Laird Harrison

September 10, 2012

September 10, 2012 (San Francisco, California) — Antibiotics work better than cranberries or lactobacilli in preventing recurrent urinary tract infections, 2 new studies show.

"They are more effective, but you have resistance problems," said Suzanne Geerlings, MD, PhD, an infectious disease specialist from the Academic Medical Center in Amsterdam, the Netherlands.

Dr. Geerlings presented the results of 2 studies pitting cranberry tablets and lactobacilli against antibiotics as prophylaxis in women with recurrent urinary tract infections and a meta-analysis of alternatives to antibiotics for the syndrome here at the 52nd Interscience Conference on Antimicrobial Agents and Chemotherapy.

Dr. Geerlings defined "recurrent" as 3 urinary tract infections per year or 2 urinary tract infections in the previous month.

Between 50% and 70% of all women have urinary tract infections in their lifetimes, and 20% to 30% of these women have recurrent infections, she explained.

The infections are particularly common in postmenopausal women. Antibiotics are effective in preventing them, but may be losing their effectiveness as the organisms that cause the infections build up their resistance.

Researchers theorize that reduced estrogen results in less lactobacilli, which creates an increased opportunity for colonization by pathogens, particularly Escherichia coli, she said.

In younger women, sexual intercourse is the primary risk factor, she added.

Some research has showed that a vaginal estrogen cream can reduce the recurrence of urinary tract infections, but some women don't like applying it. That has prompted some researchers to study whether lactobacilli supplements can replace the lactobacilli in the vagina.

Many women use cranberry juice or tablets because fructose and proanthocyanidins can inhibit the adherence of E coli to the uroepithelial cell receptors, said Dr. Geerlings.

She and her colleagues set out to compare these alternatives to antibiotics.

In the first trial, they gave trimethoprim/sulfamethoxazole (TMP/SMX) 480 mg to 127 postmenopausal women with recurrent urinary tract infections for 12 months.

Another 125 matched women took oral capsules containing Lactobacillus rhamnosus GR-1 and L reuteri RC-14 twice daily.

The mean cumulative number of symptomatic urinary tract infections after 12 months was 2.9 with TMP/SMX and 3.3 with lactobacilli. The percentage of women who got urinary tract infections was also slightly higher in the lactobacilli group (P = .02).

This led the researchers to conclude that antibiotics are superior in preventing lactobacilli. However, when they analyzed the E coli in these patients, they found a much higher proportion of resistant organisms in those who took the antibiotics.

They got similar results in a head-to-head prophylaxis trial comparing cranberry tablets with TMP/SMX in a similar population.

After 12 months, the mean number of symptomatic urinary tract infections was 4.0 in the 110 women who took cranberry tablets 500 mg twice daily and 1.8 in the 111 women who took TMP/SMX (P = .02). In addition, 78% of the women taking cranberry tablets had a symptomatic urinary tract infection, as did 71% of the women taking TMP/SMX.

The median time to first infection was 4 months in the cranberry group. However, after 1 month, the researchers found increased resistance rates for trimethoprim, TMP/SMX, amoxicillin, and ciprofloxacin in E coli in the women taking TMP/SMX. It took 3 months for resistance to return to baseline levels.

Antibiotic resistance did not increase in women ingesting cranberries. Dr. Geerlings noted that cranberry therapy "is not very effective, but for some women, it's enough."

Looking at the literature on alternatives to antibiotics. Dr. Geerlings reported that there is not much evidence for vitamin C, despite its popularity.

A more promising substance is OM-89 (Uro-Vaxom), an oral immunostimulant made with bacterial lysates derived from E coli strains, said Dr. Geerlings. OM-89 were more potent than placebo in small clinical trials, but Dr. Geerlings does not know whether larger trials are underway.

Session moderator Lindsay E. Nicolle, MD, from the University of Manitoba in Winnipeg, Canada, agrees that cranberries do not appear promising as a treatment. She pointed out that other recent trials had negative results.

Dr. Nicolle and Dr. Geerlings have disclosed no relevant financial relationships.

52nd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Abstract 542. Presented September 10, 2012.