DEVELOPMENT AND EVALUATION OF A RAPID TEST PROCEDURE TO DETECT SALMONELLAE IN FEED INGREDIENTS AND FINISHED FEEDS1

Broiler, layer, and swine feeds were inoculated with low levels of three Salmonella serotypes commonly found in feed ingredients using a “charged” chalk. The inoculated feeds, noninoculated control feeds, and naturally contaminated poultry byproduct meals were included in an interlaboratory evaluation of two testing procedures. Three FDA labs, an independent lab, and one university lab were participants in the interlaboratory study. A rapid test kit (Salmonella-Tek, Organon Teknika Corp., Durham, NC) was compared to the culture method of Bailey and Cox (1992) which utilizes Universal Preenrichment broth and standard culture procedures. Each lab utilized 45 100-g feed ingredient or finished feed samples. There was 89.3% agreement in test results by the five labs when comparing the two test procedures. The culture method resulted in 1.3% false negatives while the Salmonella-Tek procedure resulted in 6.2% false positives. Either of the test procedures was capable of detecting extremely low levels (< 5 organisms/100 g) when samples (100 g) were preenriched with Universal Preenrichment broth.