selective amplification of prt, tyv and inva genes by multiplex pcr for rapid detection of salmonella typhi

a multiplex pcr-based assay was developed for detection of salmonella typhi and identification of other salmonella serotypes. three primer-sets were selected from different genomic sequences, malo2-f/malo2-ra primers from invasion gene, parat-s/parat-as as well as tyv-s/tyv-as primers from o-antigen gene cluster of the genus salmonella. this method differentiated salmonella spp., based on size and number of amplified fragments. the salmonella para typhi a and b yielded two bands of 373 bp and 285 bp, respectively, and the other species including s. paratyphi c, s. infantis and s. havana yielded only one 373 bp band. the pcr products of s. typhi and s. enteritidis were 373, 285 and 615 bp. in testing the specificity of the assay, no amplification was observed in non-salmonella species such as shigella, kelebsiella, e. coli, proteus, staphylococcus and streptococcus. the sensitivity of the method was evaluated about 2.5 × 102 cfu/ml, that could be detected by the pcr assay