Assessment of Antimicrobial Susceptibility Testing Profiles of Urine Isolates from Veterans to Guide Empiric Therapy for Suspected Urinary Tract Infection

BACKGROUND: Urinary tract infection (UTI) is common among patients at Veterans Affairs Medical Centers (VAMCs), many of whom are elderly men with underlying medical or urological problems. Most UTI treatment guidelines address uncomplicated UTI in women and presume knowledge of local antimicrobial susceptibility testing (AST) patterns for uropathogens, which often are unknown or are inferred from E. coli. To inform selection of empiric therapy for UTI at our VAMC, we compiled AST data for one year’s urine isolates. METHODS: We compiled AST results (bioMerieux VITEK®) for the 2,494 significant urine isolates from the Minneapolis VAMC clinical microbiology laboratory from June 2013 through May 2014. For “drug-bug” combinations that were not tested we imputed results based on local or published data, and/or expert opinion. We then calculated cumulative % susceptible for 25 relevant antimicrobial agents, overall and stratified by Gram stain group and clinical site (intensive care unit, inpatient, outpatient, community residential centers, or extended care). In ambiguous situations susceptibility was analyzed as both 0% and 100%. RESULTS: The 2,494 urine isolates included 946 Gram-positive and 1,548 Gram-negative organisms. Species distribution varied significantly by clinical site. E. coli represented only 27% of isolates overall (9–37%, depending on site). Enterococcus (14%) and other Gram-positives (23%) were also prevalent. Cumulative AST profiles varied significantly (i) by Gram stain group, (ii) between E. coli and other Gram-negatives, and (iii) by clinical site. No tested oral agent provided ≥ 80% overall susceptibility. Although AST data were unavailable for fosfomycin, imputation suggested 82%-95% susceptibility overall. CONCLUSION: Among urine isolates from veterans, E. coli was a minor contributor and a poor surrogate for total population AST profiles. The only oral agent that provided ≥ 80% susceptibility overall was fosfomycin, suggesting that it could be an important option for empiric lower UTI therapy for veterans. Urine isolate-specific antibiograms that reflect local AST data, stratified by Gram stain group and clinical site, could improve empirical UTI therapy for veterans, as could performance of urine Gram stains. DISCLOSURES: J. R. Johnson, Grant Investigator, Grant recipient Merck: Grant Investigator, Grant recipient Tetraphase: Grant Investigator, Grant recipient