AN EVALUATION OF THE USE OF 4-METHYLUMBELLIFERYL-BETA-D-GLUCURONIDE (MUG) IN DIFFERENT SOLID MEDIA FOR THE DETECTION AND ENUMERATION OF ESCHERICHIA-COLI IN FOODS

The use of 4-methylumbelliferyl-beta-D-glucuronide (MUG) in different solid media for the detection and enumeration of Escherichia roll in f oods was evaluated by; testing the effects of different substrate conc entrations (50 or 100 mu g ml(-1)), incubation temperatures (37 or 41. 5 degrees C) and incubation times (8, 12, 24 and 48 h). Different kind s of foods, both naturally and artificially contaminated, were analyse d. The use of selective media without differential substances and an i ncubation time of 24 h Seem to be worthy of recommendation. In this ca se an incubation temperature of 37 degrees C would be preferred and th e MUG concentration could be reduced to 50 mu g ml(-1). Incubation tim es: shorter than 24 h, which may cause a loss of sensitivity, require higher incubation temperatures (41.5 degrees C) and MUG concentration (100 mu g ml(-1)).