High Prevalence of Multidrug-Resistant Uropathogenic Escherichia coli with Marked Gender-Associated Resistance Patterns: A Retrospective Study from Northern Iran

Background Urinary tract infections (UTIs) are among the most common bacterial infections worldwide, with Escherichia coli (E. coli) accounting for up to 90% of cases. Risk factors include anatomical differences, poor hygiene, pregnancy, urinary obstruction, catheter use, urethral reflux, and spermicidal contraceptives. Common empiric treatments include amoxicillin, ciprofloxacin, amoxicillin/clavulanic acid, nitrofurantoin, and trimethoprim, but increasing antimicrobial resistance (AMR) complicates therapy. This study aimed to evaluate in vitro resistance patterns of common antimicrobials against uropathogenic E. coli (UPEC) and assess trends over time to inform empiric treatment strategies and reduce failures. Methods This retrospective, record-based study analyzed culture and sensitivity (C/S) reports of urine samples from inpatients at Imam Khomeini, Boo-Ali Sina, Razi, Zare, and Fatemeh Zahra hospitals in Sari, Iran, from March 2021 to the end of 2022. Ethical approval and laboratory permission were obtained. E. coli was identified using standard microbiological and biochemical methods. Antimicrobial susceptibility testing used the Kirby-Bauer disk diffusion method on Mueller-Hinton agar per CLSI 2021 guidelines, testing penicillins, cephalosporins, quinolones, aminoglycosides, sulfonamides, carbapenems, and nitrofurantoin. Data were compiled year-wise, with statistical analysis via IBM SPSS version 20. Results Of 1,804 E. coli -positive isolates, 64.7% were from females and 35.3% from males; age was recorded for 1,627 patients, with 41–60 years most frequent (33.3%). Highest susceptibility was to amikacin (92.0%), nitrofurantoin (83.7%), and gentamicin (80.3%); highest resistance to ampicillin (93.4%), ceftriaxone (66.1%), ciprofloxacin (63.9%), cefotaxime (63.8%), and cotrimoxazole (62.4%). Resistance was significantly higher in females for most agents, including ciprofloxacin (78.0% vs. 36.8%) and nitrofurantoin (84.4% vs. 3.0%, p = 0.027). Over 70% of isolates were MDR. Intermediate susceptibility was low (0.0-3.2%). Highest resistance rates occurred in patients with 7–10 day hospital stays. Conclusion High AMR in UPEC, particularly to empiric agents, underscores therapeutic challenges. Gender differences suggest tailored approaches for females. Regular surveillance is essential to optimize empiric therapy, minimize failures, and curb MDR spread in this region.