DNA sequence of a Salmonella-specific DNA fragment and the use of oligonucleotide probes for Salmonella detection.
Hybridization specificity of a 1.8-kb HindIII DNA fragment isolated from Salmonella typhimurium by a molecular cloning technique was confirmed by colony hybridization with 327 Salmonella isolates of various serotypes and 56 non-Salmonella isolates including Enterobacteriaceae closely related to Salmonella, such as Escherichia coli, Klebsiella, Citrobacter and Shigella. It was found that this 1.8-kb DNA fragment was highly specific for all the Salmonella isolates tested. The DNA sequence of this 1.8-kb fragment was then determined by the dideoxynucleotide chain termination method. According to this DNA sequence, six oligonucleotide fragments ranging from 17- to 26-mer were then chemically synthesized and tested for their hybridization specificities. Results show that three of the six oligonucleotide fragments are highly specific for all 327 Salmonella strains tested and can be used as probes for the specific detection of Salmonella in foods or other samples.