Retrospective Comparative Study of Cefazolin and Oxacillin in MSSA Infections in Patients with End-Stage Renal Failure and Dialysis.

Background Bloodstream infections due to methicillin-susceptible Staphylococcus aureus (MSSA-BSI) remain associated with considerable morbidity and mortality, especially among patients with end-stage renal disease (ESRD) and those undergoing dialysis. Oxacillin is generally considered the standard first-line therapy, although cefazolin may offer comparable efficacy with improved tolerability.   Methods We performed a single-center, retrospective observational study at AOU Modena, including adult ESRD and dialysis patients with MSSA-BSI treated with definitive therapy using either oxacillin or cefazolin. The original cohort comprised cases diagnosed between 2021 and 2023; for the present thesis, we extended the analysis to patients treated between 2017 and 2019. The primary outcome was a composite of mortality and recurrence at 30 and 90 days. Secondary outcomes included individual components of the primary outcome, persistent bacteremia for ≥5 days, intensive care unit (ICU) admission and adverse drug reactions.     Results From 2021 to 2023, 60 patients fulfilled the inclusion criteria, of whom 51 received oxacillin and 9 received cefazolin. Thirty-day mortality was 23.3% overall, with no statistically significant difference among groups (11.1% in the cefazolin group versus25.5% in the oxacillin group, p0.347). At 90 days, mortality reached 33.3% in both groups. Two recurrences were reported, both in patients treated with cefazolin. Persistent bacteremia was relatively frequent in both arms (58% OXA vs 66.7% CEF). Adverse events occurred only in oxacillin-treated patients (3.9%). Hospital stay was shorter for cefazolin (median 14 vs 23 days, p=0.022).   The extended 2017–2019 cohort included 40 additional patients, 35 treated with oxacillin and 5 with cefazolin. In this period, 13 patients died during follow-up (10 on oxacillin and 3 on cefazolin), and only one recurrence was recorded, in an oxacillin-treated patient. No adverse drug reactions were observed in either group.   Conclusions In our preliminary results, cefazolin demonstrated efficacy comparable to oxacillin but was better tolerated and associated with a trend toward shorter hospitalization. These findings suggest that cefazolin may represent a valuable therapeutic alternative in ESRD and dialysis patients with MSSA-BSI, but to confirm these results larger prospective randomized studies are necessary.