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...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 alpha -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 negative 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 phenotypic marker for screening of verotoxigenic Escherichia coli(VTEC) alone may raise a question in animal.展开更多
文摘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 alpha -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 negative 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 phenotypic marker for screening of verotoxigenic Escherichia coli(VTEC) alone may raise a question in animal.
