Interpretation of the bacteriologic outcome of antibiotic treatment for uncomplicated cystitis: impact of the definition of significant bacteriuria in a comparison of ritipenem acoxil with norfloxacin. Swedish Urinary Tract Infection Study Group.

The efficacy and safety of a 5-day course of treatment with the new oral penem agent ritipenem acoxil (500 mg three times daily) or with norfloxacin (200 mg twice daily) were assessed in a double-blind study of women with uncomplicated cystitis. The effects of the definition of bacteriuria used on the interpretation of treatment outcome were also analyzed. Of 281 women randomized to one of the two treatment arms, 84% were evaluable in terms of the bacteriologic efficacy of therapy; 99% of the evaluable patients returned for the first follow-up examination and 92% for the second. Five to 9 days after the completion of therapy, persistent bacteriuria was documented in more women given ritipenem acoxil than norfloxacin (95% confidence interval, 0.14; 0.38). The two groups did not differ markedly with regard to bacteriologic or clinical outcome 3 to 4 weeks after treatment. Subanalyses of bacteriologic outcome showed that failure rates varied between 6% and 67% for ritipenem acoxil and between 1% and 43% for norfloxacin, depending on how significant posttherapy bacteriuria was defined; systematic studies are are clearly needed on how best to define significant posttherapy bacteriuria. Ritipenem acoxil caused significantly more adverse reactions (especially diarrhea or loose stools) than norfloxacin (P < .005).