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Micro - Staphylococci (ii) S Aureus (Systemic infections (endocarditis…
Micro - Staphylococci (ii) S Aureus
Systemic infections
BSI
endocarditis
usually secondary to BSI
investigate for primary focus (e.g. IV line site)
fever
rapidly progressive
Tx: prolonged antibiotics + possible surgical replacement of valve
pneumonia
secondary to BSI
haematogenous spread
septic emboli, Ive line site, right-sided endocarditis
risk factors
viral resp infection (influenza/measles)
CF
ventilation (ICU)
aspiration
osteomyelitis
haematogenous (secondary to local trauma)
usually in vertebrae (adults) or metaphyses of long bone (children)
Dx: FNA/bone scan
septic arthritis
hot swollen joint
commonly in joints affected by met spread (knee, hip, elbow, shoulder)
secondary to BSI/endocarditis
deep abscesses (e.g. brain, liver)
Toxin-mediated infections
TSS
rapid dramatic fulminant (sudden) onset
NB to recognise quickly
pyrexia, hypotension, rash + subsequent desquamation (aka keratinisation, esp on palms + soles)
renal failure, disorientation, severe myalgia + increased creatine phosphokinase (indicates muscle stress/injury)
Do FBC, U+E, lactate, wound swab if skin lesion present, blood (rarely causes by BSI), cervix/vagina swab
Tx: rapid IV antibiotics, source control, debridement (removal of dead/damage/infected tissue), possibly resus + critical care
Gastroenteritis
food poisoning
caused by contaminated food/food handlers, poor hand hygiene
mediated by enterotoxins
8 types
stable: up to 100 degrees, acid + salt resistant
rapid symptom onset, usually only lasts 1 days
NO ANTIBIOTICS, supportive Tx only (e.g. rehydration)
Scalded skin syndrome
MRSA
due to altered PBP (PBP2a coded by MecA gene)
gene carried on a mobile genetic element (Staphylococci cassette chromo)
resistant to most B-lactams
usually HAI
Tx: glycopeptides (vancomycin/teicoplanin)
! GRSA emerging - Tx = daptomycin, linezolid or tetracyclines
can be CAI
usually manifests as a skin infection or necrotising pneumonia
toxin-mediated - Panton Valentine Leucocidin (PVL)
virulence factor
rarely in MSSA or nosocomial MRSA
linked to severe skin infections + pneumonia
often in young healthy patients
less drug resistant, but more virulent
e.g. USA300 strain in N America
Management
Hx + clinical exam
find source + spread
skin breaks/abscesses
murmurs/pericarditis
osteomyelitis
investigations
blood if systemic symptoms
if BSI +ve do ECHO + repeat 2 days after Tx
radiology
microbiology cultures
day 0: incubate specimen @ 37 degrees
day 1: gram stain, culture plates, PCR (quicker), review patient
day 2-3: read agar cultures, coag test, give results
day 3-4: antibiotic susceptibility, alter empiric tx if needed
if MRSA - precautions + decolonisation
ECHO for endocarditis (goes down oesophagus)
abscess tissue/pus better than swab
sputum or BAL for pneumonia
joint fluid for septic arthritis
sample of ingested food if gastroenteritis
Tx
choice, route + duration varies
nothing if mild (boils, folliculitis)
antibiotics for 7-10 days for skin/soft tissue infections + RTIs
2+ wks for BSI
4-6 wks for endocarditis
6 wks for septic arthritis
1st line = 1GC (flucloxacillin/cefazolin) if susceptible