Rapid detection of Salmonella enterica serovars by multiplex PCR

A multiplex PCR based assay was developed for the identification of the genus Salmonella. Five sets of primers from different genomic sequences such as fimA, himA, hns, invA and hto genes were selected for the identification of serogroups of Salmonella enterica such as S. Typhi, S. ParatyphiA, S. Typhimurium, S. Enteritidis and S. Weltevreden. The selected primers amplified products with the sizes of 85, 123, 152, 275 and 496 bp, respectively, for the genus Salmonella. This assay was found to be highly sensitive, as it could detect 5 cells of Salmonella and 1,000 fg of genomic DNA. Amplification of DNA extracted from other genera viz. V. cholerae and E. coli yielded negative results. This assay provides specific and reliable results and allows for the cost–effective detection of Salmonella in one reaction tube in mixed bacterial communities.     

Development of a multiplex RT-RPA assay for simultaneous detection of three viruses in cucurbits

Begomoviruses and criniviruses, vectored by whiteflies (Bemisia tabaci), are important threats to crops worldwide. In recent years, the spread of cucurbit leaf crumple virus (CuLCrV), cucurbit yellow stunting disorder virus (CYSDV) and cucurbit chlorotic yellows virus (CCYV) on cucurbit crops has been reported to cause devastating crop losses in many regions of the world. In this study, a multiplex recombinase polymerase amplification (RPA) assay, an isothermal technique for rapid and simultaneous detection of DNA and RNA viruses CuLCrV, CYSDV and CCYV was developed. Highly specific and sensitive multiplex RPA primers for the coat protein region of these viruses were created and evaluated. The sensitivity of the multiplex RPA assay was examined using serially diluted plasmid containing the target regions. The results demonstrated that multiplex RPA primers have high sensitivity with a detection limit of a single copy of the viruses. The multiplex RPA primers were specific to the target as indicated by testing against other begomoviruses, potyviruses and an ilarvirus, and no nonspecific amplifications were noted. The primers simultaneously detected mixed infection of CCYV, CYSDV and CuLCrV in watermelon and squash crude extracts. This study is the first report of a multiplex RPA assay for simultaneous detection of mixed infection of DNA and RNA plant viruses.