Low dose trimethoprim prophylaxis in long term control of chronic recurrent urinary tract infection

26 patients with chronic urinary tract infections (UTI) were treated with 1 tablet of 100 mg trimethoprim (TMP) once daily for up to 6 months as long term prophylaxis. The recurrence rate before prophylaxis was 26/100 months, compared to a significantly lower frequency (3.3 recurrences/100 months, p less than 0.001) during prophylaxis. The post-prophylactic rate returned to the pre-prophylaxis rate: 23 recurrences/100 months. All Escherichia coli strains causing post-prophylactic UTI were TMP sensitive. The number of rectal enterobacteria were markedly reduced during prophylaxis (p less than 0.05). A 10% recovery of TMP resistant enterobacteria from rectal swabs was noted early (less than or equal to 1 month) during prophylaxis, but no significant further accumulation occurred.