In Silico Analysis of Shiga Toxin-Producing Escherichia coli O157:H7 Strains from Presumptive Super- and Low-Shedder Cattle

Author:

Bumunang Emmanuel W.1,Castro Vinicius S.23,Alexander Trevor1,Zaheer Rahat1ORCID,McAllister Tim A.1ORCID,Guan Le Luo4,Stanford Kim3ORCID

Affiliation:

1. Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, AB T1J 4B1, Canada

2. Faculty of Agronomy and Zootechnics, Federal University of Mato Grosso (UFMT), Cuiabá 78010-715, Brazil

3. Department of Biological Sciences, University of Lethbridge, Lethbridge, AB T1K 1M4, Canada

4. Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P9, Canada

Abstract

Cattle are the primary reservoir for STEC O157, with some shedding >104 CFU/g in feces, a phenomenon known as super-shedding (SS). The mechanism(s) responsible for SS are not understood but have been attributed to the environment, host, and pathogen. This study aimed to compare genetic characteristics of STEC O157 strains from cattle in the same commercial feedlot pens with SS or low-shedding (LS) status. Strains from SS (n = 35) and LS (n = 28) collected from 11 pens in three feedlots were analyzed for virulence genes, Shiga toxin-carrying bacteriophage insertion sites, and phylogenetic relationships. In silico analysis showed limited variation regarding virulence gene profiles. Stx-encoding prophage insertion sites mrlA and wrbA for stx1a and stx2a, respectively, were all occupied, but two isolates had fragments of the stx-carrying phage in mrlA and wrbA loci without stx1a and stx2a. All strains screened for lineage-specific polymorphism assay (LSPA-6) were 111111, lineage I. Of the isolates, 61 and 2 were clades 1 and 8, respectively. Phylogenetic analysis revealed that pens with more than one SS had multiple distantly related clusters of SS and LS isolates. Although virulence genes and lineage were largely similar within and across feedlots, multiple genetic origins of strains within a single feedlot pen illustrate challenges for on-farm control of STEC.

Funder

Results-Driven Agricultural Research

Beef Cattle Research Council

Publisher

MDPI AG

Subject

Health, Toxicology and Mutagenesis,Toxicology

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