Antibiotics prevent more UTIs than cranberries, but resistance is a problem

August 4, 2011

Antibiotic therapy prevented urinary tract infections in women more effectively than cranberry capsules but it also raised resistance to the drugs, a Dutch study reports.

Antibiotic therapy prevented urinary tract infections in women more effectively than cranberry capsules but it also raised resistance to the drugs, a Dutch study reports.

The study, published online July 25 in the Archives of Internal Medicine, randomly assigned 221 premenopausal women who had had at least 3 UTIs in the previous year to a daily regimen of either 1 trimethoprim-sulfamethoxazole (TMP-SMX) 480 mg or cranberry capsules 500 mg twice daily. After 1 year, women taking TMP-SMX reported 1.8 UTIs, compared with 4 UTIs in the cranberry group. New infections occurred at an average of 8 months after starting the antibiotic and 4 months after starting cranberry capsules. Previous studies suggested a potential benefit for cranberry juice or extract without significant side effects.

Resistance to TMP-SMX-as well as trimethoprim, amoxicillin, and ciprofloxacin-increased in the antibiotic group within 1 month. Resistance levels returned to normal 3 months after women discontinued the antibiotic.

“From clinical practice and during the recruitment phase of this study, we learned that many women are afraid of contracting drug-resistant bacteria using long-term antibiotic prophylaxis and preferred either no or nonantibiotic prophylaxis,” the authors write. “In those women, cranberry prophylaxis may be a useful alternative despite its lower effectiveness.”

The researchers report that the increase in resistance among women taking TMP-SMX was “considerable”: 86.3% of Escherichia coli isolates from indigenous fecal flora were resistant to the drug after 1 month. Resistance to amoxicillin and fluoroquinolones increased simultaneously.