This site is intended for health professionals only

Antibiotics more effective than cranberries for preventing UTIs – but raise resistance

Prescribing antibiotics is more effective for the prevention of urinary tract infections in younger women than cranberry extract – but at the expense of emerging antibiotic resistance, according to the results of a randomised controlled trial.

Dutch researchers randomised 221 premenopausal women with recurrent UTIs to either 12-month prophylaxis with  trimethoprim in combination with sulfamethoxazole, at 480mg once daily, or 500mg cranberry capsules twice daily.

After 12 months, the mean number of asymptomatic UTIs was higher in the cranberry group, at 4.0, than the antibiotic group at 1.8.

The proportion of patients with at least one clinical recurrence of symptomatic UTI was higher in the cranberry than in the antibiotic group, at 78% compared with 71%.

Both differences were statistically significant, but there was no significant difference in the number or proportion of patients with microbiologically confirmed symptomatic UTIs, and the differences did not reach significance when measured in the three months of treatment.

But the improvements in clinically diagnosed recurrences of UTI were ‘at the expense' of growing resistance to trimethoprim-sulfamethoxazole and other antibiotics, the researchers said.

After one month, in the cranberry group, 24% of faecal and 28% of asymptomatic urine E. coli isolates were resistant to trimethoprim-sulfamethoxazole, whereas in the antibiotic-treated group, 86% of faecal and 91% of asymptomatic urine isolates of E. coli were found to be resistant.

The researchers also found increased resistance rates for trimethoprim, amoxicillin and ciprofloxacin in the trimethprim-treated group.

Dr Mariëlle Beerepoot, a resident in internal medicine at the Academic Medical Center in Amsterdam, concluded: ‘In premenopausal women with recurrent UTIs, trimethoprim-sulfamethoxazole 480mg once daily, is more effective than cranberry capsules, 500 mg twice daily, for the prevention of recurrent UTIs. However, this should be weighed against the greater development of antibiotic resistance.'

‘Many women are afraid of contracting drug-resistant bacteria using long-term antibiotic prophylaxis and preferred either no or non-antibiotic prophylaxis. In those women, cranberry prophylaxis may be a useful alternative despite its lower effectiveness.'

Arch Int Med 2011; 171: 1270-1278