inflammation: Through inter-endothelial gaps in post-capillary venules only. In more severe inflammation: Resulting from damage to endothelial cells in all micro-vessels.

Question 326

Contraction of endothelial cells! | 

Answer 326

Carbon particles leave the vascular lumen and | enter in perivascular spaces

Question 327

The increase in permeability is limited to post-capillary venules !

Answer 327

T

Question 328

Why exudation?

Answer 328

``` Fluid: • dilution of toxins • increased flow into lymphatics Plasma proteins: • antibody • complement system components • fibrin system components Neutrophils: • destruction of micro-organisms ```

Question 329

Sources of mediators of vascular permeability changes

Answer 329

1. amines from mast cells and platelets 2. lipid-derived from leucocyte and parenchyma 3. plasma derived from plasma protein precursors

Question 330

histamine

Answer 330

Source: • mast cells, platelets Activities: • vasodilation (all microvessels, but primary action on arterioles) • increased vascular permeability (post-capillary venules only)

Question 331

what does vasodilation apply to

Answer 331

arterioles

Question 332

vasodilation mediators

Answer 332

histamne, kenins, PG E2, PG I2

Question 333

what does Increased vascular permeability apply to

Answer 333

post-capillary venules

Question 334

increase vascular permeability mediators

Answer 334

histamine | kenins, C3a, C5a and Leukoreienes B4 and C4

Question 335

injury and pain

Answer 335

``` injury cause: 1.release of PG and other mediators 2. platelet aggregation 3. mstocyte degranulation 4. activation of immuno-competent cells these all lead to the stimulation of nociceptive nerve endings ```

Question 336

pain sensitisation

Answer 336

Sensitisation of pain receptors by prostaglandins

Question 337

The 2 major components of inflammation

Answer 337

• VASCULARcomponent – Oedema – Mediators (U4L11) • CELLULARcomponent – Platelets – Leucocytes

Question 338

what are the neutrophil events in acute inflammation

Answer 338

1. neutrophil margination in small vessels 2. emigration from vessel into tissue 3. chemotaxin release and chemostatic response 4. phagocytosis of micro-organism 5. killling of micro-organism 6. death of neutrophil

Question 339

Neutrophil adherence to endothelium

Answer 339

• Stage 1: “activation” • Stage 2 “rolling” – mediatedbyproteinscalled selectins,newly expressed on the endothelium. • Stage 3: “adhesion” – mediatedby integrin proteins,constitutively expressed on the neutrophil, binding to receptors on the endothelium. • Stage 4: “emigration” – also mediated by integrins

Question 340

Phagocytosis & Degranulation

Answer 340

• Phagocytosis (“to eat and destroy”) – Attach – Engulf – Kill • Degranulation and the oxidative burst destroy the engulfed particle

Question 341

Chemotactic factors include:

Answer 341

* Complement components * Arachidonic Acid (AA) metabolites • Soluble bacterial products * Chemokines

Question 342

Neutrophil movement is influenced by chemicals

Answer 342

CHEMOKINESIS: increased movement in random directions. CHEMOTAXIS: increased unidirectional movement, towards the source of the signal. TISSUE ACCUMULATION: nett increase in neutrophils in an anatomical location. CHEMOTAXIN, CHEMOTACTIN, CHEMOATTRACTANT: agent that can induce chemotaxis in target cells.

Question 343

direct acting chemotactic on neutrophil

Answer 343

Leukotrienes Interleukin-8 Formylated peptides*

Question 344

indirect acting chemotactic on neutrophil

Answer 344

TNF, IL-1 and LPS “Indirect” agents act on other cells (e.g. macrophages) to induce release of chemotaxins (e.g. interleukin-8). Interleukin-8, interleukin-1 and tumour necrosis factor are “cytokines”.

Question 345

polarised neutrophil contain?

Answer 345

1. lamellipodium at the front 2. nucleus 3.granules and uropod is at the back

Question 346

polarised neutrophil contain?

