Similar Efficacy Seen With Cefazolin and Oxacillin for High-Burden MSSA Infections

SAN FRANCISCO, CA—At IDWeek 2013, data from a retrospective, multi-centered observational study showed that cefazolin may have similar rates of clinical cure as oxacillin for methicillin-sensitive Staphylococcus aureus (MSSA) bloodstream infections (BSI), including treatment of high-burden infections.

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Anti-staphylococcal penicillins (eg, oxacillin, nafcillin) are the preferred treatment for MSSA BSI. Many clinicians are concerned about potentially higher failure rates with cefazolin due to the possible inoculums effect with β-lactamase A-producing MSSA isolates. Currently there are no prospective studies comparing the efficacy and tolerability of antistaphylococcal penicillins to cefazolin and the relative efficacy of different B-lactam antibiotics for the treatment of MSSA bloodstream infections are not well defined.

Sonia Nevrekar, PharmD, BCPS, from Midwestern University, Downers Grove, IL and Rush Medical Center, Chicago, IL, and colleagues designed a study to assess the clinical outcomes of patients treated with cefazolin or oxacillin for MSSA BSI, including those with high-burden disease (eg, endocarditis, endovascular infections). The team included 110 adult patients from author institutions with a MSSA BSI between January 2010 and August 1012 treated with cefazolin or oxacillin within 48 hours of finalized culture results.

Of the 110 patients included, 95 were treated with cefazolin and 15 with oxacillin.  High-burden infections were identified in 33.7% of the cefazolin-treated group and in 40% of the oxacillin-treated group. Forty-three patients in the cefazolin group and 6 patients in the oxacillin group were identified as having infections associated with central line/HD catheter. Patients with polymicrobial infections and those with penicillin allergies were excluded from this analysis.

The primary endpoint was in-hospital mortality (eg, death occurring during the index hospital admission in the time period from culture collection to discharge or death; backward stepwise logistic regression was performed to predict risk of treatment failure. Secondary endpoints included time to death, duration of bacteremia, adverse events, in-hospital mortality, and clinical outcome of high-burden diseases.

Cefazolin may be associated with similar rates of clinical cure as oxacillin, 84% vs. 67% cure of high burden infections and 76% vs. 67% successful treatment of infective endocarditis (IE). There were no dosing differences observed in treatment failures of either group. Mortality was observed in one patient in both study groups.

The study team added that the rates of adverse drug events for cefazolin and oxacillin were similar. “More robust studies are recommended to validate our findings,” noted Dr. Nevrekar.