Superficial and necrotic infections 2

Question 1

GAS stands for

Answer 1

Group A staphylococcus

Question 2

fever is always present in necrotising fascitis

Answer 2

false- sometimes is sometimes isn’t

Question 3

how common is nf?

Answer 3

rare- 500 cases pa in the UK

Question 4

clinical presentation of nf?

Answer 4

red, hot, swollen and very painful

severely unwell

Question 5

what can nf lead to?

Answer 5

septic shock

Question 6

common predisposing factors to NF?

Answer 6

trauma
diabetes
IV drug use
>60

Question 7

why does diabetes predispose you to nf?

Answer 7

poor blood flow

Question 8

most common bacterial cause?

Answer 8

GAS- S.pyrogenes

Question 9

mortality with nf?

Answer 9

variable

30%

Question 10

what is needed in nf treatment

Answer 10

aggressive AB management and surgical intervention

Question 11

vancomycin will target any gram _____ organisms

Answer 11

positive

Question 12

metronidazole will target any ______ that could be causing nf?

Answer 12

anaerobes

Question 13

what ab is shown to affect virulence factors in GAS

Answer 13

clindamycin

Question 14

why is it rare for gas to form nf?

Answer 14

needs a large amount of virulence factors

Question 15

5 virulence factors GAS (s.pyrogenes) must acquire to become nf

Answer 15

1. coat in host factors to disguise from immune system
2. produce SpyCEP to break down ILA (immune evasion)
3. phagocyte recognition- cause apoptosis of phagocytes by releasing streptomycin O
4. neutrophil nets breakdown via sda1
5. hyaluronic acid capsulate avoid immune system- molecular mimicry

Question 16

what can the GAS coat itself in to avoid recognition?

Answer 16

host factors- fibrinogen
plasmin
immunoglobulins

Question 17

what do GAS produce to break down ILA?

Answer 17

SpyCEP

Question 18

what can GAS produce to cause phagocyte apoptosis

Answer 18

streptolycin O

Question 19

how does GAS breakdown neutrophils nets?

Answer 19

the net is composed of chromatin which SD.pyrogenes can breakdown by producing sda1

Question 20

what is the process called which produces the chromatin net from phagocytes

Answer 20

ketosis

Question 21

why does the hyaluronic acid capsule disguise GAS?

Answer 21

as HA can be found in connective tissue- immune system cant recognise the bacteria if its coated intros

Question 22

___% of nf cases have no observable break in the skin?

Answer 22

10

Question 23

attachment is aided by?

Answer 23

pili
lipotechoic acid
F and M proteins

Question 24

immune evasion is via which molecules

Answer 24

M protein
hyaluronic capsule
streptolysins
SpyCEP

Question 25

Effect of NSAIDs on S.pyrogenes recruitment in a bruise?

Answer 25

study which inoculated an animal that has been bruised with s.pyrogenes
one group take NSAIDs and another doesn’t
the group with NSAIDS had a higher GAS accumulation at the site

Question 26

why does NSAIDS increase the accumulation of s.pyrogenes at the bruise site

Answer 26

when you bruise you produce fermenting which is a filament that’s unregulated after trauma

GAS uses fermenting as a tether and is attracted to it.
NSAID increase the risk of this happening

Question 27

before the cause of NF is known how do we treat it?

Answer 27

empirical broad spectrum antibiotics

vancomycin or linezolid AND carbapenem AND clindamycin

Question 28

treatment of NF caused by GAS?

Answer 28

surgical debridement

benzylpenicillin AND clindamycin

Question 29

what if patients with NF caused by GAS has a penicillin allergy?

Answer 29

vancomycin mono therapy can be used.