Cloxacillin versus cefazolin for meticillin-susceptible Staphylococcus aureus bacteraemia (CloCeBa): a prospective, open-label, multicentre, non-inferiority, randomised clinical trial

BACKGROUND: Although widely used, cefazolin efficacy for the treatment of meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia has not thus far been investigated in a clinical trial. In this study, we aimed to compare the efficacy and safety of cefazolin with that of cloxacillin in patients with MSSA bacteraemia. METHODS: We conducted an open-label, non-inferiority, randomised clinical trial in 21 university and non-university hospitals in France in adults (aged ≥18 years) with MSSA bacteraemia, without intravascular implant or suspicion of CNS infection. Participants were randomly assigned (1:1) to receive intravenously cefazolin (25-50 mg/kg every 8 h) or cloxacillin (25-50 mg/kg every 4-6 h) for the first 7 days of therapy using computer-generated blocks of various sizes and stratification on vascular-access associated bacteraemia and centre. Subsequent treatment was left to the choice of the investigator (total duration ≥14 days). The primary endpoint was a composite of sterile blood cultures at day 3 (day 5 for endocarditis) without relapse of bacteraemia, survival, and clinical success at day 90, and was assessed in the intention-to-treat population. A non-inferiority margin of 12% was chosen. This trial is registered on ClinicalTrials.gov (NCT03248063) and is complete. FINDINGS: Between Sept 5, 2018, and Nov 16, 2023, 315 participants were enrolled and assigned to cefazolin (n=158) or cloxacillin (n=157); 12 participants were excluded from analysis in the cefazolin group, and 11 in the cloxacillin group (final population of 146 in each group). Mean age was 62·7 years (SD 16·4), 215 (74%) participants were male, and race or ethnicity data were not collected. Median Pitt score was 0 (IQR 0-0). The primary endpoint was met in 109 (75%) of 146 participants in the cefazolin group versus 108 (74%) of 146 participants in the cloxacillin group (treatment difference -1%; 95% CI -11 to 9; p=0·012). At the end of study treatment, 22 (15%) of 146 participants assigned to cefazolin and 40 (27%) of 146 participants assigned to cloxacillin had had a serious adverse event (p=0·010). Acute kidney injury occurred more frequently in participants assigned to cloxacillin (15 [12%] of 128) than in those assigned to cefazolin (one [1%] of 134; p=0·0002). INTERPRETATION: Cefazolin constitutes an alternative to cloxacillin for the treatment of MSSA bacteraemia, offering non-inferior clinical efficacy and potentially enhanced tolerability. FUNDING: French Ministry of Health.