Simultaneous Detection of Aeromonas hydrophila and Edwardsiella tarda by Multiplex PCR in Diseased Catfish.

Diseases represent a serious setback in cultured fish by directly affecting production and causing serious economic losses. Early detection and precise identification of pathogens by polymerase chain reaction (PCR) can help in the selection of preventive and early treatment measures and reduce the losses. In this study, a multiplex PCR assay was demonstrated for simultaneous detection of Edwardsiella tarda and Aeromonas hydrophila. The primer pairs of the major fimbrial subunit (etfA) gene from type I fimbrial gene cluster of E. tarda (415 bp) and cytotoxic enterotoxin (act) gene of A. hydrophila (232 bp) were selected as targets. The multiplex PCR using the target genes simultaneously detected E. tarda and A. hydrophila in different organs (muscle, spleen, liver, and head kidney) of challenged Pangasius pangasius. This method was also capable of simultaneously detecting E. tarda and A. hydrophila in naturally infected catfish, thus indicating mixed bacterial infection in 37.50 % of the diseased population. The results suggested the usefulness of etfA and act genes for the rapid detection of mixed A. hydrophila and E. tarda infection in diseased catfish, irrespective of species. The multiplex PCR method can be useful in commercial aquaculture for performing routine disease diagnosis and detection of these bacterial pathogens. [ABSTRACT FROM AUTHOR]