Microbiology Flashcards
when would you do a skin swab
skin broken and signs of infection
when would you take blood cultures for skin infection?
systemically unwell
fever, rigor, chills
tachycardia etc
skin commensals
staph epidermidis
staph aureus in 20-30%
corynebacterium
propionibacterium
what diseases can staph aureus cause
boils/carbuncles minor skin infection impetigo cellulitis infected eczema staph scalded skin syndrome
management of normal staph aureus, MRSA of skin and MRSA systemic
normal - fluclox oral
MRSA - skin doxy, co-trimox or clindamycin
MRSA - systemic IV vancomycin
whats the risk with clindamycin??
C diff
a patient presents with painful eczema and you suspect infection. the swab comes back and its staph epidermidis. do you commence fluclox?
no, theres no point as its a commensal and probably lives there. be careful though of patients with prosthetic joints or heart valves as epidermidis may infect there if systemic
alpha haemolysis produces?
greening
strep pneumoniae or viridans causing endocarditis
beta haemolysis produces?
complete discoloration
strep pyogenes or GAS
gamma haemolysis produces?
no haemolysis
gut commensals, ie enterococcus which may prove UTI n select specific cases
strep infection causes what diseases
Impetigo cellulitis erysipelas infected eczema necrotising fasciitis
managing GAS normally
penicillin works but fluclox is best as covers staph too in case
what is the exception to managing GAS and how is it managed
necrotising fasciitis, life threatening medical emergency
presents as pain way out of proportion to examination
send to theatre NOW
debride and remove necrosis and broad spectrum IV antibiotics to cover all bacteria if possible
when would you swab a leg ulcer
only in signs of infection, dont if its just a leg ulcer
What is the M antigen and what does it do
surface protein found on GAS
evades phagocytosis and opsonisation by destroying parts of complement
what superantigen in strep can lead to TSS
TSLS
what is SLS/SLO
haemolysin/cytolysin causing beta heamolysis and tissue tissue damage
can damage platelets, neutrophils and lymphocytes
what does protein A do
binds antibodies the wrong way round to prevent opsonisation/phagocytosis
what does coagulase do
formation of a clot to protect staph aureus from phagocytosis and enhance adhesion
what does alpha toxin and PVL do
destroys immune cells
name 2 adhesins
fibrinogen binding
fibro-nectin binding
what is necrotising pneumonia
complication of flu like illness, causing necrotising haemorrhagic pneumonia followed by deterioration and multisystem organ failure
describe how TSST-1 causes TSS
acts as superantigen to bind outside MHC II to activate high T cell response and massive cytokine release leading to symptoms of shock
recognition of TSS
fever of 39
diffuse macular erythroderma
<90mmHg
>3 organ systems involved
