A total of 39 Vibrio cholerae non O1 non O139 strains were isolated from surface waters of different parts of Dhaka City, Bangladesh. All these strains showed lack of ctx or zot gene, as demonstrated by the PCR analys...A total of 39 Vibrio cholerae non O1 non O139 strains were isolated from surface waters of different parts of Dhaka City, Bangladesh. All these strains showed lack of ctx or zot gene, as demonstrated by the PCR analysis. Eighteen representative strains were tested for enterotoxin production using a rabbit ileal loop model, of which live cells of 8 strains and culture filtrates of 6 strains produced fluid accumulation in ileal loops. However, none of them produced heat stable toxin （ST）, as detected by suckling mouse assay. On the other hand, 15% of isolates produced cytotoxin as detected by the Chinese Hamster Ovary （CHO） cell assay. Fifty times concentrated culture filtrates of the representative strains did not give any precipitin band against the anti-cholera toxin, suggesting the strains produced an enterotoxin, which is antigenically different from known cholera toxin （CT）. Eighty percent of the total isolates were found to be positive for heat labile haemolysin detected by tube method, whereas, 39% were found positive by the Christie-Atkins-Munch-Petersen （CAMP） method. However, 87% of the isolates were positive for haemagglutinin/protease and all of the strains were positive for mannose-sensitive-haemagglutinin assay.展开更多
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A total of 39 Vibrio cholerae non O1 non O139 strains were isolated from surface waters of different parts of Dhaka City, Bangladesh. All these strains showed lack of ctx or zot gene, as demonstrated by the PCR analysis. Eighteen representative strains were tested for enterotoxin production using a rabbit ileal loop model, of which live cells of 8 strains and culture filtrates of 6 strains produced fluid accumulation in ileal loops. However, none of them produced heat stable toxin （ST）, as detected by suckling mouse assay. On the other hand, 15% of isolates produced cytotoxin as detected by the Chinese Hamster Ovary （CHO） cell assay. Fifty times concentrated culture filtrates of the representative strains did not give any precipitin band against the anti-cholera toxin, suggesting the strains produced an enterotoxin, which is antigenically different from known cholera toxin （CT）. Eighty percent of the total isolates were found to be positive for heat labile haemolysin detected by tube method, whereas, 39% were found positive by the Christie-Atkins-Munch-Petersen （CAMP） method. However, 87% of the isolates were positive for haemagglutinin/protease and all of the strains were positive for mannose-sensitive-haemagglutinin assay.
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.
