Investigations of Escherichia coli ST131 and H30Rx subclone from clinical samples

Escherichia coli is a highly adaptable Gram-negative bacterium, commonly part of the gut microbiota in humans and animals, yet capable of causing severe extraintestinal infections. Among its lineages, Sequence Type 131 (ST131) has emerged as a globally disseminated, multidrug-resistant, high-risk clone with remarkable capacity for systemic infections. This study provides a comprehensive molecular epidemiological characterization of 160 clinical E. coli isolates, collected between 15.09.2021 and 28.02.2022, assessing antimicrobial resistance profiles, virulence gene carriage, phylogenetic group distribution, prevalence of ST131 and H30Rx subclone, and biofilm-forming capacity. Isolates were identified by conventional and automated methods, with molecular analyses performed via in-house PCR assays. Our results reveal a striking 69.38% prevalence of ST131, with 95.5% harboring virulence genes and 81.99% exhibiting biofilm formation. Notably, ST131-positive isolates demonstrated extensive resistance to multiple antimicrobial classes, including ESBL production, and were dominated by the H30Rx subclone. Specifically, 73.87% of ST131 isolates were ESBL-positive, fluoroquinolone resistance was observed in 81.37%, while aminoglycoside resistance rate remained very low. The H30Rx subclone was strongly associated with ESBL positivity and multidrug resistance. Moreover, integron carriage diversity and strong association with fimA virulence gene further highlight the adaptive versatility of this clone. Given that ST131 and its H30Rx subclone are recognized as global pandemic lineages associated with multidrug resistance and severe infections, their detection in our cohort emphasizes both the clinical relevance and the public health risk posed by these clones. Our findings underscore the urgent need for targeted surveillance and control strategies, offering novel epidemiological insights into the molecular diversity and clinical threat posed by E. coli ST131 in Turkey.