Enterohaemolysin production and verotoxin genes in Esche-richia coli strains isolated from neonatal calves in India

摘要

Objective:To screened all haemolytic strains of Escherichia coli (E.coli)for the presence of verotoxin genes and speculate the association between enterohaemolysin production and presence of verotoxin genes.Methods:A total 176 of E.coli strains of 64 serogroups isolated from neonatal calves were selected and screened for al-pha-haemolysin and enterohaemolysin production on sheep blood agar and 5% washed sheep blood agar.Two types of haemolytic strains were further characterized by PCR for presence of Verotoxin gene (VT1 and VT2) and confirmed by verocell cytotoxicity assay.Results:Among 27 enterohaemolytic positive strains,19 (70. 37%)strains were found positive for presence of verotoxins (VTs)gene and verocell cytotoxicity assay. Whereas 34 alpha-haemolysin strains were found negative for VTs.Eight strains of E.coli were found VTs neg-ative but Ehx positive.Conclusion:The close association between enterohaemolysin production and presence of verotoxin genes makes it useful epidemiological marker for rapid screening of Verotoxic E.coli but this pheno-typic marker for screening of verotoxigenic Escherichia coli(VTEC)alone may raise a question in animal.