title: Isolation and characterization of shiga toxin-producing escherichia coli serogroups O26, O45, O103, O111, O113, O121, O145, and O157 shed from range and feedlot cattle from postweaning to slaughter.
abstract: Cattle are the main reservoirs for Shiga toxin-producing Escherichia coli (STEC) strains. E. coli O26, O45, O103, O111, O121, O145, and O157 are among the STEC serogroups that cause severe foodborne illness and have been declared as adulterants by the U.S. Department of Agriculture, Food Safety and Inspection Service. The objectives of this study were (i) to estimate the prevalence of non-O157 STEC and E. coli O157 in naturally infected beef cows and in steer calves at postweaning, during finishing, and at slaughter and (ii) to test non-O157 STEC isolates for the presence of virulence genes stx1, stx2, eaeA, and ehlyA. Samples were collected from study animals during multiple sampling periods and included fecal grabs, rectal swabs, and midline sponge samples. Laboratory culture, PCR, and multiplex PCR were performed to recover and identify E. coli and the virulence genes. The prevalence of non-O157 STEC (serogroups O26, O45, O103, O111, O121, O113, and O145) fecal shedding ranged from 8% (4 of 48 samples) to 39% (15 of 38 samples) in cows and 2% (1 of 47 samples) to 38% (9 of 24 samples) in steer calves. The prevalence of E. coli O157 fecal shedding ranged from 0% (0 of 38 samples) to 52% (25 of 48 samples) in cows and 2% (1 of 47 samples) to 31% (15 of 48 samples) in steer calves. In steer calves, the prevalence of non-O157 STEC and E. coli O157 was highest at postweaning, at 16% (15 of 96 samples) and 23% (22 of 96 samples), respectively. Among the 208 non-O157 STEC isolates, 79% (164 isolates) had stx1, 79% (165 isolates) had stx2, and 58% (121 isolates) had both stx1 and stx2 genes. The percentage of non-O157 STEC isolates encoding the eaeA gene was low; of the 165 isolates tested, 8 (5%) were positive for eaeA and 135 (82%) were positive for ehlyA. Findings from this study provide further evidence of non-O157 STEC shedding in beef cows and steer calves particularly at the stage of postweaning and before entry into the feedlot.
authors.affiliation: College of Public Health and Health Professions, University of Florida, Gainesville, Florida 32610-0136, USA; Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
authors.forename: Abel B
authors.initials: AB
authors.lastname: Ekiri
authors.affiliation: Dickinson Research Extension Center, North Dakota State University, 1041 State Avenue, Dickinson, North Dakota 58601, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Landblom
authors.affiliation: Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
authors.forename: Dawn
authors.initials: D
authors.lastname: Doetkott
authors.affiliation: Department of Statistics, North Dakota State University, Fargo, North Dakota 58108-6050, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Olet
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Biosciences Research Laboratory, Fargo, North Dakota 58102-2765, USA.
authors.forename: Weilin L
authors.initials: WL
authors.lastname: Shelver
authors.affiliation: Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, North Dakota 58108-6050, USA; Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762, USA. mkhaitsa@cvm.msstate.edu.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Khaitsa
mesh_terms: D000003:Abattoirs; D000818:Animals; D002417:Cattle / Q000254:growth & development / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D005260:Female; D005506:Food Contamination / Q000032:analysis; D008297:Male; D008460:Meat / Q000382:microbiology; D022621:Shiga Toxin / Q000235:genetics / Q000378:metabolism*; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D014481:United States; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D037521:Virulence Factors; D022621:Shiga Toxin