Contemporary use of cefazolin for MSSA infective endocarditis: analysis of a national prospective cohort

Objective: The aim of this study was to assess the real use of cefazolin for methicillin-susceptible S. aureus (MSSA) infective endocarditis (IE) in the Spanish National Endocarditis Database (GAMES) and to compare it with antistaphylococcal penicillins (ASP).Methods: Prospective cohort study with retrospective analysis of a cohort of MSSA IE treated with cloxacillin and/or cefazolin. Outcomes assessed were: relapse; intra-hospital, overall and endocarditis-related mortality; and adverse events. Risk of renal toxicity with each treatment was evaluated separately.Results: We included 631 IE episodes caused by MSSA treated with cloxacillin and/or cefazolin. Antibiotic treatment was cloxacillin, cefazolin or both in 537(85%), 57(9%) and 37(6%) episodes respectively. Patients treated with cefazolin had significantly higher rates of comorbidities (median Charlson Index 7, p<0.01) and previous renal failure (57.9%, p<0.01). Patients treated with cloxacillin presented higher rates of septic shock (25%, p=0.033) and new-onset or worsening renal failure (47.3%, p=0.024) with significantly higher rates of in-hospital mortality (38.5%, p=0.017). One-year IE related mortality and rate of relapses was similar between treatment groups. None of the treatments were identified as risk or protective factors.Conclusion: Our results suggest that cefazolin is a valuable option for the treatment of MSSA IE, without differences in one-year mortality or relapses compared with cloxacillin and might be considered equally effective.