Answer 346

1. lamellipodium at the front 2. nucleus 3.granules and uropod is at the back lacking ER and golgi and mitochondria, cant synthesis proteins, cant aerobic, rely on anaerobic environment

Question 347

killing of bacteria and fungi by neutrophil

Answer 347

1. phagocytosis of particles (forming a vacuole termed a phagosome) 2. fusion of cytosolic granules with phagosome forming phagolysosome 3a. release from granules into phagolysosome of antimicrobial proteins 3b. oxidative burst (formation of ROS) directed into phagolysosome 4. killing of microorganism

Question 348

Neutrophils never give up...

Answer 348

Neutrophils never give up... • As they die, neutrophils release “neutrophil extracellular traps (NETs)” • Made up of DNA strands with anti-microbial proteins attached • Trap and kill bacteria

Question 349

Formation of Neutrophil Extracellular Traps

Answer 349

1. nucleus break down 2. granule protein adhere to DNA strand 4. neutrophil lyses, NETs released, can trap bacterial

Question 350

Tissue accumulation of leukocytes in inflammation

Answer 350

• Early (minutes – hours):  maximum rate of migration of neutrophils. • Later (hours – days):  maximum rate of migration of monocytes. • Monocytes differentiate into macrophages.

Question 351

Structural and biochemical properties of macrophages

Answer 351

``` Structure • single-lobed nucleus • no obvious cytoplasmic granules • prominent endoplasmic reticulum and Golgi apparatus • abundant mitochondria Biochemistry • large protein synthesis capacity • energy from aerobic respiration or anaerobic glycolysis (glycogen) Consequences for function • long-lived cell • can differentiate and proliferate ```

Question 352

Cytokines is protein

Answer 352

Characteristics • Produced by a cell involved in an immune or inflammatory reaction • Modifies the activity of a different type of cell involved in that reaction • Stimulates or inhibits cellular functions

Question 353

Interleukin-1 (IL-1) and tumour necrosis factor (TNF) in inflammation

Answer 353

* Produced by several types of cell macrophages are major source * Broadly similar activities Often act synergistically Products of different genes Bind to different receptors * Over-production can contribute to tissue damage e.g. arthritis

Question 354

Synergistic systemic effects of IL-1 and TNF in inflammation

Answer 354

injury and infection cause macrophage to release TNF and IL-1 and send to 1. stem cells->leucocytes 2. endothelial cell: expression of adhesion molecules 3. T cell-> proliferation 4. hypothalamua-> fever

Question 355

Innate immune cell recognition of pathogens

Answer 355

• Identification of “non self” – Evolutionarily conserved microbial components or products (“pathogen-associated molecular patterns”, PAMPs) • Co-evolution of pattern recognition receptors (PRRs) – Toll-like receptor system – Several others

Question 356

Pattern recognition receptors: | an interface between the microbial world and immune system

Answer 356

T

Question 357

Pattern recognition receptors (PRRs): Roles

Answer 357

* Detect microbial infections | * Trigger anti-microbial host defences • Initiate adaptive immune responses

Question 358

Toll-like receptors recognise components of pathogens

Answer 358

e.g. TLR4 receptor recognise LPS

Question 359

Regeneration:

Answer 359

Regeneration: | replacement of injured tissue by parenchymal cells of the same type

Question 360

Repair:

Answer 360

replacement of injured tissue by fibrous tissue

Question 361

Healing:

Answer 361

regeneration, repair, or some combination of the two

Question 362

regeration definition

Answer 362

Regeneration: growth of cells and tissues to restore a lost structure – Amphibians: amputated limb – Mammals: liver after partial hepatectomy, cells of the haematopoietic system, epithelia of the skin and gastrointestinal tract Requires intact tissue scaffold Possible because cells have a high proliferative capacity and/or stem cells are present

Question 363

Repair by fibrosis: involves granulation tissue

Answer 363

1. Digestion of debris by macrophages: starts within 24 – 48 hours. 2. Proliferation of fibroblasts and ingrowth of new microvessels, starting around 48 hours. [Vessels are essential to provide nutrients for fibroblasts to synthesise collagen]. 3. Fibroblasts migrate into margins of wound. 4. Fibrosis (fibrous tissue production by fibroblasts – main component is collagen).

Question 364

healing definition

Answer 364

Healing: tissue response to a wound (skin), inflammatory processes in internal organs, cell necrosis in organs incapable of regeneration (myocardium) Combination of regeneration and scar formation (fibrous tissue) in variable proportions – superficial wound of epidermis: healing by regeneration only – deep wound with damage in the dermis: collagen scar

Question 365

Mechanisms of | Tissue Proliferation & Growth

Answer 365

Recruitment of quiescent cells into the cycle into G1 phase - Most important Shortening of cell-cycle time – less important

Question 366

Proliferative capacity of cells

Answer 366

Labile cells: • normally proliferate to replace cells that are continually being lost • examples: gut epithelium; bone marrow stem cells Stable cells: • do not normally proliferate but capable of doing so when required • examples: fibroblasts; endothelial cells; hepatocytes Permanent cells: • rarely proliferate • examples: CNS neurons; cardiac myocytes

Question 367

Which cells? Which mediators? for renewal

Answer 367

Which cells? Which mediators? • Vascular cells – Endothelial cells – Circulating cells • Cells of the connective tissue (C.T.) • Elements of the C.T. matrix

Question 368

FOUR stages of healing:

Answer 368

