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Virulence gene profiles and intimin subtypes of Shiga toxin-producing Escherichia coli isolated from healthy and diarrhoeic calves
  1. M. Askari Badouei, DVM, PhD1,
  2. T. Zahraei Salehi, DVM, PhD1,
  3. M. Rabbani Khorasgani, DVM, PhD2,
  4. H. Tadjbakhsh, DVM, PhD3,
  5. G. Nikbakht Brujeni, DVM, PhD1 and
  6. M. G. Nadalian, DVM, DVSc3
  1. Department of Microbiology, Faculty of Veterinary Medicine, University of Tehran, PO Box 14155-6453, Tehran, Iran
  2. Department of Biology, Faculty of Science, University of Isfahan, PO Box 81746-73441 Isfahan, Iran
  3. Iranian Academy of Science, PO Box 19735-167 Tehran, Iran
  1. Correspondence to Dr Zahraei Salehi, e-mail: tsalehi{at}

The virulence properties of Shiga toxin-producing Escherichia coli (STEC) strains isolated from diarrhoeic and non-diarrhoeic calves were compared. The strains were also tested for O157:H7, O111 and O26 serotypes, using PCR and conventional serotyping methods. E coli strains isolated from 297 faecal samples, from 200 diarrhoeic and 97 non-diarrhoeic calves, were screened by multiplex PCR assay for the stx1, stx2, eae and Ehly virulence genes. STECs were recovered from 8 per cent of diarrhoeic calves and 10.3 per cent of non-diarrhoeic calves. The predominant virulence gene profile was stx1/eae/Ehly (47.3 per cent) among isolates from diarrhoeic calves and eae/Ehly (36.8 per cent) among isolates from non-diarrhoeic calves. Among three tested serogroups, the predominant serogroup was O26 (18.4 per cent), and O157:H7 was not detected. Intimin subtyping by restriction fragment length polymorphism analysis revealed only three intimin subtypes (β, γ and θ). A significant difference was observed in the distribution of Int-θ between two groups. Int-θ was present in 50 per cent of the isolates from diarrhoeic calves and in 11.1 per cent of the isolates from non-diarrhoeic calves; this difference was statistically significant (P=0.01).

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