SUNGKYUNKWAN UNIVERSITY SCHOOL OF MEDICINE
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Research Highlights
Comparison of hybrid- and mono-pathotype Escherichia coli isolates from South Korea based on whole genome analysis and cytotoxicity assay
Jong Hyun Shin, Min Seok Kim, Ji Young Choi, Sunju Kim, Kun Taek Park, Mi-Ran Seo, Seung-Hyun Jung, Yeun-Jun Chung, Hyeri Seok, Hae Suk Cheong, Ki-Tae Kwon, Bo Kyeung Jung, Cheol-In Kang, Doo-Ryeon Chung, Dongwoo Shin, Kwan Soo Ko*
This study investigated hybrid-pathotype Escherichia coli strains carrying virulence genes from multiple classical pathotypes, using whole-genome sequencing of 292 isolates collected from humans, livestock, and environmental sources in South Korea.
Of 193 intestinal pathogenic isolates, 63 (32.6%) were hybrid pathotypes, predominantly STEC/EPEC (n=38) and STEC/ETEC (n=23). STEC/EPEC isolates came exclusively from humans (mostly O157:H7), while STEC/ETEC were found only in pigs. Phylogenetic and LEE pathogenicity island synteny analyses revealed that STEC/EPEC hybrids likely originated from an EPEC genomic backbone that acquired stx genes via bacteriophage, whereas STEC/ETEC hybrids appeared to derive from a STEC backbone, indicating that hybrid emergence occurs through multiple independent mechanisms.
The two hybrid types exhibited opposite cytotoxicity profiles in LDH assays: STEC/ETEC showed significantly higher cytotoxicity than either constituent mono-pathotype, while STEC/EPEC showed lower cytotoxicity, suggesting that the genomic background determines pathogenic outcome. SPLASH analysis further identified five gene modules linked to elevated cytotoxicity in STEC/ETEC: flagella motility, iron uptake, adhesion pili, plasmid conjugation, and T3SS. These findings highlight the dynamic nature of pathogenic E. coli evolution and emphasize the need for hybrid-aware, One Health surveillance.
Of 193 intestinal pathogenic isolates, 63 (32.6%) were hybrid pathotypes, predominantly STEC/EPEC (n=38) and STEC/ETEC (n=23). STEC/EPEC isolates came exclusively from humans (mostly O157:H7), while STEC/ETEC were found only in pigs. Phylogenetic and LEE pathogenicity island synteny analyses revealed that STEC/EPEC hybrids likely originated from an EPEC genomic backbone that acquired stx genes via bacteriophage, whereas STEC/ETEC hybrids appeared to derive from a STEC backbone, indicating that hybrid emergence occurs through multiple independent mechanisms.
The two hybrid types exhibited opposite cytotoxicity profiles in LDH assays: STEC/ETEC showed significantly higher cytotoxicity than either constituent mono-pathotype, while STEC/EPEC showed lower cytotoxicity, suggesting that the genomic background determines pathogenic outcome. SPLASH analysis further identified five gene modules linked to elevated cytotoxicity in STEC/ETEC: flagella motility, iron uptake, adhesion pili, plasmid conjugation, and T3SS. These findings highlight the dynamic nature of pathogenic E. coli evolution and emphasize the need for hybrid-aware, One Health surveillance.