Yersinia pestis 201 contains 4 plasmids pPCP1, pMT1, pCD1 and pCRY, but little is known about the effects of these plasmids on the dissemination of Y. pestis. We developed a plasmid-based luxCDABE bioreporter in Y. pestis 201, Y. pestis 201-pCD1+, Y. pestis 201-pMT1+, Y. pestis 201-pPCP1+, Y. pestis 201-pCRY+, Y. pestis 201-p− and Yersinia pseudotuberculosis Pa36060 strains, and investigated their dissemination by bioluminescence imaging during primary septicemic plague in a mouse model. These strains mainly colonized the livers and spleens shortly after intravenous inoculation. Y. pestis 201-pMT1+ appeared to have a stronger ability to survive in the livers, spleens and blood, and to be more virulent than other plasmid-deficient strains. Y. pestis 201-pPCP1+ appeared to have a stronger ability to colonize lungs than other plasmid-deficient strains. Pa36060 has the strongest ability to colonize intestines and lungs. Y. pestis 201 has the strongest ability to survive in blood, and the strongest virulence. These results indicated that the plasmid pMT1 was an important determinant in the colonization of livers, spleens and blood, whereas the plasmid pPCP1 appeared to correlate with the colonization in lungs. The resistance to killing in mouse blood seemed to be the critical factor causing animal death.
