Analysis of Etiology of Community-Acquired and Nosocomial Urinary Tract Infections and Antibiotic Resistance of Isolated Strains: Results of a 3-Year Surveillance (2020–2022) at the Pediatric Teaching Hospital in Warsaw

Urinary tract infections (UTIs) remain the most common infections diagnosed in outpatients and hospitalized patients. This study was designed to determine the patterns of antibiotic resistance and the prevalence of uropathogens causing UTIs in pediatric patients hospitalized between 1 January 2020 and 31 December 2022 at Teaching Hospital in Warsaw. The most frequent species isolated from urine samples were E. coli (64.5%), Klebsiella spp. (11.6%), and Enterococcus spp. (6.1%). UTIs caused by Enterobacter spp., Enterococcus spp., and Klebsiella spp. were significantly more common in children younger than three months of age than in children older than three months (p < 0.001). Trimethoprim and trimethoprim–sulfamethoxazole were the least active compounds against Enterobacterales with the resistance of E. coli, Klebsiella spp., P. mirabilis, and Enterobacter spp. in the range of 26.7/25.2%, 48.4/40.4%, 51.1/40.4%, and 15.8/13.2% respectively. Ampicillin was also found to have resistance rates for E. coli of 54.9% and P. mirabilis of 44.7%. Cefalexin and cefuroxime were highly active towards Enterobacterales except for Klebsiella spp., in which the resistance level reached 40%. Regarding third- and fourth- generation cephalosporins, resistance in E. coli and P. mirabilis was observed in approximately 2–10% of the isolates, but in Klebsiella spp. and Enterobacter spp. ranged over 30%. The resistance of Enterobacterales to carbapenems, nitrofurantoin, and fosfomycin was below 1%. The quinolones resistance was very high for Klebsiella spp. (31.1%) and P. mirabilis (29.8%) and three times lower for E. coli (11.9%), P. aeruginosa (9.3%), Enterobacter spp. (2.6%), and E. faecalis (4.6%). Resistance to multiple antibiotic classes was identified in 396 Enterobacterales strains, 394 of which were multi-drug resistant (MDR) and 2 were extensive drug-resistant (XDR). In the case of E. coli, 30% of isolates were MDR, with the proportion of strains having this exact resistance pattern similar in all of the analyzed years; no E. coli XDR strains were isolated. The number of Klebsiella spp. MDR strains was much higher in 2022 (60%) than in 2021 (47.5%). In the analyzed time, only one strain of K. pneumonia XDR, producing New Delhi metallo-β-lactamase, was isolated. Monitoring infection trends is essential to improve control and limit the rise of bacterial resistance.