Molecular identification of Yersinia ruckeri isolates by polymerase chain reaction test in rainbow trout, Oncorhynchus mykiss

Yersinia ruckeri is a Gram-negative pathogen that causes the enteric redmouth disease, an important systemic fish infection. The aim of this study was to investigate the enteric redmouth disease or yersiniosis caused by Y. ruckeri in rainbow trout farms of Chaharmahal va Bakhtiari Province, in the western part of Iran. For this purpose, we evaluated fishes (8-12 cm in size) that showed clinical signs similar to yersiniosis from 10 farms on the subject of Y. ruckeri existence. At first, the bacteriological and biochemical tests were done, and then polymerase chain reaction (PCR) for detection of isolates was used. Out of 50 evaluated specimens, 3 isolates were Y. ruckeri. PCR was applied to the detection of Y. ruckeri using primer pairs designed for the amplification of 16S rRNA gene fragment. The product of 573 bp was amplified from the DNA extracts of infected organs of suspected fish. DNA sequencing of the PCR products demonstrated specificity of the amplification. This is the first report of molecular identification of Y. ruckeri in this region