Changes in the Organs of Experimental Animals in the Dynamics of the Infectious Process Caused by Bacillus Anthracis with Different Plasmid Profiles

Background. The current direction is the study of anatomical and histological changes caused by the causative agent of anthrax with a different plasmid profile. It was found that Bacillus anthracis strains with the same set of plasmids and the same morphological, serological and cultural properties sometimes have different pathogenicity.

Aim of the study. Comparative analysis of anatomical and histological changes in the organs of experimental animals in the dynamics of the infectious process caused by the pathogen B. anthracis with different genotypes.

Methods. Four strains were used as the study object: B. anthracis I-275 (pCO1^–/ pCO2^–), B. anthracis I-323 (pCO1^–/ pCO2^–), B. anthracis I-217 (pCO1⁺/pCO2^– and B. anthracis 34F Stern pCO1⁺/pCO2^–). The study was conducted on 260 certified white mice. Histological material was embedded in paraffin, semi-thin sections were stained with hematoxylin-eosin, thionine, and according to Brachet. The severity of pathological changes, the presence of the pathogen, and the proliferation of plasma cells were evaluated. The changes detected during the autopsy of the animal and the results obtained during the histological examination of the anatomical material were analyzed and generalized. Microphotography and quantitative analysis of plasma cells were performed using the “Motic Images Plus 2.0” application software package. Statistical processing of the obtained data was performed using the computer program “Statistics”, version 6 (Novosibirsk). The results were considered reliable if the probability of error was less than 0.05 (p < 0.05) in relation to the control.

Results. Differences in anatomical and histological changes in organs and tissues of white mice infected with B. anthracis with the same set of plasmids were revealed. It was found that in animals infected with non-plasmid strains of B. anthracis, the proliferation of plasma cells is significantly reduced compared to animals infected with singleplasmid strains of the anthrax pathogen.

Conclusion. The obtained data suggest that the revealed differences are related to the plasmid profile of the studied strains, but also to the peculiarities of their enzymatic activity, adhesion ability, and other factors. Thus, anthrax strains that have the same morphological, serological and cultural properties sometimes have different virulence. And also, anthrax strains that have lost virulence lose their immunogenicity, as evidenced by the ratio of plasma cells.

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