Bacterial resistance patterns and associated factors in pediatric urinary tract infections: A susceptibility profile analysis

Introduction: Pediatric urinary tract infections (UTIs) represent an important reservoir of antimicrobial- resistant pathogens, predominantly Escherichia coli, with limited regional data on susceptibility patterns and factors associated with resistance. Antimicrobial resistance may be intrinsic or acquired; in this context, broad-spectrum β-lactamases (BLEA; classical β- lactamases conferring resistance to penicillins and early-generation cephalosporins) and extended-spectrum β-lactamases (ESBL; enzymes hydrolyzing extended-spectrum cephalosporins) were the predominant resistance mechanisms, the latter contributing to multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) phenotypes. Increasing global rates of ESBL-producing Enterobacterales have been reported, with pediatric prevalence reaching 14% worldwide and rising substantially over time. Resistance mechanisms, including ESBL, AmpC, and carbapenemases, compromise empirical therapy and limit oral treatment options. Regional variability and associations with prior antibiotic exposure and urinary tract abnormalities highlight the need for local susceptibility data to guide antimicrobial stewardship in pediatric UTIs.

Methods: An analytical multicenter cross-sectional study was conducted in three healthcare institutions in Colombia. Children aged 1 month to 12 years presenting to emergency departments or hospitalized pediatric services with urinary tract infection confirmed by urine culture were included. Significant bacteriuria was defined according to collection method and established colony count thresholds. Patients with contaminated samples, fungal isolates, oncologic disease, organ transplantation, pregnancy, or recurrent UTIs were excluded. Non-probabilistic sampling was used. Antimicrobial susceptibility testing was performed using automated systems following Clinical and Laboratory Standards Institute (CLSI) guidelines. Selection and confounding biases were minimized through homogeneous inclusion criteria, standardized microbiological procedures, verification of covariate overlap, and adjusted statistical analyses to evaluate factors associated with antimicrobial resistance.

Results: 87 children with culture-confirmed UTI were included, with a mean age of 2.21 years; 69% were male. The overall prevalence of bacterial resistance was 82.75% (95% CI: 0.73–0.90). The most frequently isolated resistant pathogens were Escherichia coli (83.3%), Proteus mirabilis (6.9%), and Pseudomonas aeruginosa (1.38%). Resistance was significantly more frequent in E. coli infections compared with other pathogens (80.9% vs. 63.2%). The most frequent resistance mechanisms were broad-spectrum β-lactamases (BLEA/BSBL) (41.6%), penicillinase production (26.4%), extended-spectrum β-lactamases (ESBL) (15.3%), AmpC (8.3%), and inhibitor-resistant TEM (IRT) (8.3%). Among E. coli isolates, BLEA predominated (48.3%), followed by penicillinase (23.3%) and BLEE (16.7%). After adjustment using Poisson regression with robust variance, the adjusted prevalence of bacterial resistance in E. coli isolates was 81.2% (95% CI: 0.72–0.89). Risk of malnutrition (p = 0.023), urinary tract manipulation within the previous three months (p = 0.042), hospitalization during the last six months (p = 0.040), and patient age (p = 0.0486) were significantly associated with bacterial resistance.

Conclusion: Antimicrobial resistance in pediatric UTI was highly prevalent across the evaluated centers, with widespread circulation of resistant pathogens. Malnutrition risk, recent urinary tract manipulation, hospitalization, and patient age significantly associated with resistance. Characterizing local etiological agents and susceptibility patterns provides essential, context- specific evidence to guide empirical antibiotic selection, optimize early clinical decision- making, and strengthen antimicrobial stewardship strategies. Tailoring therapeutic approaches to local resistance profiles is critical to improving the quality and safety of pediatric care and mitigating the further emergence of antimicrobial resistance.