Comprehensive analysis of antibiotic resistance in Enterobacteriaceae from outpatient urine cultures: Implications for empirical therapy.

Objective: Urinary tract infections (UTIs) are among the most common bacterial infections. The misuse of antibiotics is one of the factors contributing to the global increase in antimicrobial resistance (AMR), making the management of UTIs more challenging. Our study aims to evaluate the causative agents of UTIs and the factors influencing resistance, as well as to identify antibiotics that can be used in the outpatient treatment of patients diagnosed with UTIs.

Methods: This retrospective study was conducted by collecting urine sample results between 2015-2023. The culture results of the urine samples and the results of the antibiotic sensitivity tests of the Enterobacteriaceae isolates were analyzed. Antimicrobial susceptibilities of the isolates were defined using the VITEK^®2 Compact system (bioMérieux, Marcyl'Etoile, France) and PheonixTM (Becton-Dickinson, NJ, USA). All sensitivity statuses were determined according to EUCAST standards. Data analysis was conducted using SPSS software version 23.

Results: 1842 culture results were included. 71.5% of the included samples were from women, and the average age of the cases was 63±18. The most commonly grown agent in urine cultures is Escherichia coli. The resistance profile of the Enterobacteriaceae to antibacterial agents was examined, and it was found that the highest resistance rates were against ampicillin (77.92%), cefazolin (52.36%), ciprofloxacin (49.5%), and trimethoprim/sulfamethoxazole (45.5%), while the lowest resistance rates were against meropenem (4.9%), amikacin (7.6%), fosfomycin (11.4%), and nitrofurantoin (11.6%). Comparing resistance rates before and after 2019, a significant increase in resistance to amikacin and nitrofurantoin was observed (p≤0.001). It was found that resistance rates were higher in urine samples from male cases.

Conclusion: Our study revealed that patients should be carefully evaluated in terms of the necessity of culture requests and patients should be informed about culture requests due to the high rate of non-growth and contamination in urine culture results. The high rates of antimicrobial resistance were detected, and the outpatient treatment options of UTI patients are narrowing which can increase hospital admission rates. Our study is important because it shows that nitrofurantoin and fosfomycin can be included in the outpatient and empirical treatment of UTI patients.