COMPARISON OF BETA-GLUCURONIDASE AND INDOLE-BASED DIRECT PLATING METHODS FOR ENUMERATING ESCHERICHIA-COLI IN ARTIFICIALLY INOCULATED GROUND MEATS

Peptone tergitol glucuronide (PTG) agar containing 4-methylumbelliferyl-β-D glucuronide (MUG) (for β-glucuronidase activity), the Holbrook, Anderson, Baird-Parker (HABP) method (for detecting indole production), and the standard 3-tube most probable number (MPN) method were compared with plate count agar (PCA) for enumerating three strains of unstressed Escherichia coli artificially inoculated into ground beef and chicken at 1-6 × 106 cells/g. No significant difference (P>0.05) was determined between PTG agar and PCA in the recovery of E. coli. The MPN method enumerated a significantly greater (P<0.05) number of E. coli cells than PCA. Compared with PCA, the HABP method recovered a significantly lower (P<0.05) number of E. coli cells from chicken, whereas no significant difference (P>0.05) was obtained with ground beef. When combining all data from chicken and beef, the recovery of E. coli cells by the HABP method was also significantly lower (P<0.05). Overall, based on the enumeration of E. coli on PCA, the HABP method, PTG agar, and MPN method recovered 57, 102, and 144%, respectively. Copyright © International Association of Milk, Food and Environmental Sanitarians.