ABSTRACT
The VIDAS LIS method and the traditional culture methods for detection of Listeria species in food were evaluated in a multilaboratory comparative study. The 6 foods tested were either naturally contaminated or inoculated with 3 different concentrations of Listeria. Results for each food and each contamination level with the VIDAS LIS method were as good as or better than those obtained with the traditional culture method. Of 1558 samples tested, 935 were positive: 839 by the VIDAS method and 809 by standard culture methods. Overall false negative rates were 10.3 and 13.5% for the VIDAS LIS and culture methods, respectively. The false positive rate for the VIDAS LIS assay was 1.4% based on 9 VIDAS LIS positive assays that did not confirm positive by isolation of Listeria. The agreement between the VIDAS LIS and culture methods for all samples tested was 86%.
Subject(s)
Fluorescent Antibody Technique , Food Microbiology , Immunoenzyme Techniques , Listeria/isolation & purification , Animals , Cattle , Culture Media , Dairy Products/microbiology , False Negative Reactions , False Positive Reactions , Fish Products/microbiology , Listeria monocytogenes/isolation & purification , Meat/microbiology , Milk/microbiology , Poultry Products/microbiology , Quality Control , Sensitivity and Specificity , Turkeys , Vegetables/microbiologyABSTRACT
A collaborative study was performed in 27 laboratories to validate the enzyme-linked immunosorbent procedure LOCATE for rapid detection of Salmonella in foods. Results were read visually and with a microtiter plate reader. The LOCATE method was compared with the Bacteriological Analytical Manual (BAM)/AOAC INTERNATIONAL culture method for detecting Salmonella in 6 foods: milk chocolate, nonfat dry milk, dried whole egg, soy flour, ground black pepper, and ground raw turkey. Two foods--dried whole egg and black pepper--required repeat rounds because insufficient data sets were produced initially (AOAC INTERNATIONAL stipulates a minimum of 15 sets per food type). Each laboratory tested one or more of the 6 foods. A total of 1 439 samples were analyzed, and no significant differences (P < 0.05) were observed between LOCATE with either visual or reader detection and BAM/AOAC INTERNATIONAL results. The LOCATE screening method with visual or reader detection is recommended for Official First Action Approval.
Subject(s)
Food Contamination/analysis , Salmonella/chemistry , Animals , Cacao/chemistry , Cacao/microbiology , Eggs/analysis , Eggs/microbiology , Enzyme-Linked Immunosorbent Assay , Flour/analysis , Flour/microbiology , Food Microbiology , Indicators and Reagents , Meat/analysis , Meat/microbiology , Milk/chemistry , Milk/microbiology , Reproducibility of Results , Serotyping , Spices/analysis , Spices/microbiology , TurkeysABSTRACT
A dry-film coliform count plate that is inoculated with 5 mL sample was compared with the Violet Red Bile Agar plate method in a collaborative study by 18 laboratories. Products analyzed were 2% milk, chocolate milk, cream, vanilla ice cream, cottage cheese, and cheese. Collaborators tested blind duplicate uninoculated samples and samples inoculated at low, medium, and high level. Significantly (P < 0.05) higher numbers of coliforms were recovered by the dry-film method from 2% milk samples at the 3 inoculum levels, the chocolate milk at the low- and high-inoculum levels, and the cream at the high-inoculum level. Significantly higher counts were obtained by the agar method for cottage cheese samples at the low-inoculum level. The repeatability standard deviation for the dry-film method was significantly higher for the high-inoculum level chocolate milk sample and the medium-inoculum level cottage cheese. The same statistic was significantly higher for the agar method at all 3 inoculum levels in the 2% milk and the medium-inoculum level cream. The high-sensitivity dry rehydratable film method for enumeration of coliforms in dairy products has been adopted first action by AOAC INTERNATIONAL.