``` FOUR stages of healing: 1 – HAEMOSTASIS 2 – INFLAMMATION 3 - PROLIFERATION Granulation tissue (soft callus) Scar – Fibrosis (hard callus) 4 – REMODELLING Contraction Scar maturation / wound strength ```

Question 369

Cytokines: signals between cells

Answer 369

``` the stimulus cu=ause effector cell to release cytokines which act on target cel Examples: • Tumour necrosis factor (TNF) • Transforming growth factor (TGF) • Platelet-derived growth factor (PDGF) ```

Question 370

First intention for healing

Answer 370

incision wound become a scar, no granulation tissue

Question 371

second intension for healing

Answer 371

1. open would 2. granulation tissue 3. scar with collagen and fibroblast

Question 372

Major differences 1st and 2nd intension

Answer 372

Major differences • First intention: – Margins can attach – Margins are sutured – No infection • Second intention: – Margins not ready to attach – Infection – Margins are devitalised: bruised or necrotic

Question 373

Healing by first intention: closed aseptic wounds

Answer 373

* Haemostasis: within seconds to minutes • Inflammation: within minutes to hours * Scab formation * Migration of fixed cells: within 24 hours • Regeneration: 3 days * Early scarring: 7-10 days * Scar maturation: 1 month-2 years (very rare)

Question 374

Healing by first intention: the principal steps | 

Answer 374

1. platelet and fibrin 2. neutrophil and macrophages 3. fibroblasts 4. connection between newly formed vessels, efficient angiogenesis

Question 375

FOUR Stages of Healing:

Answer 375

2. haemostasis 2. inflammation 3.-proliferation Granulation tissue (soft callus)- fibrin Scar – Fibrosis (hard callus) 4 – REMODELLING Contraction Scar maturation / wound strength

Question 376

haemostasis

Answer 376

first priority STOP bleeding - arteriole: vasoconstriction - blood clt: platelet and fibrin

Question 377

Phase 1: Haemostasis

Answer 377

Phase 1: Haemostasis • Plateletplug • Chemo-attraction – PolyMorphoNuclear Neutrophils (PMNs) – Monocytes – Lymphocytes “chemoattraction”: attraction (of cells) by chemicals (mediators, such as cytokines, chemokines)

Question 378

Phase 1: Haemostasis

Answer 378

Platelet Aggregation and Activation : - PDGF: platelet-derived growth factor - TGF-B: transforming growth factor - IGF-1: insulin-like growth factor - EGF: epithelial growth factor - vWF: von Willebrand factor - also release serotonin, which causes vasodilation and increased vascular permeability

Question 379

inflammation

Answer 379

