Development and application of specific polymerase chain reaction assay targeting the gyrB gene for rapid detection of Riemerella anatipestifer

A pair of PCR primers was designed and synthesized to amplify a gyrB gene sequence from Riemerella anatipestifer (RA). A fragment of 194 bp was detected in RA-positive isolates, whereas other isolates were negative, which confirmed the high specificity of the primers and PCR conditions. As little as 1.6 x 10(4) cfu/mL of cultural liquid was required by this method. We compared a 16S rRNA sequence-based PCR method and a Biolog bacterial identification system used in the detection and identification of suspicious isolates of RA in clinical tests. The results showed that the gyrB-based PCR was consistent with the results of the Biolog identification system and was more specific. By applying the gyrB-PCR to detect RA strains in 56 duck livers, a positive rate of 46% (26/56) was observed, whereas the positive rate of 85 throat swabs from clinically healthy ducks was 11%. Thus, this method could be used for the epidemiological investigation and preliminary isolate identification of RA.