Twice daily cefazolin is effective for treatment of serious methicillin-sensitive Staphylococcus aureus infection in an outpatient parenteral antimicrobial therapy program

Background: The use of cefazolin for infections caused by Staphylococcus aureus has been demonstrated to be effective, and associated with fewer adverse effects compared with anti-staphylocccal penicillins; however, use of cefazolin on outpatient parenteral antimicrobial therapy (OPAT) programs often requires the use of continuous infusions. We report the outcomes of patients with serious infections caused by methicillin-sensitive S. aureus (MSSA) treated using twice daily cefazolin by a large tertiary hospital OPAT program. The aim of this study was to evaluate the safety, efficacy and outcomes after 90 days of follow up for patients with serious infections caused by MSSA treated with twice daily cefazolin by our OPAT program. Methods: A retrospective analysis of clinical outcomes of cases treated for a serious infection proven to be caused by MSSA treated with cefazolin monotherapy on the OPAT program at a tertiary hospital between January 2010 and July 2016 (6.5 years). Outcome measures included readmission rate, adverse drug reactions and clinical cure. Results: A total of 111 cases of serious MSSA infection were treated with cefazolin in the OPAT service during the study period, including 52 with peripheral or vertebral osteomyelitis and 13 with infective endocarditis; 56 patients had bacteraemia. Median duration of intravenous antibiotic therapy was 41 days, and the median proportion of intravenous therapy administered via OPAT was 69%. Two patients had recurrence of infection within 90 days, but were in the setting of retained prosthetic material. A total of 4% of patients experienced an adverse drug reaction. No cases of antibiotic failure were identified. Conclusions: The use of twice daily cefazolin for serious MSSA infection on an OPAT program is safe and effective. Further study is needed to assess for noninferiority to conventional treatment regimes.