Evolving Landscape in Urinary Pathogens and Antimicrobial Susceptibility over Five Years: A Retrospective Observational Study

Abstract

Introduction: Urinary Tract Infections (UTIs) are among the most common bacterial infections in both community and hospital settings. The rising burden of antimicrobial resistance among uropathogens poses a challenge to empirical therapy, particularly in resource-limited settings. Continuous regional surveillance is essential to guide effective treatment strategies. Aim: To evaluate the changing spectrum of urinary pathogens and their antimicrobial susceptibility patterns through analysis of urine culture isolates. Materials and Methods: This retrospective observational study was conducted in the Department of Microbiology, Byramjee Jeejeebhoy Government Medical College and Sassoon General Hospital, Pune, Maharashtra, India from January 2020 to December 2024 on urine culture samples. All outpatients and inpatients presenting to the hospital during the study period with suspected UTI, based on urine culture findings, were included. Semiquantitative culture on Cystine-LactoseElectrolyte-Deficient (CLED) agar was used to isolate significant bacteriuria (≥105 Colony-Forming Units (CFU)/mL), followed by Gram staining, biochemical identification and Kirby-Bauer disc diffusion antibiotic susceptibility testing. Demographic parameters, seasonal patterns, and antimicrobial resistance data were analysed. Negative binomial regression and the Cochran-Armitage trend test were applied as appropriate. A p-value of <0.05 was considered statistically significant. Results: A total of 26,045 urine samples were processed, of which 4,248 (16.33%) showed substantial bacterial growth. Of culture-positive cases, 2,219 (52.2%) were females. Most positive cultures were from inpatient settings, 3,466 (81.6%), followed by intensive care units, 417 (9.8%), and Outpatient Departments (OPD), 365 (8.6%). The highest incidence of positive cultures was in the 19-30 years age group, at 835 (19.7%). The lowest incidence was observed in the 13-18 years age group, at 116 (2.7%). E. coli was the most common uropathogen, 1834 (43.2%), followed by K. pneumoniae, 876 (20.6%), and Enterococcus spp. 891 (21.0%). High resistance was recorded among E. coli isolates to ampicillin 1680 (92.3%), cefotaxime 1656 (91.9%), and ceftriaxone 1606 (89.6%). High resistance was observed among Enterococcus spp. to ciprofloxacin 523 (78.2%) and norfloxacin 410 (77.7%). Nitrofurantoin demonstrated lower resistance than other antimicrobials in E. coli 288 (23.3%) and Enterococcus spp. 163 (23.2%), suggesting retained efficacy for some UTIs. Conclusion: The study highlights evolving antimicrobial resistance patterns in uropathogens over five years, with increasing resistance to commonly prescribed empirical antibiotics, particularly cephalosporins and fluoroquinolones. Despite this, nitrofurantoin, linezolid, vancomycin, and selected reserve drugs maintained better susceptibility profiles against several isolates. Routine surveillance, evidencebased empirical therapy, institution-specific antibiograms and antimicrobial stewardship are essential to optimise clinical outcomes and curb the emergence of antimicrobial resistance.