Detection of Salmonella enterica serovar Typhi (S. Typhi) by selective amplification of invA, viaB, fliC-d and prt genes by polymerase chain reaction in mutiplex format

Aims: Development of a PCR assay that can target multiple genes for rapid detection of Salmonella enterica serovar Typhi (S. Typhi) from water and food samples. Methods and Results: PCR primers for invasion, O, H and Vi antigen genes, invA, prt, fliC-d and viaB were designed and used for the rapid detection of S. Typhi by multiplex PCR. Internal amplification control, which coamplified with prt primers, was also included in the assay. The results showed that all cultures of Salmonella were accurately identified by the assay with no nonspecific amplification in other cultures. The assay had 100% detection probability when a cell suspension of 10(4) CFU ml(-1) (500 CFU per reaction) was used. Salmonella Typhi bacteria were artificially inoculated in the water and food (milk and meat rinse) samples and detected by mPCR after overnight pre-enrichment in buffered peptone water. No Salmonella bacteria could be detected from water samples collected from the field by mPCR or standard culture method. Conclusions: The developed mPCR assay provides specific detection of S. Typhi. Significance and Impact of the Study: Rapid methods for detection of S. Typhi from complex environmental matrices are almost nonexistent. The mPCR assay reported in this study can be useful to identify S. Typhi bacteria in field environmental samples.