843. Mortality outcomes of cefazolin versus nafcillin for methicillin-sensitive S.aureus blood stream infection: a 4-year prospective cohort study in a Californian tertiary medical center
Session: Poster Abstract Session: Bacteremia and Endocarditis
Friday, October 9, 2015
Room: Poster Hall
Background:  While in-vitro data have indicated possible treatment failure for methicillin-sensitive S.aureus blood stream infection (MSSA BSI) when using cefazolin, recent observational studies have been consistent with possible reduction in mortality in those receiving cefazolin versus nafcillin. We thus examined 90-day mortality differences in those receiving cefazolin compared to nafcillin for MSSA BSI in a safety-net public hospital. Methods:  Participants with MSSA BSI admitted to San Francisco General Hospital Jan 2008 – Dec 2012 were enrolled in a prospective cohort study with clinical, microbiological and sociodemographic data collected, including 90-day mortality confirmed by review of patient records, CDC National Death Index and Social Security Agency master death file. Persons receiving cefazolin or nafcillin as the predominant IV antimicrobial agent were included. Association between receipt of cefazolin and 90-day death was estimated by univariate and then multivariate analysis including a propensity score of receiving cefazolin as the second predictor in a logistic regression model. Results: Of 230 MSSA BSI cases, 30 received nafcillin and 70 received cefazolin as the predominant antimicrobial, and 10/100 died within 90 days. Univariate analysis showed substantive but non-statistically significant reduced odds of death in those receiving cefazolin (OR = 0.38, 95% CI 0.10 -1.44). Multivariate analysis with propensity scores also estimated a large reduction in 90-day mortality in those receiving cefazolin, although this effect was not statistically significant (aOR = 0.40, 95% CI 0.09-1.74, p =0.22). Results were similar with sensitivity analyses. Conclusion:  We found a large reduction in 90-day mortality in those receiving cefazolin compared to nafcillin for MSSA BSI, but this finding was not statistically significant. The magnitude of effect seen in this and other studies justifies further study.
Simon Pollett, MBBS, BMedSci, DTMH, FRACP, Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, CA; Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, Sydney, NSW, Australia, Sanjiv Baxi, MS, MD, MPH, Department of Medicine, The University of California at San Francisco, San Francisco, CA, Peter Bacchetti, PhD, Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, CA and Henry Chambers, MD, FIDSA, Medicine, University of California San Francisco, San Francisco, CA

Disclosures:

S. Pollett, None

S. Baxi, None

P. Bacchetti, None

H. Chambers, Cubist: Grant Investigator , Grant recipient
AstraZeneca: Scientific Advisor , Consulting fee
Pfizer: Scientific Advisor , Consulting fee
Theravance: Scientific Advisor , Consulting fee
Merck: Shareholder , Stock holder
Genentech: Investigator and Scientific Advisor , Consulting fee and Research grant

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