The distribution of invA, pagC and spvC genes among Salmonella isolates from animals

New molecular diagnostic techniques often rely on hybridization or amplification of specific DNA regions to detect pathogenic bacteria. The choice of genes to be used as probes or as the targets of amplification techniques is critical to the success of these procedures. The genes so used might best be those associated with virulent isolates and having a wide distribution among such isolates. In this study three genes, invA, pagC and spvC, thought to be associated with the virulence of salmonellae, were labelled and used to probe the total DNA from 103 Salmonella isolates from animals in an attempt to determine whether these genes might be useful in diagnostic procedures. pagC was detected in 99% of the Salmonella tested, and invA was detected in 94.2% of the isolates. Both pagC and invA were detected with a significantly higher frequency than spvC in isolates from chickens and swine, but no significant difference in detection of these three genes occurred when bovine isolates were examined. Failure to detect any of these genes occurred in only one isolate. Isolates from apparently healthy or from clinically ill chickens and swine could not be distinguished by detecting these three genes. The genes were not detected in the non-Salmonella strains tested. These results suggest that, of these three genes, pagC may be the best choice for use as a probe or polymerase chain reaction target in future detection protocols.