Evaluation of antibacterial efficacy of drugs for urinary tract infections by genotyping based on pulsed-field gel electrophoresis (PFGE).

Abstract

We attempted to determine whether the same bacterium isolated from patients with urinary tract infections (UTI) before and after treatment with antimicrobial agents was of the same strain ("persisted") or of a different strain ("changed"). Furthermore, to verify the effectiveness of antimicrobial agents for UTI, we investigated whether bacterial strains could be classified as persisted or changed based on their electrophoretic patterns in pulsed-field gel electrophoresis (PFGE). We examined eight species of bacteria ( Enterococcus avium, Staphylococcus epidermidis, Pseudomonas fluorescens, Serratia marcescens, Citrobacter freundii, Enterobacter cloacae, Enterobacter aerogenes, and Escherichia coli), consisting of 41 strains (19 pairs isolated before and after treatment with antimicrobial agents) isolated from patients with complicated UTI. It was concluded that all bacteria were unchanged, based on the clinical effect on bacteriuria. The chromosomal DNA of these bacteria was digested with restriction enzymes and classified based on their electrophoretic pattern in PFGE. A comparison of the patterns of the fragments revealed that 14 pairs were indistinguishable before and after treatment, 3 pairs were closely related, 1 pair was possibly related, and 1 pair was different. These results demonstrated that 18 pairs of isolates (indistinguishable, closely related, and possibly related) were highly likely to be continued infections by the same strain, and that 1 pair (different) had been replaced by another strain. Based on these results, we believe that bacterium genotyping by PFGE is a more effective method for evaluating the antibacterial efficacy of antimicrobial agents.