Biological properties and genetic characteristics Ornithobacterium rhinotracheale in vivo и in vitro

The aim of this study was to select the optimal algorithm for working with the Ornithobacterium rhinotracheale OR-21 strain, which is promising for use as a production strain for the manufacture of a vaccine against ornithobacteriosis in birds, based on the study of its biological properties, virulence, and genetic characteristics after a series of its passages on nutrient media and SPF chicken embryos. When selecting nutrient media, growth additives, and cultivation conditions for the strain, the composition, sensitivity, inhibitory and differential properties of the media used, the growth rate, and the preservation of the stability of the biological properties of the cultured microorganism were taken into account. When selecting nutrient media, growth additives, and cultivation conditions for the strain, the composition, sensitivity, inhibitory and differential properties of the media used, the growth rate, and the preservation of the stability of the biological properties of the cultured microorganism were taken into account. In experiments on conducting passages of O. rhinotracheale OR-21 strain cultures, 5–7- day old chicken embryos were used as a laboratory model in vivo. The virulence properties were assessed on laboratory animals using generally accepted methods. In the experiments, Russian White chickens were used as a laboratory model. In the process of choosing a laboratory model for conducting passages, it was found that chicken embryos are highly sensitive to the studied strain and allow obtaining a higher concentration of Ornithobacterium rhinotracheale OR-21 microbial cells, compared to passages on nutrient media. In addition, the use of SPF chicken embryos, unlike poultry, made it possible to exclude contamination with foreign microflora during passages. 2207 genes were identified for O. rhinotracheale. No differences were found when comparing the genomes of cultures of passages 1 and 10. The highest homology of the isolate after 10 passages is observed with the typical strain O. rhinotracheale DSM 15997. It was found that, on nutrient media, the maximum number of passages of the strain culture is limited to 6 transfers, while on chicken embryos, the causative agent of ornithobacteriosis continues to multiply, but loses virulence in relation to them and 240-day-old chickens. The loss of virulence does not affect other biological properties of the strain.