ASSOCIATION OF ENTEROHEMOLYSIN AND NON-FERMENTATION OF RHAMNOSE AND SUCROSE WITH SHIGA-LIKE TOXIN GENES IN ESCHERICHIA-COLI FROM CALVES

Fecal Escherichia (E.) coli strains from calves were tested for simply detectable phenotypical features associated with Shiga-like toxin (SL T) genes. DNA hybridization with SLT-specific oligonucleotide gene pro bes (detection of genes for SLT-I and SLT-II) was the ''gold standard' ' for the evaluation of Vero cell cytotoxicity, fermentation of severa l saccharides, beta-D-glucuronidase activity and production of alpha-h emolysin (alpha-Hly) or enterohemolysin (E-Hly).While SLTEC and non-SL TEC did not significantly differ in production of alpha-Hly, beta-D-gl ucuronidase activity and fermentation of D-sorbitol, production of E-H ly and non-fermentation of L-rhamnose (Rha) and D-sucrose (Sue) were a ssociated with SLT genes. Sensitivity and specificity of the E-Hly(+) phenotype were 53% and 88% for identification of calf SLTEC. When thre e markers were combined to form the parameter [''E-Hly(+) or (Rha(-) a nd Suc(-))''], sensitivity was higher (65%) and specificity was almost the same (85%). Production of enterohemolysin and inability to fermen t rhamnose and sucrose were more often associated with the SLT-I gene than with SLT-II genes. Approximately 71% SLT-I+ E. coli were positive in the enterohemolysin assay. The test combination ''E-Hly(+) or (Rha (-) and Suc(-))'' was most valuable for the presumptive identification of SLT-I+ E. coli (sensitivity 85%, specificity 83%). These data sugg est that the phenotype ''E-Hly(+) or (Rha(-) and Suc(-))'' may be a he lpful marker for the detection of SLT-I+ E. coli in SLTEC associated d iarrhoea of calves.