``` second priority WARD OFF BACTERIA - worst case scenario - recruitment of cells - scavenging of debris ```

Question 380

Phase 2: Inflammation

Answer 380

• Neutrophils : 6-48 h – Kill bacteria – Secrete cytokines to cause inflammation • Monocytes : 48-72 h – Attracted to wound by cytokines (eg TGF-B ) – Extravasate and turn into macrophages – Secrete more cytokines to initiate proliferative phase • Lymphocytes – Modulate extent of inflammation

Question 381

proliferation -Granulation tissue (soft callus) Scar – Fibrosis (hard callus)

Answer 381

- scab: a natural dressing | - new structures

Question 382

Phase 3: Proliferation

Answer 382

``` Begins day 2-3 after wounding Lasts 2-4 weeks • Angiogenesis • Fibroplasia • Epithelialisation ```

Question 383

angiogenesis

Answer 383

angio=vessel | genesis=development

Question 384

Phase 3: Proliferation

Answer 384

Angiogenesis - necessary to support a wound environment that can repair the injury • Stimulated by – macrophage-derived growth factors (FGF, TGF-α, TGF-B, TNF) – hypoxia, fibronectin and hyaluronic acid (found in the wound matrix) • Supplies oxygen and nutrients for fibroblast proliferation and production of wound matrix

Question 385

phase 3:proliferation

Answer 385

* Fibroblasts migrate into wound on the fibrin scaffold left behind from haemostatic process * Macrophage-derivedgrowthfactorsstimulateproliferationof fibroblasts (collagen synthesised at an accelerated rate)

Question 386

Phase 3: Proliferation

Answer 386

Epithelialisation • Cells in basal layer at wound edge flatten • De-differentiation • Pseudopodformation • Migrate across wound - integrin receptors in underlying extracellular matrix • Cells along margin divide to reform mature, multilayered epithelium • For surgical wounds: complete wound coverage in 24-48 hrs.

Question 387

Phase 3: Proliferation

Answer 387

Epithelialisation • Process compromised by: • Bacteria • Protein exudate from leaky capillaries • Necrotic debris • Delayed epithelialisation = prolonged & profound inflammatory process • Facilitated by clean moist wound

Question 388

phage 3 proliferation. all form granulation tissue cause by the following

Answer 388

``` • Macrophages – growth factors • Epithelial cells – Migrate to the sides of edges • Endothelial cells – Angiogenesis • Fibroblasts – Extra Cellular Matrix formation ```

Question 389

remodelling - Contraction - Scar maturation / wound strength

Answer 389

modulation of proteins:fibrin and collagen | transformation of cells:myofibroblasts

Question 390

phase 4: remodelling wound contraction, second wk of healing

Answer 390

* Fibroblasts transform into myofibroblasts, this is stimulated by TGF-B, PDGF. * Collagen synthesis and degradation is controlled by metalloproteinases (produced by macrophages, epidermal cells, endothelial cells and fibroblasts) * Wound gains about 20% strength by 3 weeks. A scar is only about 70% of normal skin.

Question 391

Phase 4: Remodelling

Answer 391

``` 1. Contracture of the wound – Contraction of fibrin – Myofibroblasts – Fibroblasts and collagen lattice 2. re-epithelialisation and 3. organisation that will lead to would strength ```

Question 392

Wound Kinetics

Answer 392

* 1 week –no change in the size of a wound * 3 weeks almost 20% tensile strength * A scar has only ~70% of strength of normal skin * Healing time is logarithmically related to wound size

Question 393

Factors affecting Healing:

Answer 393

``` Systemic  nutrition  vitamin def.  age  immune status  other diseases Local  necrosis  infection  apposition  blood supply  mobility  foreign body ```

Question 394

Complications of healing

Answer 394

• Infection – Surgery axiom: “the resistance of wounds to infection is proportional to their blood supply” – Leucocytes deprived of oxygen have an impaired respiratory burst • Foreignbodies • Metabolic disorders/ microvascular problems: diabetes • Keloids (hypertrophic scars)