Background: Long-term antibiotic therapy is regularly used for children with urinary tract infections (UTIs) to prevent renal damage. Several randomized trials have recently cast doubt on this practice, but none of these trials were placebo controlled. Craig and colleagues conducted the Prevention of Recurrent Urinary Tract Infection in Children with Vesicoureteric Reflux and Normal Renal Tracts (PRIVENT) trial to study the effect of long-term antibiotic treatment on preventing recurrent UTIs in children.

The Study: The authors recruited children from birth to 18 years of age who had at least one symptomatic UTI confirmed by positive urine culture. Children were randomized to receive a daily dosage of placebo or trimethoprim/sulfamethoxazole (TMP/SMX; Bactrim, Septra) at 2 mg of TMP plus 10 mg of SMX per kg, or a suspension containing 40 mg of TMP plus 200 mg of SMX per 5 mL, at 0.25 mL per kg. Each dose was calculated by body weight, and children were monitored for the development of clinically apparent UTIs for one year. The primary outcome was symptomatic UTI and a positive urine culture. Children were excluded from the trial if they had a known contraindication to TMP/SMX, or a known neurologic or urologic cause for UTIs other than vesicoureteral reflux.

Results: The authors followed 564 children with a median age of 14 months at study initiation. Forty-two percent of patients had known vesicoureteral reflux, with 53 percent having at least grade III reflux. The groups did not differ in treatment adherence rates or in baseline traits, including the presence or severity of reflux.

Children in the antibiotic group were less likely to develop a symptomatic UTI than those in the placebo group (13 versus 19 percent, respectively; hazard ratio [HR] = 0.61), resulting in a number needed to treat of 14 to prevent one UTI. Febrile UTIs were also less common in the antibiotic group (7 versus 13 percent, respectively; HR = 0.49). Seventy-five percent of all UTIs occurred within the first six months of the study. No differences in UTI recurrence were evident between groups with regard to age, sex, reflux status, or previous number of UTIs.

Conclusion: The authors conclude that long-term, low-dose antibiotic use is associated with a decrease in the risk of symptomatic UTI in predisposed children. The greatest benefit of antibiotic therapy occurs during the first six months of treatment, when recurrent infection is most likely to happen. In children with a single symptomatic UTI, the authors recommend that TMP/SMX prophylaxis be considered, but not routinely recommended.