A probiotic medication has been shown to reduce the risk of recurrent urinary tract infections by nearly half – making it comparable to a prophylactic course of antibiotics, the current standard treatment for recurrent urinary tract infections.
Concerns about increasing resistance to commonly used antimicrobials such as trimethoprim-sulfamethoxazole and fluoroquinolones has led to a search for alternative means to prevent urinary tract infections (UTIs), with recent investigations focusing on hydrogen peroxide-producing strains of lactobacilli.
These lactobacilli comprise the dominant vaginal flora, competing with and regulating other urogenital microbes, including the harmful Escherichia coli. Women with recurrent UTIs have been shown to typically have depletion of vaginal lactobacilli at the time of their E. coli infections (J. Infect. Dis. 1998;178:446-50).
The new findings, from a randomized, placebo-controlled trial of a vaginal suppository containing Lactobacillus crispatus in 100 young women, were published online April 15 in Clinical Infectious Diseases (Clin. Infect. Dis. 2011;52:1212-17).
For their research, Dr. Ann E. Stapleton of the University of Washington in Seattle, and her colleagues, recruited women with current cystitis and histories of recurrent UTI to be randomized to Lactin-V (Osel Inc., Mountain View, Calif.), a product containing L. crispatus, or placebo. The women (median age 21, median number of UTIs before study 4.5) applied either Lactin-V or placebo daily for 5 days, then once weekly for 10 weeks. Participants were seen in scheduled follow-up visits at 1 week (visit 3) and 10 weeks (visit 4) after beginning Lactin-V or placebo and for symptomatic UTIs. Investigators collected urine samples for culture and vaginal swabs to assess the level of colonization of L. crispatus. Of the 50 women randomized in each group, 48 were entered into analysis.
Recurrent culture-confirmed UTI occurred in 7 of 48 women (15%) receiving Lactin-V, compared with 13 of 48 women (27%) receiving placebo (RR 0.5; 95% confidence interval, 0.2-1.2).
The investigators named as one of the strengths of the study the quantitative molecular method used to assess vaginal flora following UTI, which afforded them a more precise picture of changes in the balance of vaginal microbiota than seen in previous trials.
The investigators also noted that high-level vaginal colonization with L. crispatus throughout follow-up was associated with a significant reduction in recurrent UTI only for women using the suppositories. In their analysis, Dr. Stapleton and colleagues called this finding "striking" and hypothesized that the use of Lactin-V "confers a significant advantage over repopulation of the vaginal microbiota with endogenous L. crispatus," and that the L. crispatus isolate used in the intervention offered "unique properties for protection" over the natural recolonization process.
The investigators did not compare Lactin-V to prophylactic antibiotics in their study. However, they noted that a meta-analysis of 10 randomized controlled trials evaluating continuous antimicrobial prophylaxis (Clin. Evid. [Online] 2008 Jul 17;2008. pii:0801) found rates of rates of recurrent UTI reduced to 12% (24 of 195 participants) compared with 65% (116 of 177 participants) among placebo recipients, "with a [relative risk] of rUTI that is very comparable to our findings (RR, 0.21; 95% CI, 0.13-0.33)."
Dr. Stapleton and colleagues concluded that "[t]his antimicrobial-sparing, well-tolerated intervention compares favorably with historical data regarding antimicrobial prophylaxis, the current standard of care for the prevention of rUTI."
The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases, and the Office of Research in Women’s Health, National Institutes of Health; Dr. Stapleton and her coauthors said they had no relevant financial disclosures.