[The specific features of relations of the fleas Xenopsylla cheopis L. to the plague microbe of the Altai subspecies, its L-forms and revertant].

The rate and changes in the formation of bacterial lumps and blocks of the proventriculus in Xenopsylla cheopis fleas in their contamination with the plague microbe of the Altai subspecies, its L-form and revertant were studied to clarify the specific features of relations with the vector, including its transmission ability. The plague microbe of the Altai subspecies, which was exposed to L-transformation in the resistant organism of a warm-blooded host (a guinea pig), as well as L-form revertants obtained on nutrient media substantially lost their ability to get acclimatized in the vector and to form a proventricular block. The capacity to form lumps did not greatly differ in L- and original form of the microbe. At the same time, the ratio of the formed blocks and lumps was much lower, which points to the instability of the formed masses. This is supported by the detection of specimens with partial blocks only among the fleas infected with L-forms. The reversed bacterial form was exceeded in the rate of formation of lumps by the original and L-forms. This may be associated with the reversion of L-forms on the nutrient medium rather than in the vector. At the same time, the revertant formed stable blocks in shorter periods than did L-forms and caused a generalization of the infection in plague-infected mice, which may be important for further transmission of the microbe.