Infectious Diseases Flashcards
1
Q
What are prions
A
Composed of modified host protein
Lack dna/rna
Cause spongiform encephalopathies eg creutzfeldt-jakob
Associated withneurodegrnerative disease
2
Q
Define viruses
A
Obligate intracellular organisms
Contain dna or rna with protein coat - capsid
May be surrounded by lipid bilayer - envelope
3
Q
Define bacteriophages or plasmids
A
Mobile genetic elements that encode bacterial virulence factors
Eg adhesions, toxins, antibiotic resistance
4
Q
Define chlamydiae, rickettsiae, mycoplasms
A
Similar to bacteria but lack certain cell structures or metabolic capabilities
Chalmydiae- cause genitourinary infections, conjunctivitis, resp
Rickettsiae - transmitted by insect vectors eg lice, ticks, Q fever
Mycoplasmas - bind to epithelia cells cause atypical pneumonia
5
Q
Define fungi
A
Have thick, chitin-containing cell walls
Cause superficial infections, abscesses, granulomas
In immunocompromised can be opportunistic
Eg pneumocystis carinii
6
Q
Define Protozoa
A
Single cell with a nucleus, pliable plasma membrane and complex cytoplasmic organelles
Eg TV
giardia - intestinal Protozoa
Plasmodium - blood borne
7
Q
Define helminths
A
Highly differentiated multicellular organisms with complex life cycles
Disease in proportion to number of infecting organisms
Roundworms, flatworms
8
Q
Define ectoparasites
A
Are arthropods eg lice, ticks
May be vectors for other pathogens
9
Q
Why are syphilis lesions infectious
A
They contain spirochetes
10
Q
Where does secondary syphilis occur
A
Palms and soles
11
Q
Where are syphilis lesions
A
On the genitalia, mucus membranes, palms and soles
Painless
12
Q
When does secondary syphilis occur
A
2-10 weeks post primary infection
13
Q
Regarding hepatitis B what does IgG represent
A
Represents life long immunity
Presents after acute infections after IgM and persists for life
14
Q
With regards to hepatitis B what does surface antigen HBsAg mean
A
Active infection
15
Q
With regards to Hepatitis B what does E antigen /HBeAg indicate
A
Marker of viral replication and implies high infectivity
16
Q
With regards to hepatitis B what does HBcAb indicate
A
Past or current infection
17
Q
What does HBsAb imply
A
Implies vaccination or past or current infection
18
Q
What do you test for hepatitis B
A
HBcAb - for previous infection
HBsAg - for active infection
If both positive do further testing for HBeAg and viral load
19
Q
3 examples of diseases commonly spread by ticks
A
Lyme disease, scrub typhus, Rocky Mountain spotted fever
20
Q
How is Q fever transmitted
A
Caused by coxiella burnettii
Found in cattle sheep goats
Inhalation of spore like small cell variant from contact with milk urine faeces mucus
21
Q
When are aschoff bodies classically seen
A
Rheumatic fever
They are nodules found in hearts
Result from inflammation in heart muscle
22
Q
Incubation period of hepatitis E
A
6 weeks
23
Q
How is hepatitis E transmitted
A
Enterically, water borne disease
24
Q
Hepatitis E mortality in pregnant women
A
20%
25
4 conditions caused by streptococcus
Tonsillitis
Scarlet fever
Impetigo
Rheumatic fever
26
Examples of staphylococcus infection
Food poisoning
Impetigo
Pneumonia
TSS
Tonsillitis
Endocarditis
Osteomyelitis
27
Examples of dna virsuses
Adenovirus
Hepatitis B
HSV
HPV
Mollisc virus
28
Example of RNA virus
HIV
29
Most common primary site of TB
Lower part of the upper lobe or upper part of lower lobe usually close to epleura
30
Where does secondary TB occur
Near the apocalyptic pleura
31
Examples of rna viruses
Echovirus
Coxsackie
Rhinovirus
Influenza
RSV
Mumps
Hepatitis A D C E
Dengue
Yellow fever
Rabies
HIV
32
Describe rickettsia infections
Rickettsial bacteria
Vector borne obligate intracellular organisms
Infect the vascular endothelial cells
Especially those of brain and lung
Have an endotoxin
33
Describe polio
A picornaviride RNA virus
Replicates in the anterior motor unit of the spinal cord or brain stem
Causes symptoms in 1% of infected people
Transmitted fecal oral route
34
3 inmate defends mechanisms to infection
1. Physical barriers - skin mucus membrane
2. Cells of immune system - phagocytes, NK
3. Adaptive - B and T cells
35
How do viruses enter host cells
Binding to host cell surface proteins eg HIV to CD4
Translocation into the cytosol
Replication via virus specific enzymes
36
How do viruses kill hosts
Inhibiting host cell dna, rna, or protein synthesis
Damaging the plasma membrane
Lysing cells
Inducing a host immune response to virus infected cells
37
How does bacteria injure host tissues
1. Deliver toxins/endtoxins
Endotoxin is lipopolysaccharide that induces fever via host cytokines - TNF, IL-1
2. Adhere to and enter host cells
Adhesions include filamentous Pili
38
What is TB caused by
Aerobic, non spore forming non motile bacillus
M. Tuberculosis
