Epidemiology of urinary tract infections caused by extended-spectrum beta-lactamase-producing Escherichia coli.

Objectives: To describe the epidemiology of urinary tract infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli.

Methods: We performed three studies: a trend study (1999 to 2004) to assess the evolution and origin of ESBL-producing E. coli isolates from urine samples; a comparison of the susceptibility patterns of ESBL-producing E. coli and a random sample of non-ESBL-producing E. coli isolated in the same interval, and a retrospective chart review to determine the risk factors for acquisition of, and outcomes from, urinary tract infections caused by ESBL-producing E. coli (n = 61) compared with a random sample of non-ESBL-producing E. coli urinary tract infections (n = 61) from patients attending our institution and matched by temporal occurrence.

Results: ESBL-producing E. coli significantly increased from 2 (0.20%) to 89 (5.52%) isolates per year (P value for trend = 0.000). Of the 161 patients with urinary tract infections caused by ESBL-producing E. coli, 100 (62%) were attending ambulatory health centers, and 61 (38%) were attending the hospital. ESBL-producing E. coli showed a significant reduction in the susceptibility to most antimicrobials, although carbapenems and fosfomycin retained significant activity. The chart review study showed that previous treatment with fluoroquinolones (odds ratio 12.98, 95% confidence interval 1.81 to 106.51, P = 0.017) and the presence of a urinary catheter (odds ratio 2.64, 95% confidence interval 1.01 to 6.88, P = 0.047) were independent risk factors associated with infections caused by ESBL-producing E. coli.

Conclusions: ESBL-producing E. coli is a problem of increasing importance. Our study results may help physicians select appropriate antimicrobial therapy in patients suspected of having urinary tract infections caused by ESBL-producing E. coli.