Bacterial Virulence

Question 1

where might bacteria reside ?

Answer 1

hair follicle
sebaceous gland
sweat pore

Question 2

how might an S. aureus skin infection present ?

Answer 2

rash
folliculitis
abscess
carbuncle
impetigo
scalded skin syndrome

Question 3

is S. epidermis gram + or -

Answer 3

negative

Question 4

what are S. epidermis infections associate with ?

Answer 4

foreign devices ie catheter

these are nosocomial infections/ immunocompromised

Question 5

what are the virulence factors

Answer 5

adhesin (enables binding)

invasin (enables organism to invade host cell)

impedin (enables the organism to avoid host defences)

aggressin (damage directly)

modulin (damage indirectly)

Question 6

what is toxinoses ?

Answer 6

discrete disease associated with single protein component, toxin or exotoxin

ie

TSST - 1 ( toxic shock syndrome toxin-1)

staphylococcal food poisoning (SeA, SeB and SeC)

SSS (scalded skin syndrome - ETA and ETB toxins target Desmoglein)

Question 7

how does TSST-1 cause sickness ?

Answer 7

it actives 1 in 5 T cells

the antigen is not processed by PMN, it bind directly to MHCII complex ie outside conventional binding groove
and so there is a massive release of cytokines and inappropriate immune response

Question 8

what is the diagnostic criteria for Toxic Shock Syndrome ?

Answer 8

fever, myalgia, headache, nausea

diffuse macular rash and desquamation
(diffuse macular erythroderma)

hypotension, <90

more than 3 organ systems involved

Question 9

what is Panton Valentine Leukocidin ?

Answer 9

specific secreted proteins that form one functional complex that attacks white blood cells

-associated with severe skin infections

Question 10

what is the complex of PVL , alpha toxin, CA-MRSA responsible for ?

Answer 10

necrotising pneumonia

Question 11

what is necrotising pneumonia ?

Answer 11

a severe complication of quite mild infections due to destruction of immune cells

Question 12

what streptococcal group is associated with sore throat and scarlet fever ?

Answer 12

S. pyogenes

Question 13

what type of skin infection can you get with S. pyogenes ? (GAS - group A)

Answer 13

impetigo

cellulitis

necrotising fasciitis

Question 14

impetigo infection

Answer 14

superficial and localised

entry point is a small defect in the skin

stratum corneum

Question 15

cellulitis infection

Answer 15

deeper skin infection

invasion of the dermis
and subcutaneous fat

erysipelas - upper dermis

fever rigors and nausea

Question 16

necrotising fasciitis

Answer 16

invasive strep A (iGAS)
penetrate mucous membrane and develop in lesion

severe infection

rapid destruction of connective tissue

with TSLS super antigen can lead to toxic shock

Question 17

where are S. pyogenes infection normally found?

Answer 17

in the pharynx , can also adhere to skin

responsible for a range of diseases

Question 18

variation in diseases and virulence is the result of the variation in the genes encoded by a pathogen

Answer 18

word.

Question 19

what do toxinoses and opportunistic infections depend on ?

Answer 19

genotype AND expression of virulence proteins