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Infection & Immunity > Bacterial & Viral Pathogenesis > Flashcards

Bacterial & Viral Pathogenesis Flashcards

1
Q

Define epidemiology

A

Study of occurrence, distribution and control of diseases in populations

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2
Q

What are the basic stages of pathogenesis for microbial Disease

A
  • Entry into the body
  • attachment/adhesion to cells
  • infection/colonisation and growth
  • pathological alterations of host = symptoms
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3
Q

Name some non-specific virulence factors

A

Extracellular proteins
Polysaccharide capsule (protection)
Toxins - damage inducing substances

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4
Q

Give some examples of pathogenic extracellular proteins

A 
Hyaluronidase
Processes, Nucleases, Lipases etc.
Collagenase
Streptokinase
Coagulase
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5
Q

What is Glycocalyx

A

Glycoproteins and glycolic is covering that surrounds cell membrane of some bacteria

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6
Q

What are the 3 types of Toxin

A

Exotoxins
Endotoxins
Enterotoxins

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7
Q

What are the 3 types of exotoxins

A

Cytolytic, A-B and superantigen toxins

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8
Q

Describe the function of Cytolytic toxins

A

Lose host cells by enzymatically degrading cellular components

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9
Q

Describe the function of A-B toxins

A

Consist of two Covenanter bonded subunits, A(ctive) and B(inding). B subunit usually binds to cellular surface to allow transport of A through membrane to damage cell

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10
Q

Describe function of superantigen toxin

A

Stimulate large amounts of immune response cells that lead to massive inflammatory reactions

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11
Q

Describe enterotoxins

A

Exotoxins affecting host small intestine
- produced by food poisoning and intestinal pathogens, bacteria including staph, clostridium, bacillus, vibrio chlorae, E. coli, salmonella etc.

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12
Q

Describe endotoxins

A

Produces only by gram negative organisms

- located in the outer layer of cell envelope of lysed gram negative bacteria

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13
Q

Describe the effect of endotoxins

A
  • released when lysed
  • causes diarrhoea,rapid decrease in leukocyte and lymphocyte and platelet numbers, release of cytokines and systematic inflammation
  • haemorrhagic shock and tissue necrosis (after high doses of endotoxins)
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14
Q

What is bloat

A

Uncontrolled increase of body size due acc. Of gases in body as a result of pathology or death

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15
Q

What is putrefaction

A

The decomposition of proteins by putrefying (anaerobic) resulting in the formation of polyamines with putrid odour - putrescine

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16
Q

What is gnotobiology

A

raising mammals under germ-free environments, or conditions with controlled spectra and numbers of microorganisms

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17
Q

Reasons for gnotobiology

A

Use genetically modified model systems
Study establishment and maintenance of immune system
Provide new insights on aetiologies

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18
Q

Health and disease are two different states of the body, what is the word for health —> disease

A

Pathogenesis

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19
Q

Health and disease are two different states of the body, what is the word for disease —> health

A

Convalescence

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20
Q

Define pathogenesis

A

Set of mechanisms by which an etiological factor causes a disease

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21
Q

Define epidemiology

A

The study of occurrence, distribution and control of diseases in populations

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22
Q

What are the 3 types of human-microbe interactions

A

Parasitic: one organism lives and benefits at expense of other

Symbiotic: both organisms benefit from each other

Commensals (Maybe opportunistic): neither organism particularly benefits or suffers or one can benefit with no obvious harm to other

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23
Q

Define virulence

A

Extent of pathogenicity expressed by pathogens

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24
Q

Define pathogenicity

A

Ability of pathogens to cause disease

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25
Q

Define attenuation

A

Long cultivation of pathogens in culture

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26
Q

Define ID50

A

Infectious Dose 50%: number of pathogens cells needed to cause 50% of host cells to show signs of infection

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27
Q

Define LD50

A

Lethal Dose 50%: the number of pathogen cells needed to cause 50% of host cells to die

