Staph aureus
bacteremia management in a nutshell
- Management is never straightforward - we suggest
that every case is referred to an infectious diseases consultant
- If there's any doubt about the diagnosis (e.g.,
only 1/2 bottles positive or > 24 hours to become positive) then repeat the
blood cultures BEFORE you start treatment
- ALWAYS do the following at baseline:
- Remove existing IV and/or arterial lines (these prolong bacteremias)
- ECG looking for new
evidence of any degree of heart block (sign of aortic root abscess in endocarditis)
- If present, this is a medical emergency and
requires an urgent echocardiogram
- MSU for culture and microscopy
- S. aureus in the urine is usually
NOT a sign of primary urinary tract infection, but rather spillover
of a high organism burden from the blood into the urine indicating a
worse prognosis (e.g., in endocarditis)
- Glomerular red cells are a
Duke minor criteria for
diagnosing endocarditis
- Rheumatoid factor on serum (Duke minor criteria
for diagnosing endocarditis)
- ALL ADULTS must have an echocardiogram:
- Go straight to a TOE from the outset if any of:
- Endocarditis is
suspected clinically
- Prosthetic or known
abnormal heart valves
- Pacemaker or similar device
- The surveillance blood culture on day 3-4
is still positive
- Community acquired bacteremia with no
apparent focus
- You're unlikely to get good views on TTE
(previous poor TTE, emphysema, obese)
- A TTE is OK first off in adults if:
- Endocarditis
seems unlikely and you think you'll get good views
- Go on to a TOE if the TTE is remotely
suspicious (e.g., minor regurgitation, possible vegetations) OR you
didn't get clear views
- Reserve an echocardiogram in CHILDREN
for any of:
- All children from high risk groups for
rheumatic fever (eg, Indigenous children)
- Known intra-cardiac / valvular
abnormalities (consider that neonates may have undiagnosed
abnormalities)
- Prolonged fever or persistently positive
blood cultures (after 2-4 days of treatment)
- ANTIBIOTIC DOSES for normal renal function (assuming susceptibility):
- Different rules apply in the presence of
prosthetic heart valves (ask ID)
- Check children's doses in the Australian
Antibiotic Guidelines
- All drugs require adjustment in the presence of
renal failure
- PSSA (penicillin
sensitive S. aureus, about 5% of isolates)
- Penicillin 1.8g IV 4hly if endocarditis not
suspected
- Penicillin 2.4g IV 4hly if endocarditis suspected
clinically
- MSSA (methicillin
sensitive S. aureus, the commonest isolate)
- Flucloxacillin
or dicloxacillin 2g IV 6hly if endocarditis not suspected
- Flucloxacillin
or dicloxacillin 2g IV 4hly if endocarditis highly suspected
- PSSA or MSSA (if patient penicillin allergic)
- Non-anaphylaxis
- Use cephalothin (NOT cephazolin, which is
inferior) at same dose as flucloxacillin
- Anaphylaxis
- MRSA (methicillin
resistant S. aureus)
- Vancomycin
25mg/kg to maximum 1.5g dose IV 12hly (for GFR > 90 mL/min; else
adjust down)
- If vancomycin MIC >=2, then alternatives
to vancomycin may be preferred; consult ID
- Sensitivities unknown (i.e., provisional
diagnosis of S. aureus by lab or suspected clinically)
- Treatment with Vancomycin to cover MRSA
PLUS either flucloxacillin or cephalothin (if allergy) as this
provides a survival benefit in MSSA and PSSA cases
- SURVEILLANCE BLOOD CULTURES at 72-96 hrs
- Mandatory. Collect on all patients 72-96 hours
after starting treatment.
- Best guide to prognosis (if positive,
suggests deep-seated infection that often warrants further
investigation looking for hidden sites like psoas abscess, discitis
or sacroiliac joint septic arthritis)
- DURATION OF TREATMENT (assuming surveillance
culture negative; else, ask ID)
- *If using vancomycin, consider adding 2 weeks
in most instances
- Endocarditis native
valves - 6 weeks (maybe less for tricuspid endocarditis in IVDUs)
- Osteomyelitis or
discitis - 6 weeks IV
- Septic arthritis - minimum 4 weeks IV +
consider 2 weeks orals (or 6 weeks IV, especially if using vancomycin)
- Re-treatment of a relapsed case - 6 weeks IV
- Most other sites, including pneumonia, skin and
soft tissue (and unknown focus in community cases) - Minimum 4 weeks (we
like to see the CRP has normalised by this time also)
- Prosthesis in situ (e.g., total hip
replacement) - add 2 weeks (to maximum of 6 weeks)
- Removable focus that was pulled out promptly with
negative surveillance culture AND echo has reliably excluded endocarditis - 2 weeks IV MINIMUM
(this includes peripheral IV cannulae, arterial lines, urinary
catheters)
- REVIEW ALL PATIENTS with a repeat blood
culture 4 weeks after stopping treatment to detect relapses