[Extracellular resistance of Yersinia pestis to phagocytosis]

The authors were the first to perform stimulation of parasitizing condition of plague bacilli in mammalian bloodstream by addition of adequate quantity of glucose and calcium ions into the routine bacteriological medium, as well as growing the plague agent in RPMI-1640, isotonic to the serum of man and mammals susceptible to plague. Comparison of proliferative, phenotypic, and biochemical properties of fully virulent and vaccine Y. pestis strains demonstrated the advantages of RPMI-1640 medium, which provided extensive in vitro multiplication of the mentioned microorganisms similar to the bacterioemic stage of plague. Using methods of molecular microbiology and immunology, including a panel of monoclonal antibodies, the researchers demonstrated an abrupt fall of production of main plague surface species-specific antigens such as F1, 'murine' toxin/phospholipase D and fibrinolysin, followed by inhibition of biochemical activities associated with these antigenic substances in Y. pestis, as well as specific components of lipopolysaccharide. Possible molecular mechanisms of virulence and adaptive variability of plague bacteria in the extracellular conditions in mammalian organism are discussed.