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28
Q

Define infection

A

The colonisation of host by a pathogen

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29
Q

Define incubation period

A

The time between infection and symptoms of disease

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30
Q

Define acute period

A

Height of disease with pronounced symptoms

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31
Q

define Decline period

A

Symptoms subside

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32
Q

define Convalescence period

A

Returning to normal

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33
Q

How are microbes like E. Coli aides during adhesion

A

They produce adhesins that bind to host receptors on specific sugars present in fimbriae and pili

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34
Q

What is sepsis

A

Viraemia
Bacteraemia
Parasitaemia

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35
Q

What is toxicity in terms of pathogenicity

A

Aiding disease by different toxins that inhibit or kill host cells

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36
Q

What is invasiveness in terms of pathogenicity

A

Growing in a tissue to such amounts of cells that inhibit host functions and cause disease (even in the absence of toxins)

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37
Q

The action of toxins can be:

A

Direct: causing lysis or apoptosis to cells
Indirect: triggering biological activities that harm the host systematically

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38
Q

What is the significance of a polysaccharide capsule in terms of virulence

A

It takes over 10,000 unencapsulated bacteria to kill a mouse but it the bacteria is encapsulated then it can take less than 10.

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39
Q

What is mycolic acid

A

Each material in cell walls of mycobacterium that can inhibit phagocytosis by antibiotics

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40
Q

True or false: exotoxins and enterotoxins are proteins

A

False: ENDOtoxins and Enterotoxins are

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41
Q

True or false: Exotoxins are lipopolysaccharides

A

True

42
Q

True or false: exotoxins are less potent than endotoxins

A

False, other way around

43
Q

Do bacteria secrete endo or exotoxins

A

Exotoxins

44
Q

What does Anthrax result in

A

Reduction of RNCs especially and and leads to destruction of surrounding tissue
- spores are highly resistant to physical and chemical agents

45
Q

What 3 toxins are the cause of anthrax development

A

Protective antigen: which mediates entry is the two other proteins, Oedema and Lethal factor) which are all encoded by a plasmid

46
Q

Describe the appearance of anthrax colonies

A

Gram positive, with characteristic squared ends and ellipsiidal central endospores (resistant to staining and refactor to light)

  • Large cells
  • older colonies have ground glass phenotyoe
47
Q

What does oedema factor (EF) do

A

Ca2+ and calmodulin dependant.

Increases cAMP —> upsets water homeostasis —> liquid accumulation

48
Q

What does lethal factor (LF) do

A

Inactivated MAPK kinase —> fall in cellular signalling —> impaired macrophage function —> distorted immune system

49
Q

What are the 3 main types of anthrax

A

Gastrointestinal
Inhalational
Cutaneous

50
Q

How quickly can death account after inhaling anthrax bacilli

A

Inhalation of spores will lead to haemorrhagic pneumonia and death within 24 hours after the flu like stage that lasts for 2-4 days

51
Q

Characteristics of Botulism

A

Flaccid paralysis of muscles and respiritory failure

  • caused by botulinum toxin of anaerobic bacterium Clostridium botulinum
  • usually through contaminated food
52
Q

Characteristics of Clostridium botulinum

A

Anaerobic organism, heterogenous group, spire forming

  • under anaerobic conditions, spores can germinate under salt
  • at least 7 antigenicallu distinct botulinum exist A - G.
  • Types A, B, E and F are associated with human botulism
53
Q

What is the most poisonous substance known

A

Botulinum toxin, 1 gram can kill 10 Million people

54
Q

Characteristics of infant botulism

A

Most common form associated with consumption of contaminated food (usually honey or corn syrup)
Flaccid paralysis and respiratory arrest can develop, with rare death.