39
What colour does TB stain
Stains red with acid fast stains
40
What happens in primary tuberculosis
Inhaled mycobacteria enter endosomes of alveolar macrophages
Cause endosomal manipulation - preventing acidification, maturation arrest, ineffective phagolysosome formation
Proliferate in macrophages
Bactaraemia and seeding
41
What happens after 3 weeks of TB infection
T cell mediated immunity
CD4 Th1 cells secrete TNF gamma
This activates macrophages to kill intracellular mycobacteria
42
What type of hypersensitivity response is TB
Type IV
43
What forms after TB infection has T cell mediated response
The non specific inflammation becomes granulomatous
Forms epitheloid granulomas
Often with central creating necrosis
Residual calcified scar in lung parenchyma = ghon complex
44
When does secondary TB occur
Occurs in a previously sensitised host
Usually occurs after many years by reactivation or re exposure
Often with immunocompromised
45
What is the main cause of tissue damage in secondary TB
Granulomas that fail to control mycobacteria
Cavities formed by cesating granulomas may rupture into blood vessels causing Haematogenous spread
46
What causes disseminated TB
Haematogenous spread
47
What organs are effected by Haematogenous spread of TB
Adrenals kidney bone
48
What happens with miliary TB
Massive Haematogenous dissemination of bacilli with widespread minute granulomatous foci
Especially in liver spleen marrow kidneys
49
What is staph. Aureus
Pyogenic gram positive coccus
50
What does staph. Aureus cause
Myriad of skin lesions, abscess, sepsis, osteomyelitis, pneumonia, endocarditis, food poisoning, TSS
51
How does staph aureus cause skin infections
Has a lipase that degrades lipids on the skin surface and then can cause skin infections
52
How does staph aureus attach to artificial material
A polysaccharide capsule that allows attachment to artificial material
Such as prosthetic heart valves, catheters
Resists artificial host cell phagocytosis
53
How does staph aureus cause food poisoning
Has enterotoxins which are exotoxins produced causing food poisoning in humans
54
Staph or strep more common for tonsillitis
Strep more commonly causes tonsillitis
55
With hepatitis B when does HBsAG appear
Before the onset of symptoms
56
With hepatitis B when does IgG appear
After acute infections
Persists for life
Represents life long immunity
57
With hepatitis B when does anti Hbe detectable
Only after disappearance of HBeAg
Implying acute infection has peaked
58
In hepatitis B what percentage are sub clinical
65%
These all will recover
59
In hepatitis B what percentage develop acute hepatitis
25%
60
In hepatitis B what percentage will develop chronic hepatitis
5-10%
61
Main route of transmission of hepatitis c
Inoculations and blood transfusions
62
High risk groups for hepatitis C
IVDU - 50-90%
Homosexuals
Haemodialysis
Haemophiliacs
63
Which has higher rate of progression to chronic disease hepatitis B or C
Hepatitis C
Over 50%
64
What is clostridium
Gram positive spore producing bacteria
Grow in anaerobic conditions
65
What does c. Tetani produce
Tetanospasmin
A potent neurotoxin causing muscle spasm
66
What does c.botulinum produce
A neurotoxin which blocks synaptic release of acetylcholine
67
What does c. Perfringens cause
Wound infections 1-3 days after injury
68
What is bacterial endotoxin
A lipopolysaccharide that is a structural component in the outer cell wall of a gram negative bacterium
69
How does bacterial endotoxin play a role in septic shock, ARDS and DIC
Through induction of excessive levels of cytokines such as TNF and IL-1
70
With regards to bacterial infectious gastroenteritis 3 ways and examples of how bacteria causes infection
1. Ingestion of performed toxin eg s.aureus, cholerae
2. Infection of toxigenic organisms that grow in the gut lumen and produce an enterotoxin eg e.coli
3. Infection by enteroinvasive organisms which destroy mucosal epithelial cells eg shigella
71
What is e.coli
Gram negative bacilli
72
What are the 4 E. coli subsets that cause disease
Enterotoxigenic
Enterohaemorrhagic
Enteroinvasive
Enteroaggregative
73
What are the two types of enterotoxigenic e.coli
Heat labile toxin - increase cAMP and increase chloride secretion
Heat stable toxin - increase cGMP and increase chloride secretion
74
What are you at risk of with enterohaemorrhagic E. coli
Haemolytic uraemic syndrome
75
What can shigella cause
Dysentery and HUS
76
What does campylobacter jejuni cause
Secretes toxins causing diarrhoea
Invades colonic epithelium causing dysentery
Reproduces in mesenteric lymph nodes causing enteric fever
77
What is salmonella enteritidis in
Found in contaminated chicken and beef
78
What does salmonella typhi cause
Causes systemic typhoid fever, multiplies within macrophages of intestinal Peyers patches, spleen, liver, bone marrow
