Frequency of Extended-spectrum Beta-Lactamases-Producing Escherichia coli Among Out- and In-patients in Rafsanjan City, Iran

Background: The frequency of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli strains among clinical isolates has been steadily increasing, leading to limited treatment options. Objectives: This study aimed to assess the antibiotic sensitivity of E. coli and the frequency of ESBL isolates among both out-patients and in-patients. Methods: A total of 390 E. coli isolates were received at the Ali-Ebn-e-Abitaleb Hospital laboratory in Rafsanjan. The antibiogram, as well as the phenotypic and genotypic detection of ESBL isolates, were conducted using Kirby-Bauer, combination disk confirmatory, and polymerase chain reaction tests, respectively. Results: Of all the E. coli isolates, 45.6% exhibited ESBL production. Among these isolates, 46.1% were obtained from hospital wards, while 42.5% were from outpatients. Meropenem and imipenem displayed sensitivities of 97.2% and 93.3%, respectively, whereas amikacin and nitrofurantoin showed sensitivities of 89.7% and 85.6%, respectively, for all isolates. Notably, ceftriaxone, cefotaxime, cefixime, ampicillin, co-trimoxazole, and nalidixic acid demonstrated high resistance rates, surpassing 50%. ESBL-producing isolates were more frequently observed in blood samples (65%) and wounds (60%) compared to other tested isolates. Approximately 8.6% of isolates carried a single type of ESBL gene, while 38.5% carried multiple ESBL genes. Conclusions: The data indicate a prevalence of ESBL-producing E. coli isolates among both out-patients and in-patients, with some of them acquiring two or three types of ESBL enzymes. As a result, their ability to hydrolyze antibiotics has increased, leading to their higher occurrence in clinical samples.