Can urinary nitrite results be used to guide antimicrobial choice for urinary tract infection?

Enterococcus is unable to reduce nitrates and is also considered clinically resistant to trimethoprim/sulfamethoxazole (TMP/SMX), the drug of choice for uncomplicated urinary tract infection (UTI). The purpose of this study was to determine whether urinalysis nitrite results can be used to guide antimicrobial therapy when treating UTI in the emergency department (ED). A retrospective chart review examined 159 university hospital ED outpatients who had signs or symptoms of UTI and had a urinalysis with positive culture. Patients were categorized into two groups based on nitrite results. The proportion of isolates sensitive to TMP/SMX in each group was compared by using a two-sample z-test. Eighty-six urinalyses were nitrite positive: 67 (78%) contained TMP/SMX-sensitive isolates. Seventy-three urinalyses were nitrite negative; 60 (82%) contained sensitive isolates. There was no statistically significant difference in the proportion of isolates sensitive to TMP/SMX. Thus, we conclude that emergency physicians should not adjust antibiotic therapy for UTI based on nitrite results.