432: EFFICACY OF TARGETED VS. NONTARGETED BETA-LACTAM THERAPY FOR MSSA BACTEREMIA: A MATCHED COHORT STUDY

Abstract

Introduction: Methicillin-susceptible Staphylococcus aureus (MSSA) is implicated in blood stream infections with high morbidity and mortality. Targeted treatment (TT) with nafcillin or cefazolin is considered first-line therapy, however patients may receive broad spectrum therapy for MSSA bacteremia for various reasons. We hypothesize non-targeted beta-lactams (NT) are less effective for blood culture clearance compared to TT for MSSA bacteremia. Methods: Critically ill patients >18 years old with an MSSA positive blood culture between 7/1/2014 and 12/31/2020 were included. Patients were identified retrospectively through the electronic medical record and must have received either a NT (ampicillin/sulbactam, ceftriaxone, cefepime, piperacillin/tazobactam, meropenem) or TT. The TT cohort included the receipt of or de-escalation to nafcillin or cefazolin within 72 hours of antibiotic initiation. Patients with lack of follow-up blood cultures, death, or discharge within 48 hours of positive culture were excluded. Patients were matched according to age, Charlson Comorbidity Index (CCI), presence of a central line, and source of bacteremia. The primary outcome was duration of bacteremia. Secondary outcomes included hospital and intensive care unit (ICU) length of stay (LOS) and inpatient mortality. Results: Of 423 patients, 178 were included based on matching criteria. The majority of patients were male (63%) and Caucasian (92%) with a median age of 56 (interquartile range [IQR], 47-65). Median CCI was 5 in both groups (IQR, 3-8). The most frequent NT were piperacillin/tazobactam (56%) and cefepime (34%). There was no significant difference in duration of bacteremia (3.4 vs 3.4 days, p=0.653), hospital LOS (18.9 vs 26.4 days, p=0.071), or ICU LOS (5.3 vs 5.9 days, p=0.966) in the TT vs NT cohorts, respectively. Patients in the TT cohort had significantly lower mortality compared to those in the NT cohort (12.4% vs 24.7%, p=0.034). Conclusions: ICU patients who received TT or NT had similar duration of bacteremia, hospital LOS, and ICU LOS. Exposure to NT was associated with increased mortality. Although these results should be validated prospectively, clinicians should be cognizant of this risk when evaluating those with MSSA bacteremia and consider de-escalation to TT as soon as clinically appropriate.