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Escherichia coli O157:H7 and Non‐O157 Shiga Toxin‐producing E. coli in Healthy Cattle, Sheep and Swine Herds in Northern Spain
Author(s) -
Oporto B.,
Esteban J. I.,
Aduriz G.,
Juste R. A.,
Hurtado A.
Publication year - 2008
Publication title -
zoonoses and public health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.87
H-Index - 65
eISSN - 1863-2378
pISSN - 1863-1959
DOI - 10.1111/j.1863-2378.2007.01080.x
Subject(s) - herd , escherichia coli , biology , shiga toxin , immunomagnetic separation , microbiology and biotechnology , polymerase chain reaction , feces , macconkey agar , dairy cattle , beef cattle , virulence , veterinary medicine , gene , zoology , medicine , genetics
Summary 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) ( rfb E and fli C 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 , eae A and E‐ hly A genes. Both immunodetection methods showed a moderate–good level of agreement (κ = 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, eae A was detected in 95.9%, and the toxigenic profile stx 2 / eae A/E‐ hly A was present in 75.5% of the isolates. Among the non‐O157 STEC, prevalence of eae A was significantly lower (5.3%) and E‐ hly A was present in 50.2% of the isolates but only sporadically associated with eae A. 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.