Superficial and necrotic infections 2 Flashcards
GAS stands for
Group A staphylococcus
fever is always present in necrotising fascitis
false- sometimes is sometimes isn’t
how common is nf?
rare- 500 cases pa in the UK
clinical presentation of nf?
red, hot, swollen and very painful
severely unwell
what can nf lead to?
septic shock
common predisposing factors to NF?
trauma
diabetes
IV drug use
>60
why does diabetes predispose you to nf?
poor blood flow
most common bacterial cause?
GAS- S.pyrogenes
mortality with nf?
variable
30%
what is needed in nf treatment
aggressive AB management and surgical intervention
vancomycin will target any gram _____ organisms
positive
metronidazole will target any ______ that could be causing nf?
anaerobes
what ab is shown to affect virulence factors in GAS
clindamycin
why is it rare for gas to form nf?
needs a large amount of virulence factors
5 virulence factors GAS (s.pyrogenes) must acquire to become nf
- coat in host factors to disguise from immune system
- produce SpyCEP to break down ILA (immune evasion)
- phagocyte recognition- cause apoptosis of phagocytes by releasing streptomycin O
- neutrophil nets breakdown via sda1
- hyaluronic acid capsulate avoid immune system- molecular mimicry
what can the GAS coat itself in to avoid recognition?
host factors- fibrinogen
plasmin
immunoglobulins
what do GAS produce to break down ILA?
SpyCEP
what can GAS produce to cause phagocyte apoptosis
streptolycin O
how does GAS breakdown neutrophils nets?
the net is composed of chromatin which SD.pyrogenes can breakdown by producing sda1
what is the process called which produces the chromatin net from phagocytes
ketosis
why does the hyaluronic acid capsule disguise GAS?
as HA can be found in connective tissue- immune system cant recognise the bacteria if its coated intros
___% of nf cases have no observable break in the skin?
10
attachment is aided by?
pili
lipotechoic acid
F and M proteins
immune evasion is via which molecules
M protein
hyaluronic capsule
streptolysins
SpyCEP
