The carriage of Escherichia coli on the peri-urethral area and in the feces in patients on long term low dose cotrimoxazole therapy.

Peri-urethral and fecal carriage of E. coli has been studied in 30 patients maintained on long term low dose cotrimoxazole and in abacteriuric subjects not receiving any antibiotic. Cotrimoxazole treatment is associated with a dramatic reduction in E. coli carriage both in the feces and especially on the peri-urethral area which persists over months or years. Recovery of trimethoprim-resistant E. coli from the feces was uncommon but when observed antedated subsequent relapse due to resistant organisms. Possible mechanisms for low peri-urethral carriage rates include reduction in fecal carriage, vaginal secretion of trimethoprim or low urinary concentrations of that drug.