[Modification of method of detection virulent Yersinia using crystal violet]

A modified crystal violet method and common agarose medium are proposed for culturing Yersinia before staining. The dish variant is recommended for large quantities and the tube variant for individual strains. Up to 25-30 colonies (plaques) are inoculated into a petri dish and a "dash" inoculation is made into oblique agar in tubes. The cultures are incubated for 24 h at 37 degrees C. After 3-min staining (100 micrograms/ml) of the resultant cultures three phenomena are observed due to the presence of a virulence plasmid with molecular weight of 45-48 megadalton in the strain: violet staining (CV+ test), adhesion to substrate (adhesion+), and adhesion of Yersinia cells to each other (autoadhesion+). Strains with these phenotypical signs are virulent. The proposed method is simple, informative, and reliably detects virulent strains of Yersinia among apathogenic and pathogenic species (variants) isolated from clinical or epidemiologically significant materials.