Prevalence of Esbl-Producing E. Coli in Outpatient Urinary Tract Infections

Abstract

Background: Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli represents an emerging threat to antimicrobial therapy in community-onset urinary tract infections (UTIs). Current prevalence data and risk stratification in outpatient populations remain variable across geographic regions, necessitating systematic epidemiological surveillance to guide empirical treatment decisions.

Methods: A cross-sectional observational study was conducted over 18 months (January 2022–June 2023) among outpatients presenting with acute UTI symptoms at a tertiary care hospital in Jaipur, Rajasthan, India. Consecutive symptomatic patients aged ≥18 years with urinalysis positive for pyuria and/or bacteriuria were enrolled (n=412). Midstream clean-catch urine samples were cultured on MacConkey agar; bacterial identification was performed via VITEK 2 automated system. ESBL production was detected using the phenotypic double-disc synergy test with ceftazidime (30 μg) and clavulanic acid (10 μg) according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Molecular confirmation was conducted via polymerase chain reaction (PCR) targeting blaCTX-M genes. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for ESBL-positive UTI (α=0.05; 95% confidence intervals reported).

Results: Of 412 symptomatic outpatients, 287 (69.7%) yielded culture-positive results with bacterial counts ≥10⁵ CFU/mL. Escherichia coli accounted for 221 (77.0%) of positive isolates. Among E. coli isolates, 71 (32.1%) were phenotypically confirmed as ESBL producers; molecular analysis confirmed blaCTX-M genes in 63 isolates (88.7%), with CTX-M-15 predominating (71.4%). Independent risk factors included prior hospitalization within 6 months (adjusted odds ratio [aOR] 3.18, 95% CI 1.84–5.51, p<0.001), prior cephalosporin exposure (aOR 2.94, 95% CI 1.72–5.03, p<0.001), recurrent UTI history (≥2 episodes/6 months; aOR 2.67, 95% CI 1.51–4.72, p=0.001), and advanced age (≥55 years; aOR 1.89, 95% CI 1.12–3.19, p=0.018). Resistance to fluoroquinolones and trimethoprim-sulfamethoxazole exceeded 75% in ESBL-producers, whereas all isolates remained susceptible to imipenem and meropenem. Clinical cure at day 7 (symptom resolution + negative follow-up culture) was achieved in 94.1% of patients treated with carbapenems versus 71.8% of those receiving empirical fluoroquinolones (p=0.008).

Conclusion: ESBL-producing E. coli accounts for nearly one-third of community-onset UTIs in outpatient populations, with epidemiological patterns reflecting prior healthcare exposure and antimicrobial selection pressures. Targeted screening and carbapenem-based therapy directed by rapid culture and susceptibility testing are warranted in high-risk populations to optimize treatment outcomes and curtail inappropriate antibiotic escalation.