Molecular characterization of enterohemorrhagic Escherichia coli hemolysin gene (EHEC-hlyA)-harboring isolates from cattle reveals a diverse origin and hybrid diarrheagenic strains |
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| Institution: | 1. Department of Pathobiology, Faculty of Veterinary Medicine, Garmsar Branch, Islamic Azad University, Garmsar, Iran;2. European Union Reference Laboratory for Escherichia coli, Istituto Superiore di Sanita, Dipartimento di Sanita Pubblica Veterinaria e Sicurezza Alimentare, Rome, Italy;1. Department of Food Hygiene and Food Technology, Veterinary Faculty, University of León, Spain;1. Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary;2. Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia;3. University of Veterinary Medicine Vienna, Institute for Milk Hygiene, Milk Technology and Food Science, Vienna, Austria;4. AGES, Institute for Medical Microbiology and Hygiene, Graz, Austria;5. Federal Institute for Risk Assessment, Berlin, Germany;6. National Laboratory of Health, Environment and Food, Center for Microbiologic Analysis of Food, Water and other Environmental Samples Maribor, Slovenia;7. ID Genomics, Seattle, WA, USA;8. National Center for Epidemiology, Budapest, Hungary;1. Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan;2. Faculty of Veterinary Medicine, Sadat City University, Sadat City, Egypt;3. Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan |
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| Abstract: | In the present study we investigated the occurrence of Escherichia coli strains harboring the gene encoding enterohemorrhagic E. coli hemolysin (EHEC-HlyA) in cattle and the association of this gene with various diarrheagenic E. coli (DEC) pathotypes. First, the bovine E. coli isolates were screened for EHEC-hlyA gene by PCR, and then they were characterized for the phylogenetic groups and the presence of the major virulence genes of different DEC pathotypes. In total, 25 virulence gene profiles were observed in 54 EHEC-hlyA+ isolates that reflect a considerable heterogeneity. The EHEC-hlyA+ strains were mostly associated with EHEC (72%), while only 7.4% were enteropathogenic E. coli (EPEC). We also showed the presence of estA gene of enterotoxigenic E. coli (ETEC) in 6 isolates (11.1%). Interestingly, two of the estA+ strains showed hybrid pathotypes with one carrying eae/estA (EPEC/ETEC), and the other one stx2/astA/estA (EHEC/ETEC). None of the isolates were related to enteroaggregative E. coli (EAggEC), enteroinvasive E. coli (EIEC), and necrotoxigenic E. coli (NTEC). The EHEC-plasmid encoded genes occurred in seven different combinations with EHEC-hlyA/saa/subA/espP being the most prevalent (46.3%). All stx −/eae+ strains carried O island 57 (OI-57) molecular marker(s) that may indicate these to be the progenitors of EHEC or strains losing stx. The most prevalent phylogroup was B1 (61.1%), but the most heterogeneous strains including the hybrid strains belonged to A phylogroup. Overall, our results indicate that cattle EHEC-hlyA encoding E. coli isolates consist of diverse diarrheagenic strains with the possible existence of hybrid pathotypes. Future studies are required to clarify the evolutionary aspects and clinical significance of these strains in humans and domestic animals. |
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