Influence of a prophylactic single dose of ciprofloxacin on the level of resistance of Escherichia coli to fluoroquinolones in urology.

During the years 1991-1996 an increase in fluoroquinolone-resistant Escherichia coli was observed at the Urological Department of the Municipal Hospital in Straubing, Germany. A prospective study was undertaken to investigate the influence of single-dose prophylaxis (SDP) using 500 mg ciprofloxacin orally on the level of resistance to ciprofloxacin of faecal E. coli. One hundred and five patients were recruited to the study: E. coli resistance to ciprofloxacin before prophylaxis was 3% (3/91) in contrast to 12% (5/42) after prophylaxis (P = 0.052). In 31 isolates no major change in the low MIC values before and after SDP was observed. PFGE showed clonal diversity in about half of the cases. Three isolates showed low-level resistance and three isolates high-level resistance to ciprofloxacin both before and after SDP. PFGE showed clonal identity in all cases. All patients had previously been treated with fluoroquinolones (FQ). In two isolates emergence of high-level resistance to ciprofloxacin after SDP occurred. PFGE showed clonal diversity in both cases. We conclude that after SDP with 500 mg ciprofloxacin there is a shift to gram-positive bacteria in the faeces and an increase in the rate of FQ resistance. Since selection of highly resistant E. coli is possible, a careful risk-benefit evaluation of prophylaxis with FQ is indicated.