55
Q

How is botulism diagnosed

A

Search for Clostridium bacteria

  • toxin bioassay works in mice, not in infant or wound botulism.
  • demonstrate toxin presence in serum or stool by injecting either into mice and searching for botulism
56
Q

How is botulism treated

A

Early diagnosed food borne and wound can be treated with horse derived antitoxin which blocks the action of toxin

  • removing contaminated food from gut
  • wounds should have bacteria surgically removed
  • NOT with antibiotics as they promote paralysis
57
Q

Characteristics of Diphtheria infection

A

Caused by corynebacterium diphtheriae

  • bacteria multiply on epithelial cells of pharynx and cause local damage
  • local inflammation with false membrane, sometimes bleeding
  • life threatening complication is respiratory obstruction, myocarditis, fever and exhaustion
58
Q

Characteristics of cutaneous diphtheria infection

A

Bacteria colonised skin and subcutaneous tissue, developed Papua’s evolves into bronco ulcer that doesn’t heal. The exotoxins May cause systemic disease

59
Q

Treatment and control of respiratory diphtheria infection

A
  • Early administration of antitoxin
  • Penicillin and erythromycin
  • Immunisation with toxoid vaccine is recommended in childhood with boosters ever decade
  • immunity determines by Schick test
60
Q

True or false: staph epididimis secretes coagulase

A

False: Steph coccus does

61
Q

Describe enterotoxins

A

Endotoxins that cause gastrointestinal distress when ingested. Cause massive secretion if fluid in SI lumen —> vomiting and nausea
- mostly superantigen that activate T cells —> prod cytokines and stim macrophages

62
Q

When toxic shock syndrom usually occur

A

After infection during surgery By toxic shock syndrome toxin-1 (TSST-1) which is released by growing cells of s aureus

63
Q

What is leukocidin

A

A protein (produced by staph aureus) that destroys leukocytes. The process cause pus prod in skin boils

64
Q

What do carotenoids of staph aureus do

A

Destroy phagocytes like macrophages

65
Q

Name some reasons for antibiotic resistance (of staph aureus)

A
  • plasmids as well as chromosomes provide resistance against aminoglycosides, penicillins and chloramphenicol
  • use of antibiotics causes natural selection against it
66
Q

What is the usual reason for MRSA being resistant

A

Due to a mobile element-derives chromosomal mecA gene encoding a Penicillin Binding Protein with altered (reduced) affinity to penicillin beta-lactam rings

67
Q

Characteristics of a carbuncle

A

Infection involves several adjacent hair follicles, central necrotic core forms large ulcer requiring antibiotics.

  • local invasion of staph aureus
  • outer layer of fibroblasts
68
Q

Characteristics of endotoxins

A
  • NOT located inside bacterial cell
  • NOT a protein
  • Lipopolysaccharide component in Outer leaflet of cell membrane
  • released from the outside of cell when lysed
  • consist of 3 subunits: Lipid A, a core polysaccharide and O-polysaccharide
69
Q

Describe the 3 subunits of Lipopolysaccharides

A

Lipid A: responsible for toxicity
Core polysaccharide
O-polysaccharide: makes complex soluble and immunogenic

70
Q

True or false: endotoxins are produced by gram negative bacteria only (with possible exceptions)

A

True

71
Q

True or false: exotoxins are bound to the outside of the bacteria cell

A

False: they are metabolic products secreted from inside the cell

72
Q

True or false: endotoxins are more heat resistant than exotoxins

A

True: stable up to 1 hour at autoclave temp (121 degrees)

Exotoxins up to 60 degrees

73
Q

Describe the effects on the host of an endotoxins

A

Fever, malaise, shock, blood coagulation

74
Q

Describe the variable effect of exotoxins on the host

A

Could be a neurotoxin, cytotoxic, enterotoxins

75
Q

True or false: exotoxins are fever inducing

A

False, endotoxins are

76
Q

What are some representative diseases of exotoxins

A 
Botulism
Diphtheria
Cholera
Plague
Tetanus
77
Q

What are some representative diseases of endotoxins

A

Typhoid fever
Endotoxic shock
Urinary tract infection

78
Q

True or false: endotoxins activate nearly every non specific defence mechanism

A

True

  • complement in alternative pathway
  • coagulation
  • inflammation
  • cytokines and macrophage release
  • B cells etc.
79
Q

