Microbial Epidemiology and Antimicrobial Resistance Trends in Urinary Isolates from a Tertiary Hospital in Rome, Italy: A Retrospective Study (2022–2025)

Background and Objectives: Urinary tract infections are common in clinical practice, but in hospital settings, especially among older and catheterized patients, the microbial ecology and resistance burden may differ substantially from community-acquired infections. Local surveillance is therefore essential to support appropriate empirical treatment and antimicrobial stewardship. The objective is to describe the microbiological epidemiology of urinary isolates in a tertiary hospital and evaluate temporal trends in antimicrobial resistance among the most frequently isolated microorganisms. Materials and Methods: This retrospective observational study analyzed microbiology laboratory data from Tor Vergata University Hospital, Rome, Italy, collected from January 2022 to June 2025. After WHONET-based deduplication using a 30-day repeat-isolate rule, 5788 deduplicated urinary isolates and 85,888 microorganism–drug associations were included. Descriptive analyses, cumulative antibiograms/antimycograms, and quarterly resistance trends were assessed using univariable and multivariable regression analyses. Results: The population was predominantly elderly, inpatient, and catheter-exposed. Gram-negative organisms predominated, followed by Gram-positive bacteria and fungi. The most frequent isolates were E. coli, K. pneumoniae, E. faecalis, and C. albicans. Although microorganism distribution remained broadly stable over time, resistance increased in several clinically relevant organism–drug combinations, especially among major Enterobacterales. Conclusions: In this high-complexity hospital population, urinary isolates showed a relatively stable microorganism distribution but progressive changes in susceptibility among selected urinary isolates. These findings support setting-specific microbiological surveillance and stewardship-informed empirical treatment strategies.