Drug Resistance and rpoB Gene Mutation of Riemerella anatipestifer Isolated from Diseased Muscovy Ducks

  Objective  Drug resistance and rpoB gene mutation of Riemerella anatipestifer isolated from diseased Muscovy ducks in Putian, Fujian were studied.

  Method  Brain, heart, and liver tissues were aseptically collected from the dead Muscovy ducks that were infected by the disease for isolation, identification, and drug resistance of the pathogen. The genomic DNA of the isolated strains were extracted and the 16S rDNA gene specific primers used for PCR identification. The disk method was applied to test the drug sensitivity of the isolates. The rifampicin resisting region in the rpoB gene was amplified and analyzed.

  Result  Forty-nine strains of R. anatipestifer were isolated to show a broad-spectrum resistance to 11 to 21 kinds of drug, such as, aminoglycosides, macrolides, compound sulfamethoxazole, polymyxin B and rifampicin. But they were highly sensitive to tetracyclines, β-lactams, and florfenicol. In the rpoB gene of 44 rifampicin-resistant strains, a single point mutation, R494K(43/44), and two double point mutations, R494K and V382I (1/44), were found. R494K also existed in one rifampicin sensitive strain.

  Conclusion  It appeared that tetracyclines, β-Lactams, and florfenicol could be the first choice for preventing and treating duck infectious serositis. The single point amino acid mutation location of R494K in the region that determines the rifampicin-resistance could harbor the key to unlocking the mechanisms of the drug resistance of R. anatipestifer.