Etiological spectrum and antimicrobial resistance of the most frequently isolated pathogens, associated with urinary tract infections in ambulatory patients

Introduction: Urinary tract infections (UTIs) are among the most common infections both in the community and in the hospital setting. Aim: The aim of this study is to investigate the etiological spectrum and antimicrobial resistance of most frequently isolated pathogens, associated with UTIs in ambulatory patients in Varna city, Bulgaria during a seven-month period (October 2020–April 2021). Materials and Methods: A total of 1600 urine samples, collected from patients with suspected UTIs were tested. Screening for bacterial growth was done by HM&L Uroquattro instrument (ALIFAX, Italy). Species identification and antimicrobial susceptibility testing were performed by VITEK 2 Compact System (bioMerieux) and Kirby-Bauer disk diffusion method. Results: E. coli was the most commonly isolated uropathogen regardless of the age group (48%, n = 61), followed by Enterococcus faecalis (33%, n = 42) and other representatives of order Enterobacterales (13.3%, n = 18). The resistance rates in the group of Gram-negative isolates (n = 79) in decreasing order were as follows: ampicillin, 64.5% > trimethoprim/sulfamethoxazole, 36% > ciprofloxacin, 29.1% > amoxicillin-clavulanic acid, 27.8% > cefuroxime, levofloxacin, 21.5% > fosfomycin, 13.1% > ceftriaxone, 12.6% > ceftazidime, 10.1% > gentamicin, nitrofurantoin, 6.5% > nitroxoline, 4.9%. The resistance rates among the isolates of E. faecalis (n = 42) were as follows: ciprofloxacin, 28.6% > gentamicin, 23.8% > levofloxacin, 19% > nitrofurantoin, 4.7% > amoxicillin, 2.4%. No resistance to meropenem, amikacin, vancomycin, and teicoplanin was found in the studied collection of isolates (n = 127). Conclusion: The etiological spectrum of UTIs in ambulatory patients was dominated by E. coli , followed by E. faecalis. In the group of Gram-negative uropathogens, high resistance rates to ampicillin, trimethoprim/sulfamethoxazole and quinolones were detected. Third-generation cephalosporins, fosfomycin, nitrofurantoin and nitroxoline retained very good activity. Among Enterococcus faecalis isolates, the second most commonly isolated bacterial species, a decreased activity of quinolones was found too, but the aminopenicillins and nitrofurantoin remain highly active.