Chronic carriers have asymptomatic gallbladder colonisation
79
What is C diff associated with
Antibiotic associated
Especially 3rd generation cephalosporins
80
The multiple toxins from c.diff lead to
Ribosylation of small GTPases
Disruption of the epithelial cytoskeleton
Tight junction barrier loss
Cytokine release
Apoptosis
Leads to pseudomembranous colitis
81
In c.diff what it pseufomembranous colitis
An exudate with inflammatory debris and neutrophils at sites of mucosal injury
Pattern of exudate from mucosal crypts looks like a volcano eruption
82
With Vibrio cholerae what are the 2 virulence factors
Flagellar proteins - increase motility
Cholera toxin - has 6 subunits
1 A subunit - acts as an enzyme that permanently activates Gs alpha subunit
6 B subunits bind to epithelial cell
Membranes - endocytosis of toxin
83
How does the toxin in vibrio cholerae work
Binds to epithelial cells
Activates adenylyl cyclase
Increased cAMP
Opens chloride channels
Massive secretion of chloride sodium and hco3
Osmotic h2o loss
Leads to secretory diarrhoea
84
5 virulence factors of streptococcal
Rodlike surface m proteins and a polysaccharide capsule - prevent phagocytosis
Pneumolysin - lyses host cells, wastes host complement
Exotoxins - produce rash in scarlet fever
Proteases - degrade chemotactic peptides and immunoglobulins
Lactic acid
85
4 virulence factors for Candida albicans
Phenotype switching - to adapt to host environment
Adhesion to host cell
Production of enzymes - degrade extracellular matrix proteins and may aid intracellular survival
Secretion of adenosine - blocks neutrophil de granulation
86
What is plasmodium falciparum
Parasite that causes malaria
87
In malaria what happens with inoculated sporozites
Releases from the salivary glands of female mosquito
Immediately invade the liver
88
What does plasmodium falciparum cause
Splenomegaly
Severe anaemia
89
In an IVDU patient with osteomyelitis which organism is normally isolated
E.coli, pseudomonas, klebsiella
90
What organism causes pyogenic osteomyelitis in 80-90% patient s
Staph aureus
Except on IVDU and patients with gi Tracy infections then it is e.coli, pseudomonas, klebsiella
91
What is gingivostomatitis
An infection of the mouth and gums that leads to swelling and sores
92
Which hepatitis are transmitted foecal oral route
Hepatitis A and E
“Vowels hit the bowels”
93
What is chlamydia
Gram negative bacterium that is an obligate intracellular parasite
94
What is the main causative organism in septic arthritis in older children and adults
Staph
95
What is the most common organism and septic arthritis in late adolescence and young adults
Gonococcus
96
What organism is the greatest cause of septic arthritis in sickle cell patients
Salmonella - at any age
97
Which organism is main cause in septic arthritis in children <2
H.influenza
98
Which part of the CNS does polio affect
Anterior horn motor neurons of the spinal cord
Posterior horns and cranial motor nuclei sometimes involved
99
Describe the characteristics of the measles rash
Generalised maculopapular erythematous rash
Starts in head and trunk before spreading to cover most of the body
100
What does measles cause in the mouth
Koplik spots
Ulcerated mucosal lesions near the duct of stensen, are marked by necrosis, neutrophilic exudate and neovascularization
101
What is bacillus anthracis
Large spore forming gram positive rod
102
What are the 3 main syndromes caused by anthrax
Cutaneous anthrax
Inhalations anthrax
GI anthrax
103
Which syndrome of anthrax can lead to bacteraemia and death
Inhalational anthrax
104
What is the most common infection to complicate burns
Pseudomonas aeruginosa
105
The diagnosis of EBV depends on what investigations
1. Lymphocytosis with characteristic atipical lymphocytes in the peripheral blood
2. Monospot test
3. Specific antibodies for EBV
106
In immune competent patients what can EBV cause
Can be asymptomatic
Mononucleosis pneumonitis
Hepatitis
Splenitis
Meningitis
Encephalitis
107
In patients with immunodeficiency what can EBV cause
EBV positive tumours
B cell lymphoma
Nasopharyngeal ca
Hodgsons and non Hodgkin lymphomas
Burkitt lymphoma
108
What type of paralysis does c.botulinum cause
Flaccid paralysis
Prevents release of ach at the neuromuscular junction
109
What type of paralysis is caused by c.tetani
Spastic paralysis
Blocking release of gamma aminobutryic acid a neurotransmitter that inhibits motor neurones
110
What are rickettisiale infections
Vector borne obligate intracellular bacteria that cause typhus
111
What part of the body does ricketisial
Bacteria infect
Vascular endothelial cells of the brain and lung
112
What type of immunity is important in clearing rickettsiae infections
T lymphocyte mediated
