Development of Methodological Approaches and Criteria to Classify Yersinia pestis Training Strains as an Agent of Pathogenicity (Hazard) Group III

Abstract

Objective of the study was to select the criteria and methodological approaches to reclassify avirulent strains of plague agent from pathogenicity (hazard) group I into pathogenicity group III. Materials and methods . We have reviewed domestic and foreign normative, methodological documents, scientific publications in the field of laboratory diagnostics of plague and biosafety provision while working with pathogenic biological agents. Results and discussion. A complex of criteria for reclassification of Y. pestis strains from hazard group I into hazard group III has been substantiated; the methods for their assessment identified. Validation has revealed the grounds for reassignment of a number of avirulent Y. pestis strains included into the training kit which is compiled for mastering the training module “Microbiology and laboratory diagnostics of plague” into pathogenicity group III. We have demonstrated the feasibility of combining the structured methods of assessment of pathogenic properties in plague microbe with additional informative ones; in particular, evaluation of cytotoxicity of Y. pestis strains in relation to leucocytes of whole human blood in vitro. Analysis of a strain virulence should be built on complex characterization of major pathogenicity factors using advanced molecular-genetic research methods, the data on phenotypic manifestations of their functioning, as well as the level of pathogenicity for sensitive laboratory animals. The review of the utilized quantitative indicators for differentiation of plague microbe strains by virulence taking into account LD50 values for Y. pestis EV NIIEG strain is a relevant task. It is practical to supplement the complex approach with informative research methods, notably, characterization of strain cytotoxicity which shows high correlation with virulence criterion LD50.