[Crimean hemorrhagic fever in the Rostov region: epidemiological zoning and the activity of natural foci]. / Krymskaia gemorragicheskaia likhoradka v Rostovskoi oblasti: épidemiologicheskoe raionirovanie i aktivnost' prirodnogo ochaga.

The epidemiological zoning of the territory of the Rostov region has been made with the use of the epidemic process patterns and the data indicating the links between the landscape and the natural focus of infection. The spread of infected ticks has been established. The participation of several carrier species in the circulation of Crimean-Congo haemorrhagic fever virus has been confirmed. The mosaic character of their distribution and different levels of their contamination is of great prognostic importance. These data will be used for the improvement of epidemiological surveillance in working out the tactics of epizootological surveys and organization of prophylactic measures.

[Crimean-Congo hemorrhagic fever in Rostov Province: the epidemiological characteristics of an outbreak]. / Krymskaia-Kongo gemorragicheskaia likhoradka v Rostovskoi oblasti: épidemiologicheskie osobennosti vspyshki.

The results of the epidemiological analysis of the outbreak of hemorrhagic fever which was caused by Crimean-Congo hemorrhagic fever virus and occurred during the period of July 3-19, 1999, in the Oblivskaya district of Rostov Province are presented. The specific epidemiological features of the outbreak have been determined. The possible versions of the appearance of the focus of infection and the role of Ixodes ticks in the circulation of the infective agent are discussed.

[Use of aminazine for obtaining isogenic variants of Yersinia pestis strain EV76 with a different set of plasmids]. / Ispol'zovanie aminazina dlia polucheniia izogennykh variantov shtamma Yersinia pestis EV76 s razlichnym naborom plazmid.

A method was elaborated for elimination of plasmids from the plague microbe by aminazine. A set of isogenic derivatives of the vaccine strain Yersinia pestis EV76 with different plasmid profiles has been obtained.

[The sensitivity of bacterial strains of Yersinia pestis isolated from voles to normal human serum]. / Chuvstvitel'nost' shtammov bakterii Yersinia pestis, vydeliaemykh ot polevok, k normal'noi syvorotke cheloveka.

The work deals with the results of the study of the viability of Y. pestis strains, isolated from voles in different natural foci of plague, in human normal serum (HNS) and its dependence on the assimilation of ions of exogenic iron. The cultures isolated at the Transcaucasian mountain focus of infection and having no small plasmid pYP were found highly sensitive to HNS. The introduction of the sources of iron, such as hemoglobin or ferritin, into the serum decreased its bactericidal effect.

[The isolation and characteristics of variant plague microbes not producing the capsular antigen]. / Poluchenie i kharakteristika variantov chumnogo mikroba, ne produtsiruiushchikh kapsul'nogo antigena.

Fifteen stable variants of Yersinia pestis strains exhibiting different degrees of virulence for white mice and guinea pigs were obtained. Multiple passages of the organisms at 37 degrees C in a fluid nutrient medium containing antiplague agglutinating serum were found to be the most efficient method for obtaining noncapsular forms of the plague agent. Acquisition of the Fra(-) phenotype both by wild and laboratory strains was not associated with a loss of the high-molecular plasmid by cells but was probably a result of mutational alterations in the plasmid genes.

[Trimethoprim resistance--a differential trait of strains of Yersinia pestis from a variety of voles]. / Ustoichivost' k trimetoprimu--differentsial'nyi priznak shtammov polevoch'ei raznovidnosti chumnogo mikroba.

Strains of all Y. pestis varieties except for those isolated from voles are highly sensitive to trimethoprim when grown on cultivation media, even when thymidine is added to the medium. The ability to grow on thymidine-containing rich media after trimethoprim addition is a property differentiating Y. pestis variety isolated from voles from the other varieties. These data were confirmed by testing 360 Y. pestis strains obtained from collections of several antiplague institutes and stations of the USSR.

[Iron assimilation by Yersinia pestis on iron-deficient media]. / Izuchenie assimiliatsii chumnym mikrobom zheleza v usloviiakh zhelezodefitsitnykh sred.

The growth of plague bacteria may be limited by the level of iron concentration in the nutrient medium. The virulent strains of the plague microbe possess the more pronounced mechanism of iron assimilation as compared to the vaccine strain. The iron ions are extracted by the virulent and vaccine strains only under the cell surface contact with the iron-saturated transferrin. The iron-sorbing function is peculiar to the plague microbe cell walls which is pronounced more strongly in the virulent strains.