title: Serotypes, virulence markers and cell invasion ability of Shiga toxin-producing Escherichia coli strains isolated from healthy dairy cattle.
abstract: OBJECTIVE
  The occurrence of virulence markers, serotypes and invasive ability were investigated in Shiga toxin-producing Escherichia coli (STEC) isolated from faecal samples of healthy dairy cattle at Rio de Janeiro State, Brazil.
  
  
  RESULTS
  From 1562 stx-positive faecal samples, 105 STEC strains were isolated by immuno-magnetic separation (IMS) or plating onto MacConkey agar (MC) followed by colony hybridisation. Fifty (47·6%) strains belonged to nine serotypes (O8:H19, O22:H8, O22:H16, O74:H42, O113:H21, O141:H21, O157:H7, O171:H2 and ONT:H21). The prevalent serotypes were O157:H7 (12·4%), O113:H21 (6·7%) and O8:H19 (5·7%). Virulence genes were identified by polymerase chain reaction (PCR). E-hlyA (77·1%) was the more prevalent virulence marker, followed by espP (64·8%), saa (39%), eae (24·8%) and astA (21·9%). All O157:H7 strains carried the γ (gamma) variant of the locus of enterocyte effacement (LEE) genes and the stx2c gene, while the stx1/stx2 genotype prevailed among the eae-negative strains. None of the eae-positive STEC produced the localized adherence (LA) phenotype in HEp-2 or Caco-2 cells. However, intimate attachment (judged by the fluorescent actin staining test) was detected in some eae-positive strains, both in HEp-2 (23·1%) and in Caco-2 cells (11·5%). Most strains (87·5%) showed 'peripheral association' (PA) adherence phenotype to undifferentiated Caco-2 cells. Twenty-five (92·6%) of 27 strains invaded Caco-2 cells. The highest average value of invasion (9·6%) was observed among the eae-negative bovine strains from serotypes described in human disease.
  
  
  CONCLUSIONS
  Healthy dairy cattle is a reservoir of STEC carrying virulence genes and properties associated with human disease.
  
  
  CONCLUSIONS
  Although reports of human disease associated with STEC are scarce in Brazil, the colonization of the animal reservoir by potentially pathogenic strains offers a significant risk to our population.
authors.affiliation: Departamento de Bromatologia, Universidade Federal Fluminense, Niterói, Brasil. aliceg@id.uff.br.
authors.forename: A G M
authors.initials: AG
authors.lastname: Gonzalez
authors.affiliation: Departamento de Microbiologia e Parasitologia, Universidade Federal Fluminense, Niterói, Brasil.
authors.forename: A M F
authors.initials: AM
authors.lastname: Cerqueira
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brasil.
authors.forename: B E C
authors.initials: BE
authors.lastname: Guth
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brasil.
authors.forename: C A
authors.initials: CA
authors.lastname: Coutinho
authors.affiliation: Centro Estadual de Pesquisa em Sanidade Animal, Pesagro-Rio, Niterói, Brasil.
authors.forename: M H T
authors.initials: MH
authors.lastname: Liberal
authors.affiliation: Centro Estadual de Pesquisa em Sanidade Animal, Pesagro-Rio, Niterói, Brasil.
authors.forename: R M
authors.initials: RM
authors.lastname: Souza
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brasil.
authors.forename: J R C
authors.initials: JR
authors.lastname: Andrade
mesh_terms: D000818:Animals; D001938:Brazil; D018938:Caco-2 Cells; D002417:Cattle / Q000382:microbiology*; D004197:Disease Reservoirs / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D006801:Humans; D016133:Polymerase Chain Reaction; D012703:Serotyping; D022621:Shiga Toxin / Q000378:metabolism; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D037521:Virulence Factors; D022621:Shiga Toxin
keywords: Escherichia coli O157:H7; Shiga toxin-producing Escherichia coli; cattle; cell invasion; serotypes; virulence markers