Emergence of trimethoprim-resistant enterobacteria in patients receiving long-term co-trimoxazole for the control of intractable urinary-tract infection.

In patients with previously intractable urinary-tract infection treated with low-dose co-trimoxazole for 6--58 (mean 32.7) months, the percentage of infected urines fell from 41.4 before treatment to 6.3 during treatment. Only 6 episodes of infection were due to trimethoprim-resistant bacteria. Results in a small group of patients in whom treatment was continued with trimethoprim alone were similar. Under the conditions of this study, long-term control of urinary-tract infection was not materially compromised by breakthrough infections due to trimethoprim-resistant organisms.