Development of a PCR Assay for the Identification of Salmonella Thompson

The effective control of foodborne salmonellosis relies on the rapid and reliable detection and identification of the pathogen. Reliable detection tools for identifying the most common Salmonella serovars should translate to a considerable alleviation of the health burden attributed to Salmonella. We have developed a PCR assay for the rapid identification of colonies of Salmonella enterica serovar Thompson, a common serovar. Genomic analyses of publicly available sequences of Salmonella Thompson revealed the presence of a unique, Thompson-specific fragment, which we have used to design a pair of oligonucleotides, STho-F and STho-R, for the PCR amplification of an 808 bp DNA fragment. Using crude DNA extracts, the 808 bp fragment was detected in 77 out of 78 isolates of S. Thompson (sensitivity = 98.7% n = 78 isolates) but not in any of the non-Salmonella organisms tested (n = 100; 100% specificity) nor in non-Thompson Salmonella serovars (n = 100; 100% specificity). The sensitivity (inclusivity) and specificity (exclusivity) indices of the PCR assay for S. Thompson met the standard regulatory requirements. The Thompson primer pair was compatible with other primers pairs in a multiplex PCR designed for three other common Salmonella serovars. Colonies belonging to the Enteritidis serovar (n = 100), Heidelberg serovar (n = 100), Typhimurium serovar (n = 100), and Thompson serovar (n = 77) were correctly designated, indicating excellent inclusivity and exclusivity scores for all four Salmonella serovars tested in a single multiplex PCR.