EVALUATION OF RADIOLABELED AND COLORIMETRIC DNA PROBES IN COMPARISON WITH AN ANTIGEN SCREENING ASSAY FOR THE DETECTION OF SALMONELLA FROM POULTRY FARMS

A total of 48 environmental drag-swab samples from various poultry farms were tested for the presence of Salmonella spp. by culture, an enzyme-linked immunosorbent assay-based Salmonella antigen screening (SAS) assay, and two DNA probes (radiolabeled and colorimetric). The radiolabeled DNA probe was allowed to hybridize with culture-positive samples (n = 8) and was found to detect Salmonella spp. in all cases (100%). Both of the probes, subsequently hybridized with culture-negative samples (n = 8), were observed to yield good agreement (91%) with the culture findings. The remaining samples (n = 32) were tested by the SAS assay, and where there was no agreement between the culture and SAS, samples were further examined by the DNA probes. Results using both probes agreed with those obtained by culturing the samples but did not agree with the SAS assay result when the ratio of samples tested to samples positive (S/P) cutoff value used was 0.5.