Isolation of fluoroquinolone-resistant rectal Escherichia coli after treatment of acute uncomplicated cystitis

Objectives: Given increasing rates of co-trimoxazole resistance among uropathogens causing acute uncomplicated cystitis, fluoroquinolones, nitrofurantoin and fosfomycin are often considered as alternative empirical therapy. The choice between these drugs should depend in part on whether they are associated with the isolation of drug-resistant microbial flora. We conducted a randomized treatment trial to assess the effects of ciprofloxacin, nitrofurantoin and fosfomycin on the rectal microbial flora of women with acute uncomplicated cystitis, including isolation of fluoroquinolone-resistant strains. Methods: Pre-menopausal women presenting with acute uncomplicated cystitis were randomized to treatment with 3 days of ciprofloxacin, 7 days of nitrofurantoin, or a single dose of fosfomycin. Women were followed for 1 month for evaluation of clinical and microbiological responses as well as for isolation of resistant rectal E. coli. Results: Sixty-two women (25 ciprofloxacin, 17 nitrofurantoin, 20 fosfomycin) were enrolled and eligible for analysis. All three regimens were well tolerated and resulted in > 90% clinical and bacteriological cure. The prevalence of rectal E. coli was markedly decreased by ciprofloxacin and fosfomycin, but not by nitrofurantoin. One woman treated with ciprofloxacin had emergence of two ciprofloxacin-resistant rectal E. coli strains within 10 days of completing therapy. No emergence of resistance was observed in the other two treatment groups. Conclusions: This study demonstrates that fluoroquinolone-resistant E. coli remain infrequent in the rectal flora of women with uncomplicated cystitis in Seattle. However, a 3 day course of a fluoroquinolone for treatment of uncomplicated cystitis was followed by isolation of fluoroquinolone-resistant rectal E. coli in one patient.