Principles of directed therapy for S. aureus bacteraemia
For the treatment of Staphylococcus aureus bacteraemia, always use intravenous antibiotics initially. Many patients require prolonged intravenous antibiotic therapy (for at least 2 weeks, and often 4 to 6 weeks); ambulatory antimicrobial therapy may be appropriate after inpatient stabilisation and appropriate investigation. In carefully selected adults and children, oral continuation therapy may be appropriate – see Duration of therapy for Staphylococcus aureus bacteraemia.
Some patients with S. aureus bacteraemia will be critically ill. To ensure adequate drug exposure in these patients, modified dosages of cefazolin and flucloxacillin are recommended. This is because pharmacokinetics may be altered in critical illness (eg because of enhanced kidney clearance or changes in volume of distribution). Once the critical illness has resolved, consider switching to the standard dosage. If the isolate is not reported to have dose-dependent susceptibility to these drugs (ie susceptible dose dependent [SDD] or susceptible increased exposure [I or SIE]), it may also be appropriate to switch to the standard dose – seek expert advice.
For patients who have positive blood culture results on day 5 or later after starting treatment, see Persistent S. aureus bacteraemia.
Adding rifampicin to the primary regimen for S. aureus bacteraemia is not recommended because a large randomised controlled trial showed no benefit and a trend to increased adverse effects1. However, few patients with prosthetic valve endocarditis were included in this trial, so the results cannot be applied to these patientsThwaites, 2018.