Escherichia coli O157:H7 and Non-O157 Shiga Toxin-producing E. coli in Healthy Cattle, Sheep and Swine Herds in Northern Spain

• Published in: Zoonoses and public health 2008-03, Vol.55 (2), p.73-81
• Main Authors: Oporto, B., Esteban, J. I., Aduriz, G., Juste, R. A., Hurtado, A.
• Format: Article
• Language: English
• Subjects: Animal diseases; Animals; Cattle; Cattle - microbiology; Disease Reservoirs - microbiology; Disease Reservoirs - veterinary; DNA, Bacterial - chemistry; E coli; Escherichia coli Infections - epidemiology; Escherichia coli Infections - transmission; Escherichia coli Infections - veterinary; Escherichia coli O157 - genetics; Escherichia coli O157 - isolation & purification; Escherichia coli O157 - pathogenicity; farm; Feces - microbiology; Female; Food Microbiology; Hogs; Humans; Livestock; Male; PCR; Prevalence; Sheep; Sheep - microbiology; Shiga Toxins - biosynthesis; Shiga Toxins - genetics; Shiga-Toxigenic Escherichia coli - genetics; Shiga-Toxigenic Escherichia coli - isolation & purification; Shiga-Toxigenic Escherichia coli - pathogenicity; Spain - epidemiology; STEC; swine; Swine - microbiology; Toxins; Virulence - genetics; Virulence Factors - analysis; Virulence Factors - genetics; Zoonoses
• ISSN: 1863-1959; 1863-2378
• DOI: 10.1111/j.1863-2378.2007.01080.x

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) (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 stx1, stx2, eaeA and E‐hlyA 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 stx2 gene‐positive, eaeA was detected in 95.9%, and the toxigenic profile stx2/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. stx2 was predominant in non‐O157 isolates from cattle, whereas in sheep the combination stx1/stx2 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.