Phylogenetic analysis of entomoparasitic nematodes, potential control agents of flea populations in natural foci of plague.

Entomoparasitic nematodes are natural control agents for many insect pests, including fleas that transmit Yersinia pestis, a causative agent of plague, in the natural foci of this extremely dangerous zoonosis. We examined the flea samples from the Volga-Ural natural focus of plague for their infestation with nematodes. Among the six flea species feeding on different rodent hosts (Citellus pygmaeus, Microtus socialis, and Allactaga major), the rate of infestation varied from 0 to 21%.

Effect of deletion of the lpxM gene on virulence and vaccine potential of Yersinia pestis in mice.

Yersinia pestis undergoes an obligate flea-rodent-flea enzootic life cycle. The rapidly fatal properties of Y. pestis are responsible for the organism's sustained survival in natural plague foci.

Expression of the plague plasminogen activator in Yersinia pseudotuberculosis and Escherichia coli.

Enteropathogenic yersiniae (Yersinia pseudotuberculosis and Yersinia enterocolitica) typically cause chronic disease as opposed to the closely related Yersinia pestis, the causative agent of bubonic plague. It is established that this difference reflects, in part, carriage by Y. pestis of a unique 9.

Virulence of pPst+ and pPst- strains of Yersinia pestis for guinea-pigs.

Guinea-pigs were infected subcutaneously or by respiratory challenge with plasmid-containing (pPst+pCad+pFra+) Yersinia pestis strain 358 and its pPst-pCad+pFra+, pPst+pCad+pFra- and pPst-pCad+pFra- derivatives, grown in vitro at 28 degrees C or at 37 degrees C. Lack of plasmid pPst did not lead to an increase in LD50 with either route of challenge. When the virulence of the four Y.