Analysis of virulence factors in Salmonella species

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At present, over 2,000 serovars of Salmonella species have been recorded with bacterial isolates from various laboratories where the antisera against different serovars of Salmonella are available. The identification of bacterial isolates, however, has been so laborious and well-trained personnel are needed even in the already well-established laboratories. In developing countries, it is hard to have a complete set of biochemical and serological materials for the identification of Salmonella. To solve this problem, we constructed the rapid diagnosis system for the detection of virulent Salmonella species by using the polymerase Chain Reaction (PCR) method.Five hundred sixty seven strains of Salmonella with 58 serovars isolated form clinical specimens and food samples were dedicated to the PCR system. As the stn101 and stn111 primers for enterotoxin gene were used to amplify the complementary target DNA in the samples. It was found that all strains have shown the 260 bp specific DNA fra … More gment in the PCR products as demonstrated by 0.0% agarose gel-electrophoresisWhen PCR were performed by using sin106 and sin112 primers for enteroinvasive gene, the expected 378bp DNA fragment were also found in PCR products of all these Salmonella isolates except for one strain of Salmonella serovar Rissen isolated from the patient with gastroenteritis. These specific primers for enterotoxin and enteroinvasive genes did not show any positive result with the other 224 strains of 30 different bacterial species including enteric bacteria. Confirmation of the PCR products by southern blot hybridization test using synthetic oligonucleotide probes which positions corresponded to stn and invA operons have clearly revealed positive reaction and thus, indicated the specific small DNA fragments in the PCR products obtained from the reaction mixture with stn and sin primers.We also produced anti rabbit-serum against Salmonella enterotoxin and constructed the western blotting system for the detection of it. Less