Field evaluation of the membrane filter-disc immunoimmobilization technique in the detection of salmonellae in egg products.

The membrane filter-disc immunoimmobilization (MFDI) technique was found to more sensitive than the official US Department of Agriculture (USDA) method for the detection of salmonellae in unpasteurized egg whites, unpasteurized whole eggs, pasteurized dried eggs and pasteurized whole egg samples examined at two processing facilities over a period of 18 months. Of 70 samples of unpasteurized egg samples examined, 39 were positive for Salmonella by the official USDA method while 54 were positive by the MFDI method. All positive samples by the MFDI technique were confirmed by subculturing on differential plating media and by performing biochemical and serological tests on the isolates. Of 67 pasteurized liquid whole egg and dried egg white samples examined, all were negative for Salmonella by the USDA method while Salmonella was isolated by the MFDI technique from one sample of pasteurized whole egg product.