[SPECIFIC FEATURES OF RELATIONSHIPS BETWEEN THE FRONTOPSYLLA LUCULENTA LUCULENTA (JORDAN ET ROTHSCHILD, 1923) FLEA AND THE PLAGUE PATHOGEN WITH DIFFERENT PLASMID COMPOSITION].

It was experimentally established that plague pathogen strains with different plasmid composition variously suppressed the viability of Frontopsylla luculenta luculenta fleas. Dead insects were most frequently observed among those infected with a virulent strain having the cryptic plasmid pTP33. The presence of the avirulent and apesticinogenic plasmid I-3480 in the fleas less deteriorated their state.

[The sensitivity of plague agent from Siberian natural focuses of disease to antibacterial preparations in vitro].

The comparative analysis was applied concerning antimicrobic action of different groups of antibacterial preparations on the plague agent strains isolated from Siberian natural focuses of disease. The analysis was applied to results obtained using such different methods as disco-diffusive technique, serial dilution and HiCOMB MIC test. It is established that freshly isolated cultures of Yersinia pestis have high sensitivity to antibacterial preparations of different groups.

[Host influence on the frequency of block formation in males and females of Citellophilus tesquorum altaicus Ioff, 1936 (Siphonaptera: Ceratophyllidae) and transmission the plague pathogen by these fleas].

Data obtained during feeding of Citellophilus tesquorum aitaicus Ioff, 1936 infested females and males (Siphonaptera: Ceratophyllidae), the main vectors of plague in Tuva natural plague locus, on the natural host and laboratory animal was analyzed. It was found that sexual differences in fleas depended on the type of the host. Females fed more actively on the longtailed ground Citellus undulatus than on white mouse.

[Interaction of plague microbe strains varying in plasmid composition with the fleas Xenopsylla cheopis (Roths. 1903)].

The interaction of two Yersinia pestis strains varying in plasmid composition with the fleas Xenopsylla cheopis was studied. The reference virulent strain I-2638 having four plasmids (pCad, pPst, pFra, and pTP 33) and its selected avirulent strain I-3480 that had lost the plasmids pCad and pPst formed a proventricular block in the fleas with equal frequency. There were no differences in the block-forming capacity of these strains among the infected females; however, the stock strain was more active in blocking the proventriculus in females in spring than was the mutant one.