Journal Club: Does antibiotic prophylaxis prevent recurrent urinary tract infections?

A recent study demonstrated that long-term, low-dose trimethoprim-sulfamethoxazole (TMP-SMX) was associated with a modest decrease in urinary tract infections (UTIs) in children who had had at least 1 such symptomatic infection in the past. The study was conducted in 576 youngsters from birth to 18 years of age recruited from 9 centers in Australia; median age was 14 months.

After a 2-week run-in period during which all children received TMP-SMX, half the participants continued the drug and half were given placebo. The children were seen at 3-month intervals, when the study drug was dispensed, during the 12-month follow-up. The single daily dose was calculated by volume according to body weight (2 mg of TMP plus 10 mg of SMX per kilogram).

During the study period, UTI was diagnosed in 13% of patients in the antibiotic group and in 19% in the placebo group. At 12 months, 14 patients therefore would need to have been treated to prevent 1 UTI. Escherichia coli was the chief causative bacterium in both groups-responsible for 83% of infections among antibiotic recipients and 84% of infections among placebo recipients. The findings were not significantly affected by variables such as age, sex, urinary reflux status, and number of previous UTIs (Craig JC, et al. N Engl J Med. 2009;361[18]:1748-1759).

This study offers faint praise for antibiotic prophylaxis in UTIs. Fourteen person-years of antibiotics seem like a high price to pay to prevent 1 UTI, especially when the price includes medication cost, medication side effects, and antibiotic resistance. This study included children with all grades of urinary reflux and those with recurrent infection. Perhaps ongoing studies will define a more limited population for which the benefit of prophylaxis warrants all the costs.-MB