COMPREHENSIVE GENOMIC CHARACTERIZATION OF BOVINE AND HUMAN SHIGA TOXIN-PRODUCING ESCHERICHIA COLI IN ISRAEL

Assaf Rokney 1 Moti Baum 1 Einav Anuka 1 Lea Valinsky 1 Jacob Moran-Gilad 2,3 Shlomo Blum 4
1Government Central Laboratories, Public Health Services, Ministry of Health, Jerusalem, Israel
2Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
3Public Health Services, Ministry of Health, Jerusalem, Israel
4Division of Bacteriology, Kimron Veterinary Institute, Beit Dagan, Israel

Shiga toxin-producing E. coli (STEC) is a foodborne pathogen of major public health importance. Cattle is the main animal reservoir of STEC and an important source of environmental and food contamination worldwide. This study is the first to perform a whole genome sequencing analysis of STEC isolates in Israel, with focus on phylogeny and zoonotic potential, virulence profiles and antimicrobial resistance.

We studied human clinical isolates (hSTEC, 2009-2017, n=47) and veterinary isolates from dairy and beef cattle stools (bSTEC, 2013-2014, n=91). Among hSTEC, 4 serotypes and 5 Multilocus Sequence Types (STs) were recognized, predominantly O157:H7, ST-11 (83%), and 98% were typical Enterohemorhagic E. coli (EHEC). Shiga toxin (stx) subtypes among hSTEC were limited to stx1a, stx1c, stx2a, stx2c. The 91 bSTEC accounted for 23 serotypes, 21 STs and 11 stx subtype combinations. The various and distinct serogenotypes of bSTEC were mostly clonal. E. coli O157:H7 and EHEC were not prevalent among bSTEC and accounted for 8% and 22% of the strains, respectively.

The only serotype common to human and bovine isolates was O157:H7. wgMLST analysis revealed clustering of bovine, human and food isolates of EHEC O157:H7, indicative of zoonotic transmission. bSTEC included other potentially pathogenic EHEC not currently observed among clinical cases (O98:H21, O150:H2, O49:H10, O5:H9 and O172:H25). STEC strains contained a variety of virulence factors as well as resistance genes predictive of phenotypic resistance (ß-lactams, phenicols, aminoglycosides, tetracyclines, macrolides and sulfonamides). ESBL genes were not detected. The resistance genes bla-TEM-1, strA, sul, tetA were significantly more prevalent in eae-positive strains.

This first genomic study of the STEC population in Israel indicates EHEC and in particular E. coli O157:H7 are significant zoonotic pathogens linked to cattle. Further surveillance using whole genome sequence analysis should be implemented in order to support case investigation and veterinary and food control.









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