Management of methicillin sensitive Staphylococcus aureus bacteraemia in an antimicrobial stewardship age

Background: Methicillin sensitive Staphylococcus aureus bacteremia (MS-SAB) is associated with significant morbidity and mortality. Long courses of intravenous antibiotics are the traditionally recommended mainstay of treatment but are often not completed in clinical practice. Shorter courses are potentially attractive from an antimicrobial stewardship and resource perspective, but require a good evidence base.

Methods: A retrospective audit of MS-SAB management within Newcastle-upon-Tyne Hospitals NHS Foundation Trust (2016-17). Laboratory database was used to identify all cases of MS-SAB. Demographic details, risk factors and management were recorded from patient records. Outcomes were defined as 90d recurrence-free survival, 30d mortality, 30-90d mortality and recurrence before 90d.

Results: A total of 281 adult cases were identified with adequate data available for review. Predictors of early (30d) mortality were: age, 71.4y vs 58y p<0.001; HAI, 21.4% vs 8.6% p=0.003; osteo-articular infections, 2.5% vs 17.1% p=0.016; but not antibiotic choice. In cases surviving 30d (n=238), median antibiotic durations were: intravenous 10d (range, 0-115), total 18d (0-316). 83% received ≥14d total, 41% received ≥14d intravenous. Receiving <9d intravenous (OR 3.33 (95%CI 1.01- 10.95) or <14d total therapy (OR 4.19 (1.37-12.84) was predictive of recurrent bacteraemia, as was non-beta-lactam therapy (16% vs 4%, p=0.006), and poor CRP response at end of intravenous therapy (68% vs 35% of peak CRP, p<0.001).

Conclusions: These data suggest lower durations (9-14d) of intravenous therapy could be safe in MS-SAB, however very short courses (<9d) are associated with worse outcomes. This new evidence helps inform guidelines, balancing optimised patient outcomes alongside improved antimicrobial stewardship.