Serotypes, virulence genes, and intimin types of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) isolated from calves in São Paulo, Brazil.
Shiga toxin-producing Escherichia coli (STEC), is the most important recently emerged group of foodborne pathogens. Ruminants, especially cattle, have been implicated as a principal reservoir of STEC, undercooked ground beef and raw milk being the major vehicles of foodborne outbreaks. Enteropathogenic E. coli (EPEC) strains are defined as eae-harboring diarrheagenic E. coli that possess the ability to form A/E lesions on intestinal cells and that do not possess Shiga toxin genes. In order to determine the occurrence, serotypes and virulence markers of STEC and EPEC strains, 546 fecal samples from 264 diarrheic calves and 282 healthy calves in beef farms in São Paulo, Brazil, were screened by PCR. STEC and EPEC were isolated in 10% and 2.7% of the 546 animals, respectively. Although IMS test was used, the STEC serotype O157:H7 was not detected. The most frequent serotypes among STEC strains were O7:H10, O22:H16, O111:H(-), O119:H(-) and O174:H21, whereas O26:H11, O123:H11 and O177:H11 were the most prevalent among EPEC strains. In this study, serotypes not previously reported were found among STEC strains: O7:H7, O7:H10, O48:H7, O111:H19, O123:H2, O132:H51, O173:H(-), and O175:H49. The eae gene was detected in 25% of the STEC and 100% of EPEC strains. The intimin type theta/gamma2 was the most frequent among STEC, whereas the intimin beta1 was the most frequent intimin type among EPEC strains. To our knowledge, this is the first report of the occurrence of the new intimin muB in one strain of animal origin. This new intimin was detected in one atypical EPEC strain of serotype O123:H? isolated from diarrheic cattle. The enterohemolysin (ehxA) was detected in 51% of the STEC and 80% of the EPEC strains, whereas STEC autoagglutinating adhesin (saa) virulence gene was detected only in those STEC strains negative for eae gene. All 15 bovine EPEC strains isolated in this study were negative for both eaf and bfp genes. Our data shows that in Brazil cattle are not only a reservoir of STEC and atypical EPEC, but also a potential source of infection in humans, since the important STEC serotypes previously described and associated with severe diseases in humans, such as O111:H(-), O113:H21, O118:H16, and O174:H21 were isolated.
Aidar-Ugrinovich L
，Blanco J
，Blanco M
，Blanco JE
，Leomil L
，Dahbi G
，Mora A
，Onuma DL
，Silveira WD
，Pestana de Castro AF
... -
《INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY》
Escherichia coli O157:H7 and non-O157 Shiga toxin-producing E. coli in healthy cattle, sheep and swine herds in Northern Spain.
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.
Oporto B
，Esteban JI
，Aduriz G
，Juste RA
，Hurtado A
... -
《Zoonoses and Public Health》
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