Evaluation of a Fluorogenic MPN Procedure for Determining Escherichia coli in Oysters 1.

ABSTRACT

Application of a fluorogenic assay using 4-methylumbelliferone glucuronide (MUG) for detecting Escherichia coli in oysters was not workable due to the presence of an interfering endogenous glucuronidase in the oysters. Modification of the assay by incorporating the MUG into EC broth, rather than LST broth, eliminated the interference. When 25 oyster samples were analyzed for E. coli , 127 of the EC tubes were positive for gas. Of these, 103 were fluorescent and 102 yielded E. coli on isolation. The modification still results in saving approximately 4 d when analyzing for E. coli in oysters.