Phylogenetic analysis and characterization of hybrid enteroaggregative/uropathogenic Escherichia coli strains isolated from urinary tract infection.

BACKGROUND

Hybrid EAEC/UPEC Escherichia coli strains are emerging uropathogens that combine intestinal and extraintestinal virulence traits through horizontal gene transfer. Although relatively uncommon, these hybrids exhibit strong biofilm formation, enhanced epithelial adherence, and notable antimicrobial resistance, underscoring the need for detailed molecular characterization and epidemiological assessment. The present study aimed to determine the frequency of hybrid EAEC/UPEC isolates among E. coli recovered from patients with urinary tract infections and to characterize their lineage using PCR-based sequence type screening, phylogenetic grouping, and antibiotic resistance profiling.

METHODS

This study analyzed 199 archived E. coli isolates from UTI patients, assessing antimicrobial resistance, ESBL production, and virulence genes. PCR was used to characterize their lineage using PCR-based sequence type screening and phylogenetic grouping.

RESULTS

Analysis of 199 isolates identified 17 EAEC/UPEC hybrids (8.5%), predominantly from female patients and children. All hybrids carried aatA, fyuA, and fimH, with variable presence of aap, aggR, and chuA. High resistance rates were observed, with 94.1% classified as MDR and 47.1% as ESBL producers. blaCTX-M, blaTEM, and qnrS were the main resistance genes detected. Serogrouping identified O25 as the predominant serogroup. Serogrouping showed O25 as the predominant serotype, while phylogroup B2 and sequence type ST131 were most common among hybrids.

CONCLUSIONS

This study identified 8.5% of urinary E. coli isolates as hybrid EAEC/UPEC strains. High multidrug resistance, particularly to trimethoprim-sulfamethoxazole, nalidixic acid, and cefotaxime, underscores major therapeutic challenges. These findings highlight the clinical importance of emerging hybrid pathotypes and the need for strengthened molecular surveillance.