[The plasmid profile of Yersinia pestis strains in different natural foci of plague in the People's Republic of China].

A total of 159 Y. pestis strains isolated in different geographical regions of China have been studied. Y. pestis isolated in the majority of natural foci of plague in China carry plasmids with molecular weights of 6, 13, 15 and 63 MD. One isolated strain has been found to carry plasmid with a molecular weight of 36 MD. Only a few strains have no plasmids with molecular weights of 6 and 45 MD. In certain geographical zones strains carrying large plasmids of 52 and 92 MD have been detected.