Rate and Predictors of Urine Culture Positivity Following Single-Dose Antibiotic Administration: a Prospective...

International guidelines advocate obtaining urine cultures prior to antibiotic administration in hospitalized patients with suspected urinary tract infection (UTI). However, adherence remains suboptimal. The aim of this study was to evaluate the positivity rate of urine cultures following a single empiric antibiotic dose and to identify factors associated with post-antibiotic culture positivity.

A prospective observational study was conducted in an internal medicine ward between December 2019 and June 2024. Patients diagnosed with UTI who had both pre- and post-antibiotic urine cultures were included. Positivity rates of post-antibiotic urine cultures were assessed. Factors associated with culture positivity were examined using logistic regression.

A total of 132 patients were included in the analysis (59% female; median age 79 years). Eighty-eight patients (67%) had a positive post-antibiotic urine culture. The positivity rate in patients with a sensitive and resistant uropathogen to the empirically administrated antibiotic was 58% and 100%, respectively. Independent predictors for urine culture positivity included older age (adjusted odds ratio [aOR] 1.04, confidence interval [CI] 1.01-1.07, p = 0.007) and recent urinary catheter use in the last 30 days (aOR 14.7, CI 1.66-128, p = 0.016). Culture sampling more than 9 h after antibiotic administration was a negative predictor for culture positivity (aOR 0.41, CI 0.18-0.96, p = 0.041).

Urine culture positivity remains high after a single antibiotic dose in hospitalized patients with UTI. In cases where pre-antibiotic urine cultures are missed, a timely post-antibiotic urine sampling remains clinically relevant for pathogen identification and appropriate antibiotic selection.