Outcomes of vancomycin plus a {beta}-lactam versus vancomycin only for the treatment of methicillin-resistant Staphylococcus aureus bacteremia [PublishAheadOfPrint]

The objective of this retrospective study was to compare the rates of treatment failure, which was a composite of clinical and microbiologic failure, of patients receiving vancomycin and a β-lactam to those receiving vancomycin only for MRSA bacteremia. Patients 16 to 89 years of age with MRSA bacteremia admitted to a university-affiliated hospital from January 1^st, 2014 to December 31^st, 2016 were screened for study inclusion. Patients were eligible if they received >48 hours of vancomycin and a β-lactam (combination group) or vancomycin only (standard group) within 48 hours following bacteremia onset. 182 patients were screened: 47 were included in the standard group and 63 in the combination group. The combination group had a higher baseline body mass index (29.2 ± 8.0 kg/m² vs 25.8 ± 7.1 kg/m², p=0.022), acute physiologic assessment and chronic health evaluation-II (APACHE-II) score (median [interquartile range], 21 (15-26) vs 16 (10-22), p=0.003), and incidence of septic shock (31.8% vs 14.9%, p=0.047). Using multivariate analysis, combination therapy was the only variable that decreased treatment failures (odds ratio [95% confidence interval], 0.337 [0.142 to 0.997]), while vancomycin MIC >1 mg/L and male gender increased treatment failures (4.018 [1.297 to 12.444] and 2.971 [1.040 to 8.488], respectively). 30-day mortality rates (15.0% vs 14.9%, p=1.000) and incidence of adverse drug events (19.1% vs 23.4%, p=0.816) were not statistically different between the combination and standard groups. Combination therapy of vancomycin with a β-lactam led to significantly fewer treatment failures than vancomycin monotherapy for MRSA bacteremia.

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