Trimethoprim-sulfamethoxazole and trimethoprim alone in the prophylaxis of childhood urinary tract infection.

In 1975 trimethoprim-sulfamethoxazole (TMP-SMZ) was found effective in the prophylaxis of childhood urinary tract infection. The rate of recurrence in 130 children who received prophylaxis was only 0.05 infections per year. No fecal coliforms were found in 70% of rectal swabs, and only 10% of the isolates of coliform organisms were resistant to TMP. During effective, low-dose urinary prophylaxis with TMP-SMZ in 130 children for periods of two to 10 years, no effects of the drug on hematologic or renal function were observed, and somatic growth was normal. However, the frequency of resistance to TMP among fecal coliforms increased from less than 10% in 1970-1975 to 34% in 1980. This increase was not related to the duration of prophylaxis and appeared to represent a secular increase in TMP resistance among coliforms. TMP alone also was effective in urinary prophylaxis; only three of 39 children experienced a recurrence of urinary tract infection during a total of 309 months of prophylaxis in 1978-1980. The effect of TMP prophylaxis on the bowel flora was similar to that of TMP-SMZ prophylaxis. Resistance to TMP was found in 16% of isolates from rectal swabs from children receiving TMP alone.