Polymerase chain reaction for definitive identification of Yersinia ruckeri

Yersinia ruckeri causes enteric red mouth (ERM) disease in salmonids. Serologic identification of Y. ruckeri is hampered by cross-reactivity with other bacterial isolates of fish origin. Oligonucleotide primers incorporating Y. ruckeri unique sequences were designed to amplify a 409 bp fragment of Y. ruckeri 16S rDNA. The primers did not amplify other genetically related Yersinia or a wide variety of other aquatic or piscine bacteria. This assay provides a rapid, definitive identification of Y. ruckeri that is not subject to the variability inherent in serologic methods.