title: Escherichia coli O157:H7 and non-O157 Shiga toxin-producing E. coli in healthy cattle, sheep and swine herds in Northern Spain.
abstract: Three-hundred and forty-five herds (17 swine, 122 dairy sheep, 124 beef and 82 dairy cattle) were investigated for prevalence of Shiga toxin-producing Escherichia coli (STEC). Rectal faecal samples were selectively enriched and then examined by immunodetection techniques (Immunomagnetic Separation with anti-E. coli O157 Dynabeads, ImmunoMagnetic cell Separation (IMS) and automated enzyme-linked fluorescent immunoassay using VIDAS) and polymerase chain reaction (PCR) (rfbE and fliC genes) to assess the prevalence of E. coli O157:H7. Prevalence of non-O157 STEC was estimated by PCR screening for stx genes of 10 lactose-positive colonies grown on MacConkey agar after enrichment. PCR was used on all STEC isolates to detect stx(1), stx(2), eaeA and E-hlyA genes. Both immunodetection methods showed a moderate-good level of agreement (kappa = 0.649) but IMS showed 87.5% complementary sensitivity. Prevalence of positive herds for E. coli O157:H7 was estimated at 8.7% for sheep and 3.8% for cattle, whereas all the porcine herds tested negative. Non-O157 STEC were also absent from swine, but were isolated more frequently from ovine (50.8%) than bovine herds (35.9%). Within-herd prevalences of excretion of E. coli O157:H7 established by individual testing of 279 sheep (six herds) and 30 beef cattle (one herd) were 7.3% and 6.7% respectively. PCR analysis of 49 E. coli O157:H7 and 209 non-O157 isolates showed a different distribution of virulence genes. All E. coli O157:H7 were stx(2) gene-positive, eaeA was detected in 95.9%, and the toxigenic profile stx(2)/eaeA/E-hlyA was present in 75.5% of the isolates. Among the non-O157 STEC, prevalence of eaeA was significantly lower (5.3%) and E-hlyA was present in 50.2% of the isolates but only sporadically associated with eaeA. stx(2) was predominant in non-O157 isolates from cattle, whereas in sheep the combination stx(1)/stx(2) was more prevalent. This study demonstrated the wide distribution of STEC in ruminant herds, which represent an important reservoir for strains that pose a potential risk for human infections.
authors.affiliation: Department of Animal Health and Production, NEIKER - Instituto Vasco de Investigación y Desarrollo Agrario, Berreaga 1, 48160 Derio, Bizkaia, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Oporto
authors.forename: J I
authors.initials: JI
authors.lastname: Esteban
authors.forename: G
authors.initials: G
authors.lastname: Aduriz
authors.forename: R A
authors.initials: RA
authors.lastname: Juste
authors.forename: A
authors.initials: A
authors.lastname: Hurtado
mesh_terms: D000818:Animals; D002417:Cattle / Q000382:microbiology; D004269:DNA, Bacterial / Q000737:chemistry; D004197:Disease Reservoirs / Q000382:microbiology / Q000662:veterinary*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D005243:Feces / Q000382:microbiology; D005260:Female; D005516:Food Microbiology; D006801:Humans; D008297:Male; D015995:Prevalence; D012756:Sheep / Q000382:microbiology; D022603:Shiga Toxins / Q000096:biosynthesis / Q000235:genetics*; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D013030:Spain / Q000453:epidemiology; D013552:Swine / Q000382:microbiology; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000032:analysis / Q000235:genetics; D015047:Zoonoses
chemical_list: D004269:DNA, Bacterial; D022603:Shiga Toxins; D037521:Virulence Factors