Suppression of cellular immunity factors by toxic fraction of supernatant of broth culture Pasteurella haemolytica

Abstract

In the etiology of many infectious animal diseases, Pasteurella haemolytica belongs to a specific place. An important factor in the pathogenicity of this microorganism, like the Pasteurella multocida serotype D, is the thermostable exotoxin. It can be obtained from bacterial-purified culture fluid. Although the study of toxin formation among microorganisms is quite popular, however, the features of toxin formation in hemolytic pasteurals, depending on the virulence of the pathogen, the nature of the toxic effects of these objects in vivo remain unclear. Materials for research were 16 isolates of Pasteurella haemolytica, isolated from pathological and biological material obtained during the outbreaks of respiratory pathology in farm animals. Initially, the nature of the research concerned the establishment of the potential for toxin formation in the isolates obtained. The method provided for a comparative analysis of the DNA nucleotide sequences of each of the investigated isolates P. haemolytica and information obtained from the international database. Another part of the work concerned the actual allocation of the major groups of toxic components of Pasteurella haemolytica by extraction to determine their biochemical nature. Exotoxin isolation was carried out from the Pasteurella spp. The components of the sediment and supernatant were separated by ion exchange chromatography on TSK gels. In order to detect the harmful effects of toxin hemolytic pasteurals on the body, they used the method of determining the opsonic index (the ratio of the phagocytic number in the mixture without the products of toxic fractions to the mixture with the toxin-containing fraction). It has been established that an important factor of the pathogenetic effect in Pasteurella haemolytica is the toxic fraction. Electrophoregram analysis of the results of DNA amplification in a comparative aspect with the data of standard samples helped to determine the presence of elements of the genome, which indicate the potential for toxin formation in isolated hemolytic pasteurized isolates from the test material. Toxic fractions isolated from Pasteurella haemolytica broth culture supernatant are substances of protein-carbohydrate nature. The isolated peak toxicogenic fractions of dialysate of a bacterial culture sieve contained protein and carbohydrates within the limits of 12.5–20 μg / ml and 0–20 μg/ml, respectively. In the dialysate of the broth culture supernatant, where 5 groups of toxigenic fractions were identified, the content of protein and carbohydrates in them varied, respectively, in the range from 20 to 95 μg/ml and from 3.3 to 26.62 μg/ml. At reproduction of opsono-phagocytic reaction with participation of toxigenic fractions of hemolytic pasteurel, a sufficiently expressed immunosuppressive effect of these complexes on the body of warm-blooded substances with an opsonic index of 3 ± 0.03 was established. During further research it is planned to determine the dermal necrotic and lethal effects of the isolated toxicogenic fractions of hemolytic pasteuride on the body of warm-blooded ones.