Recurrent UTIs caused by original E coli strain

Washington-A majority of recurrent urinary tract infections in women are caused by Escherichia coli bacterial persistence or reinfection with the originally infecting E coli strain, according to findings from a Danish study presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy.

"Our findings are in accordance with the current predominant theory of the gastrointestinal tract being a reservoir for E coli that cause urinary tract infections," said Karen Ejrnaes, PhD, department of antimicrobials and infection control, Statens Serum Institut, Copenhagen.

"But [our findings] could also support the recent discovery that E coli is able to persist intracellularly in the bladder epithelium, despite appropriate antibiotic treatment, constituting a reservoir for urinary tract infection.

Urinary tract infections are one of the most common bacterial infections of any organ system and account for a significant morbidity and high medical costs, Dr. Ejrnaes explained. Recurrent UTIs are also common, with 16% to 40% of women who have an episode of UTI developing recurrence.

High incidence of recurrenceConsidering the high incidence of recurrent UTIs, it is important to understand the pathogenesis behind them in order to devise new treatment and preventive strategies in the future, Dr. Ejrnaes said.

To that end, Dr. Ejrnaes and colleagues randomly selected 156 women with UTI caused by E coli at the index episode and with E coli at follow-up. All of the subjects were drawn from a private practice population of 1,143 women with community-acquired lower UTIs.

The women were enrolled in a multicenter, double-blind, placebo-controlled comparative study of different dosing regimens of the antibiotic pivmecillinam, a penicillin derivative not available in the United States: 200 mg, three times daily for 7 days; 200 mg, twice daily for 7 days; 400 mg, twice daily for 3 days, or placebo.

Bacterial evaluationsClinical and bacterial evaluations were performed at day 1; day 8 to 10 at first follow-up; and day 35 to 49 at second follow-up. The original infecting E coli strains and the E coli strains from follow-up underwent typing with pulsed-field gel electrophoresis to differentiate whether recurrent UTI was caused by a strain identical to the original infecting strain or whether the recurrent UTI was caused by a completely new strain.

In 154 evaluable patients, 133 patients (86%) with recurrent UTIs at follow-up were infected with an E coli strain identical to the primary infecting strain. In the active antibiotic treatment group, 46 of 60 reinfections (77%) and 34 of 40 cases of bacterial persistence (85%) were due to an E coli strain identical to the original strain, according to Dr. Ejrnaes. In the placebo group, 53 of 54 (98%) of all recurrent UTIs were due to a strain identical to the originally infecting strain, Dr. Ejrnaes reported.