Emergence of sequence type 131 clone carrying genes in Guilan Province, Northern Iran.

Unlabelled: Extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales complicate clinical management, as they are resistant to standard antibiotics and often necessitate intricate treatment plans. As a result, continuous monitoring is essential to prevent the spread of resistant strains and ensure effective treatment options are available. Enterobacterales are humans' primary contributors to urinary tract infections (UTIs). Among these, () sequence type 131 (ST131), which carries β-lactamase genes with significant virulence potential, has been documented globally. ST131 mostly belongs to the serotypes O25 and O16 and is a well-defined subclone of the FimH30 and FimH30-Rx. We aimed to evaluate the impact of the ST131 clone carrying three β-lactamase genes-the , , and genes-in the antibiotic resistance pattern of ESBL-producing (ESBL-EC) from UTIs in Guilan, Iran. The phenotypic confirmatory disc diffusion test (PCDDT), according to CLSI recommendations, was utilized to detect ESBL production. The ESBL-EC isolates were screened for the ST131 clone using specific PCR of O25b, O16, H30, and H30-Rx. Out of the 107 ESBL-EC, 70 (65.4%) showed as ST131. Among the ST131 clones, the highest frequency belonged to the ST131-H30 (98.6%). Among the beta-lactam antibiotics, both the ST131 and non-ST131 groups exhibited complete resistance (100%) to cefotaxime, ampicillin, amoxicillin-clavulanate, cephalothin, cefixime, and ceftriaxone while demonstrating the greatest susceptibility to imipenem ( = 0%). In the case of non-beta-lactam antibiotics, both groups showed significant resistance (approximately 91%) to nalidixic acid, while displaying the highest susceptibility to nitrofurantoin (up to 83%). Our study confirmed the dominance of the ST131 clone among the ESBL-EC and β-lactamase genes associated with the transmission of this pandemic clone.

Importance: Various antibiotic resistance and virulence genes highlight challenges in clinical management and emphasize the need for effective treatment strategies to reduce the risks associated with UTIs. Continuous research is essential to improve knowledge and create innovative approaches to tackle these urological conditions. Our study confirmed the predominance of genes related to the ST131 clone, including O25, O16, H30, and H30-Rx, among ESBL-EC. We found that the ST131 clone carried , , and and was expanded in our locale. The clones differed significantly in resistance, susceptibility, and relative susceptibility, only in antibiotic resistance in the case of nitrofurantoin ( < 0.001). Combining resistance genes in the ST131 clone can facilitate its rapid and successful global spread.