Hydrophobic grid membrane filter/MUG method for total coliform and Escherichia coli enumeration in foods: collaborative study.
Twenty-four laboratories participated in a collaborative study to validate a hydrophobic grid membrane filter (HGMF) method incorporating the use of 4-methylumbelliferyl-beta-D-glucuronide (MUG) for enumeration of total coliform and Escherichia coli bacteria in foods by comparing its performance against the AOAC 3-tube MPN method (46.013-46.016). Raw milk, raw ground poultry, whole egg powder, cheese powder, and ground black pepper were included in the study. The total coliform methods did not differ significantly, except that the 3-tube method detected a significantly higher level of total coliforms than did the HGMF method in the ground black pepper. Conversely, the HGMF/MUG E. coli method detected significantly higher numbers of E. coli present in the egg powder, cheese powder, and ground black pepper samples, while not differing significantly from the 3-tube method for the raw milk and raw ground poultry samples. The overall confirmation rate of MUG-positive colonies isolated using the HGMF method was 99.5%. The hydrophobic grid membrane filter/MUG method has been adopted official first action as an additional method to AOAC official final action method 46.030-46.034.
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QA Laboratories Ltd, Toronto, Ontario, Canada.
D000818:Animals; D002417:Cattle; D002611:Cheese / Q000032:analysis; D002645:Chickens; D003212:Condiments / Q000032:analysis; D004531:Eggs / Q000032:analysis; D004926:Escherichia coli / Q000302:isolation & purification*; D005374:Filtration; D005516:Food Microbiology; D007202:Indicators and Reagents; D008460:Meat / Q000032:analysis; D008892:Milk / Q000382:microbiology; D013056:Spectrophotometry, Ultraviolet
D007202:Indicators and Reagents