title: Diversity of CRISPR loci and virulence genes in pathogenic Escherichia coli isolates from various sources.
abstract: Shiga toxin-producing Escherichia coli (STEC) strains, including those of O157:H7 and the "big six" serogroups (i.e., O26, O45, O103, O111, O121, and O145) are food-borne pathogens that pose a serious health threat to humans. Ruminants, especially cattle, are a major reservoir for O157 and non-O157 STEC. In the present study, 115 E. coli strains isolated from small and very small beef processing plants were screened for virulence genes (stx1, stx2, eae) using a multiplex polymerase chain reaction (PCR). Thirteen (11.3%) of the 115 isolates tested positive for stx1, stx2, or eae genes, but only 4 (3.5%) tested positive for either stx1 or stx2. A multiplex PCR reaction targeting eight O-serogroups (O26, O45, O103, O111, O113, O121, O145, O157) identified 12 isolates as O26, O103, O111, or O145, with E. coli O26 being the most predominant serogroup (61.5%). The thirteen isolates were further analyzed using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) subtyping. Consistent with previous studies, CRISPR alleles from strains of the same serogroup were similar in their spacer content and order, regardless of the isolation source. A completely different CRISPR allele was observed in one isolate ("7-J") which exhibited a different O-serogroup (O78). Our results confirmed previous findings that CRISPR loci are conserved among phylogenetically-related strains. In addition, 8 E. coli O26 isolates and a collection of 42 E. coli O26 isolates were screened for 12 enterohemorrhagic E. coli-specific genes. Seven genes (ECs848-Hypothetical Protein, ECs2226-Hypothetical Protein, ECs3857-nleB, ECs3858-Hypothetical Protein, ECs4552-escF, ECs4553-Hypothetical Protein, and ECs4557-sepL) were found in all 50 isolates. An additional 5 genes (ECs1322-ureA urease subunit γ, ECs1323-ureB urease subunit β, ECs1326-ureF, ECs1561-Hypothetical Protein, and ECs1568-Hypothetical Protein) were found to be highly prevalent in isolates from human sources, while lower in isolates from beef processing plants, cattle, and other sources. This finding indicates the possible role of these genes in virulence of human O26 strains.
authors.affiliation: Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA; Department of Food Science, Ginling College, Nanjing Normal University, Nanjing 210097, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Yin
authors.affiliation: Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Dudley
authors.affiliation: Department of Food Science, The Pennsylvania State University, 202 Rodney A. Erickson Food Science Building, University Park, PA 16802, USA. Electronic address: cnc3@psu.edu.
authors.forename: Catherine N
authors.initials: CN
authors.lastname: Cutter
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics*; D000818:Animals; D015373:Bacterial Typing Techniques; D002417:Cattle / Q000382:microbiology; D002418:Cattle Diseases; D064112:Clustered Regularly Interspaced Short Palindromic Repeats / Q000235:genetics; D004927:Escherichia coli Infections / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D008460:Meat; D008462:Meat-Packing Industry; D060885:Multiplex Polymerase Chain Reaction; D022622:Shiga Toxin 1 / Q000235:genetics*; D022641:Shiga Toxin 2 / Q000235:genetics*; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity
chemical_list: D018829:Adhesins, Bacterial; D029968:Escherichia coli Proteins; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; C073819:eaeA protein, E coli
keywords: CRISPR PCR; Diversity; Shiga toxin-producing Escherichia coli; Virulence genes