FIG. 2.

The PCR detection method is specific for Salmonella and differentiates various typhoid-causing serovars. Colony PCR was performed for different serovars of Salmonella and other pathogenic and nonpathogenic bacteria. Salmonella enterica subsp. arizonae, many Salmonella enterica serovars, and Salmonella bonogori were used. The other pathogenic and nonpathogenic bacteria included Staphylococcus aureus, Escherichia coli, uropathogenic E. coli (UPEC), Shigella flexneri, Yersinia enterocolitica, Hafnia alvei, Vibrio cholerae, Citrobacter freundii, Proteus vulgaris, and Pseudomonas syringae. PCR amplification was performed with the two sets of primers for 30 cycles, and the product was run on a 1.5% agarose gel. The samples have been loaded on the gel in the same order as in Table 1. The 384-bp band is the amplification product of the STY0312 gene of S. Typhi CT18 and its homolog in S. Paratyphi A and is found in both the serovars. The 1,043-bp band is the amplification product of the locus spanning the genes STY0313 to STY0316 and their homologs in S. Typhi Ty2. This locus is absent in S. Paratyphi A. Both these bands are absent in all the other bacterial strains tested.