Isolation, identification, genetic evolution analysis, and pathogenicity test of Riemerella anatipestifer PT-RA1

Abstract:

[Background] Riemerella anatipestifer is a pathogen causing fibrinous pericarditis, perihepatitis, and airsacculitis in ducks. With a variety of serotypes, this pathogen is difficult to be prevented and controlled. [Objective] To understand the genetic characteristics, drug resistance and pathogenicity of Riemerella anatipestifer in Putian city, and provide scientific basis for its treatment and prevention. [Methods] Isolation and purification, 16S rRNA gene identification, and serotype identification were performed on the brain tissue of 15-day-old ducklings suspected to be infected with orrhomeningitis from a breeding farm in Putian. The 16S rRNA gene of this isolate was sequenced, based on which the genetic evolution analysis was performed. Furthermore, the antibiotic resistance of the strain and the pathogenicity to ducklings were determined. [Results] A strain of Riemerella anatipestifer serotype 11 was isolated, named PT-RA1. The 16S rRNA gene of PT-RA1 was in the same branch on the genetic evolution tree as those of the reference strains (GZ-RA12, CZ-RA03, and SD-RA2018) of R. anatipestifer, with 100% similarity, which suggested that R. anatipestifer may have spread across different regions. The isolate was resistant to 15 antibiotics including streptomycin, gentamicin, and kanamycin, while it was sensitive to ampicillin, amoxicillin, cefazolin, ceftriaxone, cefixime, cefepime, tetracycline, doxycycline, oxfloxacin, and florfenicol. The isolate caused a mortality rate of 80% in ducklings, and the dead ducks showed typical symptoms such as fibrinous pericarditis, perihepatitis, airsacculitis, and spleen enlargement of R. anatipestifer infection. [Conclusion] We isolated and characterized a R. anatipestifer strain PT-RA1, which provided a basis for the prevention and control of R. anatipestifer infection and subsequent research.