Antibacterial activity of ofloxacin in urine during four days after a single oral 400-mg dose

Antibacterial activity of ofloxacin in urine after a single oral dose of 40 0 mg was evaluated in ten healthy female volunteers. Urine was collected ov er six periods, i.e., 0-6h, 6-12h, 12-24h, 24-48h, 48-72h, and 72-96h postd ose. Ofloxacin levels were assayed in all samples using a microbiological m ethod and HPLC. Urinary ofloxacin MICs were determined for five bacterial s trains recovered from urine, two E. coli strains of which one was susceptib le and the other resistant to nalidixic acid (Nal-A), one Klebsiella pneumo niae resistant to nalidixic acid (Nal-B), one Staphylococcus saprophyticus strain, and one Enterococcus faecalis strain; MICs were 0.06, 0.25, 1, 0.25 , and 2 mg/L, respectively. Mean urinary ofloxacin levels by the microbiolo gical method during the six collection periods were 193.3 +/- 30.3, 138.1 /- 31, 53.2 +/- 7.3, 8.3 +/- 0.8, 1.4 +/- 0.2, and 0.6 +/- 0.1 mg/L, respec tively. HPLC provided similar results: 216.7 +/- 31.6, 130.7 +/- 20.5, 56.5 +/- 7.1, 8.3 +/- 0.9, 1.5 +/- 0.3, and 0.5 +/- 0.05 mg/L, respectively. Me an urinary ofloxacin excretion over 96 h was 67.4 +/- 3.6% of the dose by t he microbiological method and 72.5 +/- 2.5% of the dose by HPLC. On the fir st day, bacteriostatic activity of urine against enterobacteria exceeded 32 and was greater than 8192 fur the nalidixic acid-susceptible E. coli strai n; on the next day, overall values were equal or greater than 8 for the nal idixic acid-resistant E. coli and K. pneumoniae strains. Bacteriostatic act ivity was equal to or greater than 32 for the S. saprophyticus strain durin g the first two days and equal to 8 on the first day and 4 on the second da y for the E. faecalis strain.