Characteristics of a retrovirus

A

Virus containing RNA that use reverse transcriptase for its replication

80
Q

What family does HIV (human immunodeficiency virus) belong to

A

Retrovirus

81
Q

How does HIV interact with the immune system

A

Destroys it by releasing HIV particles infecting and killing white blood cells, particularly CD4 surface protein expressing cells

82
Q

Characteristics of HIV virions

A

Lipid Bilayer: apx. 72 viral envelope GP spikes
Core Proteins
- RT: Reverse Transcriptase
- MA (Matrix Protein P17) forms shell to inner side of membrane to ensure integrity of virion
- CA (Capsid Protein P24) assemble in hexameric rings to constitute to capsid
- NC (nucleocapsid protein or P7) is needed for RNA stability and nucleocapsid assembly
- Gp41 and Gp120 are needed to enter cell

83
Q

Outline HIV replication in a CD4 host cell

A
  • Entry of virion into cell
  • conversion of RNA to DNA by RT
  • Integration of viral DNA into host DNA by viral integrase
  • Activation of T-cells leads to transcription and translation of viral genome
  • assembly of new virions
84
Q

Common features of HIV patients

A 
WEight loss
Fatigue
Fevers
Weakness
Lower CD4 count
85
Q

Diagnosis of HIV

A 
Direct identification is hard as often integrated into host chromosome and could be kept as provirus for years.
Serological tests
- ELISA
- HIV Enzyme immunoassay
- Western blot
86
Q

True or false: presence of HIV antibody doesn’t necessarily mean patient is infected with HIV

A

True, just means they have been exposed to it

87
Q

Name some manifestations of HIV infection

A

Shingles: limited painful skin rash one one side of body with blisters
Disseminated herpes
Kaposi’s sarcoma: rare cancer of blood vessels AIDS associated

88
Q

Major routes of HIV infection

A
  • unprotected sexual inter course
  • intravenous drug abuse
  • blood transfusions, organ transplants, haemophilic therapy, tattooing, contaminated needles
  • mother to baby at birth, breastfeeding milk
89
Q

Treatment of HIV

A

No effective vaccine or cure for HIV or AIDS
Post exposure prophylactic is needed
HAART is a prescription medicine used

90
Q

Describe the HAART prescription drug

A

Cocktail of 3-4 antiviral drugs including inhibitors of RT, Protease inhibitors, Nucleotide analogues

91
Q

Characteristics of HAART

A

Stops HIV replication (coz they can’t develop multi-resistance to it)
Infected Cells can potentially live up to 60 years before they die

92
Q

Describe Enfuviritide (anti-HIV Drug)

A

Fusion inhibitor composed of a synthetic peptide chain that acts by binding to the Gp41 membrane protein of HIV

93
Q

Explain Kochs postulate

A
  • the suspected pathogenic organism should be present in ALL cases of disease and absent in healthy animals
  • suspected organism should be pure cultured
  • cells from pure culture should cause disease in healthy animal
  • organism should be reisolated and shown to be the same as the original
94
Q

Examples of some pathogens that can’t be cultured in a lab

A

Mycobacterium leprae

Tryponema pallidum

95
Q

True or false: some diseases aren’t virulent by them selves

A

True, some are caused by combinations of factors e.g. liver cancer can be a product of Hepatitis B and D

96
Q

What did the discovery of slide media for cultivation allow

A
  • basic studies on biology of individual species and strains
  • diagnostic purposes
  • gene cloning and vaccine making
  • Recognising emerging infectious diseases
97
Q

Name the portals of entry

A

Skin, placenta, conjunctiva and mucous membranes of the respiratory, GI, urinary and reproductive tracts
- parenteral route is through skin puncture

98
Q

Difference between vertical and horizontal spread of infection

A

Vertical is from generation to generation e.g. through gametes
Horizontal is from person to person e.g. airborne

99
Q

Name some pathogens that can cross the placenta

A

Toxoplasma gondii
Treponema pallidum
Lentivirus (HIV)
Rubivirus

100
Q

Characteristics of the epidemiological triangle

A 
Who what (when) where 
Host, Agent [virus, bacteria etc.], (Time), environment (blood etc.)

Infection & Immunity (17 decks)

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