GENETIC-EVIDENCE SUPPORTING THE FECAL-PERINEAL-URETHRAL HYPOTHESIS INCYSTITIS CAUSED BY ESCHERICHIA-COLI

Purpose: The fecal-perineal-urethral hypothesis to explain the cause o f urinary tract infections (UTI) by enteric bacteria has been supporte d by longitudinal studies using methods of serotyping and detecting ur ovirulence factors such as P fimbriae. However, genetic techniques to more accurately characterize Escherichia coli strains have not been ex ploited. Materials and Methods: A total of 2,700 E. coli colonies isol ated from the urine and rectal swabs of 9 female subjects with acute u ncomplicated cystitis and from the rectal swabs of 30 healthy women we re serotyped and examined for genes encoding various urovirulence fact ors by colony hybridization test. The clonality of the urine and fecal isolates of E. coli from the cystitis subjects was further evaluated by pulsed-field gel electrophoresis (PFGE). Results: E. coli strains c ausing cystitis dominated the rectal flora of 7 of 9 patients. In the remaining 2 patients, similar clones comprised at least 20% of the fec al flora. Carriage of E. coli strains with a variety of urovirulence f actors was quite common among healthy women. PFGE demonstrated that mo st of the isolates sharing the same serotypic characteristics and viru lence factors in the urine and rectal swab samples from each subject w ere identical. Conclusions: Based upon precise genetic techniques, our results clearly support the fecal-perineal-urethral hypothesis, indic ating that E. coli strains residing in the rectal flora serve as a res ervoir for urinary tract infections, e.g., cystitis.