title: Distribution of Shiga toxin genes subtypes in B1 phylotypes of Escherichia coli isolated from calves suffering from diarrhea in Tehran suburb using DNA oligonucleotide arrays.
abstract: OBJECTIVE
  Shiga toxin-producing Escherichia coli (STEC) have emerged as human pathogens and contamination via animal origin has been a major public health concern. We compared the distribution of phylogenetic groups and prevalence of stx gene variants among the pathogenic strains of Escherichia coli isolated from feces of diarrheatic calves in Tehran suburb farms.
  
  
  METHODS
  In this study we screened 140 diarrheatic calves (1-15 days old) for E. coli strains during a 3 months period of time. The isolated strains were grouped into different phylotypes according to the presence of chuA, yjaA and TSPE4.C2 genes. Then, the prevalence of stx gene subtypes was evaluated in the B1 phylotypes.
  
  
  RESULTS
  From diarrheatic calves, 51 bacterial isolates were biochemically identified as E. coli and 31 isolates out of 51 were considered B1 phylotype using DNA Microarray technology. Of these isolates, 20 contained stx1a and stx1b and one harbored all mentioned variants of stx genes except stx2b2 .
  
  
  CONCLUSIONS
  This study showed that in Tehran suburb, the B1 phylotype of E. coli is prevalent as a causative agent of diarrhea in calves and the prevalence of stx1 gene subtypes is dominant in comparison with other subtypes. Considering the possibility that these stx genes can be spread to other strains, bovine E. coli strains are an important source of stx genes for other strains and further study and surveillance seems to be required for the exact identification of virulence profile of E. coli phylotypes in different hosts.
authors.affiliation: Department of Pathobiology, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Staji
authors.affiliation: Istituto Zooprofilattico Sperimentaledell'Abruzzo e del Molise " G. Caporale", Research and Development, Campo Boario, 64100 Teramo, Italy.
authors.forename: Alfreda
authors.initials: A
authors.lastname: Tonelli
authors.affiliation: Department of Pathobiology, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran.
authors.forename: Abbas
authors.initials: A
authors.lastname: Javaheri-Vayeghan
authors.affiliation: Department of Pathobiology, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran.
authors.forename: Emad
authors.initials: E
authors.lastname: Changizi
authors.affiliation: Department of Pathobiology, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Salimi-Bejestani
keywords: B1 phylotype; Escherichia coli; Tehran suburb; calf diarrhea; shiga-like toxin subtypes