EVALUATION OF AN AUTOMATED ENZYME-LINKED FLUORESCENT IMMUNOASSAY SYSTEM FOR THE DETECTION OF SALMONELLAE IN FOODS

An automated qualitative enzyme-linked fluorescent immunoassay was com pared to a conventional method outlined in the FDA Bacteriological Ana lytical Manual for the detection of salmonellae in artificially contam inated milk, whey, and carbohydrate-based products. The evaluation par ameters included sensitivity and specificity using purl cultures of Sa lmonella typhimurium, Salmonella tennessee, and Citrobacter freundii a nd mixtures of these species to address the effect of competing microf lora. The overall detection rate of the conventional method was 97% co mpared to a detection rate of 96% for the automated system. The conven tional method sensitivity rate was 97% for the detection of purr cultu res of Salmonella typhimurium and Salmonella tennessee. The automated system sensitivity rate was 96%. The sensitivity rates in the presence of competing microflora for the conventional method and automated sys tem were 96 and 95% respectively. Both the conventional and automated system specificity rates were 100% when challenged with pure cultures of Citrobacter only. Blackburn et al. (Lett. Appl. Microbiol. 19:32-36 , 1994) had previously evaluated the VIDAS (Vitek Immune Diagnostic As say System) Salmonella Assay using pure cultures of salmonellae in lab oratory media. This study addresses the use of the VIDAS for detecting salmonellae when examining complex food matrices.