Duration of therapy for S. aureus bacteraemia in adults

The duration of antibiotic therapy for adults with S. aureus bacteraemia depends on whether the patient has complications of infection.

Adults have complicated S. aureus bacteraemia if they meet any of the following criteria:

  • a positive blood culture result 48 hours after starting appropriate antibiotics (see also Persistent S. aureus bacteraemia)
  • fever 72 hours after starting appropriate antibiotics
  • abnormal valvular morphology or evidence of valvular lesions, regurgitation or endocarditis on transthoracic echocardiogram (TTE) or transoesophageal echocardiogram (TOE) – see Assessing and monitoring patients with Staphylococcus aureus bacteraemia
  • no identifiable source of infection or an identifiable source of infection that has not been addressed
  • evidence of metastatic infection (eg osteomyelitis, septic arthritis, pneumonia, lung abscess, endocarditis)
  • intravascular prosthetic material (eg pacemaker, prosthetic cardiac valve, prosthetic arteriovenous graft).

Treat adults with complicated S. aureus bacteraemia with at least 4 weeks of therapy; extend to 6 weeks if response to therapy is slow.

Treat adults with uncomplicated S. aureus bacteraemia (ie those who do not meet any of the above criteria) with 14 days of therapy.

There is extensive experience in using intravenous antibiotics to complete the total course of therapy for adults with S. aureus bacteraemia; this has been the standard of care and remains appropriate for many patients.

Switching from intravenous to oral therapy may be appropriate in carefully selected adults with S. aureus bacteraemia. The literature supporting a switch includes a relatively small number of participants cumulatively across both prospective and retrospective studies using a variety of oral regimens, including high-dose beta lactams, linezolid, trimethoprim+sulfamethoxazole and quinolones, with or without adjunctive rifampicinBupha-Intr, 2020Dagher, 2020Kouijzer, 2021Wald-Dickler, 2022. Further research is required to define the optimal time to switch, the conditions for switching and the most effective oral regimens.

In patients likely to tolerate and absorb oral medications, consider switching to oral therapy once blood culture results are negative, the patient is clinically and haemodynamically stable and, wherever possible, any surgical or procedural source control has been completed. Antibiotic choice and dosing are complex – seek expert advice. Therapeutic drug monitoring may be required if switching to therapy with high-dose oral antibiotics.

Patients who switch to oral therapy should receive close follow-up (usually weekly) during therapy to ensure treatment is tolerated and to identify any adverse effects or early evidence of relapse.