Bacterial Virulence Flashcards
where might bacteria reside ?
hair follicle
sebaceous gland
sweat pore
how might an S. aureus skin infection present ?
rash
folliculitis
abscess
carbuncle
impetigo
scalded skin syndrome
is S. epidermis gram + or -
negative
what are S. epidermis infections associate with ?
foreign devices ie catheter
these are nosocomial infections/ immunocompromised
what are the virulence factors
adhesin (enables binding)
invasin (enables organism to invade host cell)
impedin (enables the organism to avoid host defences)
aggressin (damage directly)
modulin (damage indirectly)
what is toxinoses ?
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)
how does TSST-1 cause sickness ?
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
what is the diagnostic criteria for Toxic Shock Syndrome ?
fever, myalgia, headache, nausea
diffuse macular rash and desquamation
(diffuse macular erythroderma)
hypotension, <90
more than 3 organ systems involved
what is Panton Valentine Leukocidin ?
specific secreted proteins that form one functional complex that attacks white blood cells
-associated with severe skin infections
what is the complex of PVL , alpha toxin, CA-MRSA responsible for ?
necrotising pneumonia
what is necrotising pneumonia ?
a severe complication of quite mild infections due to destruction of immune cells
what streptococcal group is associated with sore throat and scarlet fever ?
S. pyogenes
what type of skin infection can you get with S. pyogenes ? (GAS - group A)
impetigo
cellulitis
necrotising fasciitis
impetigo infection
superficial and localised
entry point is a small defect in the skin
stratum corneum
cellulitis infection
deeper skin infection
invasion of the dermis
and subcutaneous fat
erysipelas - upper dermis
fever rigors and nausea
necrotising fasciitis
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
where are S. pyogenes infection normally found?
in the pharynx , can also adhere to skin
responsible for a range of diseases
variation in diseases and virulence is the result of the variation in the genes encoded by a pathogen
word.
what do toxinoses and opportunistic infections depend on ?
genotype AND expression of virulence proteins
