Antibiotic Exposure and Risk of MDR Urinary Tract Infections: A Case-Control Study

Background

Antimicrobial resistance (AMR) is a critical global health threat. Antibiotic consumption is a key modifiable risk factor for multidrug-resistant (MDR) infections, yet its magnitude across healthcare settings remains poorly characterised.

Objectives

To estimate the association between antibiotic consumption and MDR urinary tract infection (UTI) development, assess the impact of increasing antibiotic diversity, and characterise resistance patterns across healthcare settings.

Methods

Observational case-control study using laboratory and clinical data from a tertiary care hospital (2023). Cases were urine samples with MDR isolates; controls had susceptible isolates. Exposure was defined as systemic antibiotic use within the prior 12 months. Odds ratios (OR) and binary logistic regression were used to estimate crude and adjusted associations.

Results

We included 351 cases and 790 controls (median age 75; 74% female). Prior antibiotic use was associated with MDR UTI development (adjusted OR 2.30; 95% CI 1.63–3.23). Increasing antibiotic diversity (number of antibiotic classes used) was independently associated with MDR UTIs, with a 40% risk increase per additional class (OR 1.40; 95% CI 1.29–1.51). Associations between consumption of twelve antibiotic classes and MDR UTI development were identified, and six remained significant in multivariate analysis: carbapenems, third-generation cephalosporins, lipopeptides, oxazolidinones, β‑lactam/β‑lactamase inhibitor, and sulfonamides. Resistance patterns differed significantly between community and hospital-acquired infections (p < 0.001), with ESBL-producing E. coli predominating in both community (67.6%) and hospital settings (26.9%).

Conclusions

Exposure to carbapenems, third‑generation cephalosporins, and β‑lactam/β‑lactamase inhibitor combinations most strongly increased MDR UTI risk. Cumulative effects and distinct resistance patterns support targeted restrictions and setting‑specific stewardship policies.

Key messages

• Our study reveals that increasing antibiotic diversity significantly drives MDR UTI risk. We advocate for targeted stewardship to limit high-impact antibiotic combinations.

• Resistance patterns vary sharply between community and hospital settings. Our findings highlight the need for setting-specific policies to curb the rise of carbapenem-resistant infections.