Detection of Salmonella contamination in food samples by dot-ELISA, DNA amplification and bacterial culture.

ABSTRACT

A dot-blot enzyme-linked immunosorbent assay (dot-ELISA) employing a genus Salmonella specific monoclonal antibody (MAb) was used for detection of the bacteria in food samples in comparison with the conventional culture method and the DNA amplification. Among the 200 chicken and pork samples (100 each) tested, 9% and 33%, 7% and 20% and 7 and 23% were positive for salmonellae by the dot-ELISA, the culture method and the DNA amplification, respectively. Statistical analyses revealed that the sensitivity, specificity, efficacy, and positive and negative predictive values of the detection of Salmonella in the food samples by dot-ELISA compared with the culture method were 93.33%, 91.76%, 92%, 66.66% and 98.73%, respectively. Comparison of the DNA amplification and the culture method revealed the sensitivity, specificity, efficacy, and positive and negative predictive values of 100%, 91.58%, 92%, 65.21% and 100%, respectively. The dot-ELISA and the DNA amplification results were in a better agreement when the two assays were compared. The sensitivity, specificity, efficacy, positive and negative predictive values of the dot-ELISA compared to the DNA amplification were 91.3%, 100%, 98%, 100% and 97.5%, respectively. From this study, the dot-ELISA is rapid, simple, sensitive, specific at low cost with limited amount of infectious waste to be disposed and offers another advantage in that it detects only the smooth LPS of Salmonella which implies the possible presence of the virulent organisms.