EVALUATION OF PATHOGENICITY OF NODULE BACTERIA STRAIN RHIZOBIUM LEGUMINOSARUM G 222

Abstract

Objective. Investigate pathogenic (non-pathogenic) properties of a new strain of nodule bacteria Rhizobium leguminosarum G 222. Methods. Microbiological (obtaining a suspension of R. leI guminosarum G 222, determination of its titre by opacity optical standard and by seeding on a digest medium; microscopy of stained imprint smears of internal organs of experimental animals and seeding of tissue samples on a digest medium), pathoanatomical (to determine possible invasiveness and dissemination of bacteria in the tissues of internal organs of animals — in the model of outbred white mice after administration of a suspension of live bacterial cells (oral doses from 0.5 × 109 to 5 × 109 CFU in 0.5 cm3 of sterile isotonic sodium chloride solution per mouse and intraperitoneal doses from 1 × 109 to 5 × 109 CFU/0.5 cm3) and statistical. Results. Over 15 days of observations after administration of a suspension of live bacterial cells, no death of experimental animals was registered. The strain did not lead to any changes in the general condition of the mice. No changes in their behaviour were reported. Fifteen days after the start of the study, it was found that this strain is non-infective (non-invasive), does not disseminate and does not reproduce in the body of experimental animals. Oral and intraperitoneal doses of a suspension of live bacterial cells did not result in bacterial invasion of animal internal organs. No retrocultures were registered. Gross examination did not find characteristic changes in the internal organs of the experimental animals. The obtained results indicate the avirulence of the strain for the studied warm-blooded animals (intraperitoneal LD50 > 5 billion cells/mouse, oral LD50 > 5 billion cells/mouse). Conclusion: According to the results regarding the lack of virulence and according to regulations, the new strain R. leguminosarum G 222 belongs to the group of avirulent microorganisms that are not able to invade the internal organs of studied warm-blooded laboratory animals and can be considered nonpathogenic and used as a basis for microbial preparations to increase crop yields.