Bacteria Interference May Prevent Urinary Tract Infections

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Rabih Darouiche, MD
Rabih Darouiche, MD

SAN FRANCISCO—Bacterial interference may be an effective way to prevent symptomatic urinary tract infections (UTIs) in patients with neurogenic bladders, according to findings presented here at the 2009 Interscience Conference on Antimicrobial Agents and Chemotherapy.

“We think this is a promising approach,” said lead investigator Rabih Darouiche, MD, Professor of Medicine at Baylor College of Medicine in Houston. “Urinary tract infections in this population are the most common infectious cause for admission to the hospital.  So it is a major problem, and so far there has been no proven approach that would effectively and safely prevent UTI in these patients.”

In a prospective, randomized, placebo-controlled, double-blind, multicenter trial, he and his colleagues investigated the efficacy of instillation of Escherichia coli HU2117, a non-pathogenic strain, into the neurogenic bladder of adult patients with spinal cord injury (SCI) who had a history of recurrent UTIs.

They randomized patients to receive either the E. coli or sterile saline through a newly inserted bladder catheter. The investigators obtained urine cultures weekly during the first four weeks, then monthly thereafter. The patients were followed up for the occurrence of symptomatic UTI for a period of 12 months. The patients in both arms of the study had similar characteristics.

The group that received the bacterial interference consisted of 17 men (nine quadriplegics and eight paraplegics). The control group included 10 men (six quadriplegics and four paraplegics). Both groups had a mean 4.4 UTIs in the previous year. All patients were  catheterized.

During the 12-month study period, one or more UTIs developed in five (29%) of the 17 patients in the experimental group compared with seven (70%) of the 10 controls. In addition, the average number of UTI episodes per patient-year was lower in the treated group than in the control group (0.05 vs. 1.68). None of the patients developed UTI due to E. coli HU2117 and none had clinical evidence of septicemia following bladder instillations.

Overall, the investigators concluded that there was a greater than two-fold reduction (29% versus 70%) in the likelihood of developing symptomatic UTI in colonized versus non-colonized patients and that these findings surpassed the magnitude of protection afforded by other potentially preventive approaches. 

Dr. Darouiche noted that long-term use of systemic antibiotic prophylaxis in patients with SCI tends to only achieve a modest protection at the expense of an increase in antimicrobial resistance and adverse drug reactions.

He and his colleagues have been working on this approach for more than 12 years. Still, the exact mechanism by which E. coli HU2117 exerts its protective impact is unclear. It may be that this bacterial strain blocks binding sites on the uroepithelium.

Another possibility is that E. coli HU2117 stimulates secretion of substances that kill or inhibit growth of other pathogens. It is also theorized that bacterial interference with this E. coli strain may alter the nutritional or pH level in the surrounding milieu.

Another unknown, Dr. Darouiche said, is whether bacterial interference could be applied to patient populations without neurogenic bladders.

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