Analysis of urine-specific antibiograms from veterans to guide empiric therapy for suspected urinary tract infection

Urinary tract infection (UTI) is common among patients at Veterans Affairs Medical Centers (VAMCs), many of whom are elderly men with underlying urological problems. Most UTI guidelines address uncomplicated UTI in women, and clinicians may select empiric therapy based on local hospital-wide Escherichia coli cumulative susceptibility (antibiogram) data. To inform selection of empiric therapy for UTI at the Minneapolis VAMC (MVAMC), we compiled antimicrobial susceptibility testing (AST) results for 1 year's urine isolates. We analyzed these AST results (bioMerieux VITEK®) for 2494 microbiologically significant urine isolates at MVAMC from June 2013 through May 2014. For antimicrobial-organism combinations that were not tested, we imputed results based on local or published data and/or expert opinion. For ambiguous antimicrobial-organism combinations, we analyzed susceptibility as both 0% and 100%. We calculated cumulative percent susceptible for 26 relevant antimicrobial agents, overall and stratified by Gram stain characteristic and clinical site. The study population included 1548 Gram-negative and 946 Gram-positive urine isolates. Species distribution varied significantly by clinical site. E. coli represented only 27% of isolates overall (9-37%, depending on site); also prevalent were Enterococcus (14%) and other Gram-positive organisms (23%). Urine-specific antibiograms varied significantly by Gram stain characteristic, between E. coli and other Gram-negative organisms, and by clinical site. Of the oral agents, only fosfomycin provided ≥80% susceptibility. Ultimately, E. coli represented urine isolates poorly with respect to species distribution and AST results. We conclude that urine-specific antibiograms, stratified by Gram stain characteristic and clinical site, may improve empirical UTI therapy for veterans.