A comparison of an enzyme immunoassay, DNA hybridization, antibody immobilization, and conventional methods for recovery of naturally occurring salmonellae from processed broiler carcasses

Abstract

Three hundred and ninety raw processed broiler carcasses were obtained from four processing plants and evaluated for the presence of salmonellae by the whole bird rinse procedure. Enzyme immunoassay (Salmonella-Tek™), colorimetric DNA hybridization (GENE-TRAKR), and antibody immobilization (1-2 Test™) methods were compared to the Food Safety Inspection Service (FSIS) culture method for detection of salmonellae. All samples were preenriched in buffered peptone water incubated at 37°C then transferred to and enriched in TT broth (Difco, Detroit, MI) incubated at 42°C for 24 h. After enrichment, manufacturer's instructions were then followed for "rapid" procedures and the FSIS recovery and confirmation scheme was followed for the cultural method. For each sample, if discrepant results were observed between the four procedures, selective plates were streaked from both the TT selective broth and the GN postenrichment broth (Difco). All samples which were positive after initial sampling of TT broth plus additional positive samples from TT selective and GN postenrichment broths were called confirmed cultural positives. Salmonellae were detected on 71% of the carcasses using confirmed cultural procedures and 65% with FSIS culture. Presumptive salmonellae positive samples were found 66, 71, and 76% of the time with the 1-2 Test, GENE-TRAK, and Salmonella-Tek, respectively. As compared to confirmed culture, only 1.4% false positives were observed with the 1-2 Test and GENETRAK, whereas 6% false positives were obtained using Salmonella-Tek. When the false negatives for the four methods were compared to confirmed culture, Salmonella-Tek, GENE-TRAK, 1-2 Test, and FSIS culture had 0.4, 2.5, 7.2, and 8.3%, respectively. The close correlation of these rapid procedures to the conventional procedures warrants consideration of these procedures for detection of salmonellae from broiler chickens.