It is supposed to implement the polymerase chain reaction with mix of two pairs of "chromosome" primers "vlm12for'/"IS216rev" and "JS for"/JSrev" species-specific for Y. pestis and Y. psdtbc correspondingly in spot test of plague and pseudotuberculosis. The additional immunodiagnostics is applied to find defective and full-fledged on plague bacteria F1-antigen synthesis in the volume agglomeration reaction and paragglutination with diagnosticums of plasmid-dependent F1 antigen and chromosome FV determined antigen. This mode is characterized by more effectiveness and lesser labor intensiveness. It accelerates the detection of the mix of two agents in bacterial inoculations, organs bioassays and other materials. Also this mode facilitates the analysis of mix cultures of agents of plague and pseudotuberculosis, obtained in "mixed" nidi, the component identification, differentiation and isolation of pure growths of both Yersinia.