Uncommon properties of pLD105 conjugative plasmid.

Plasmid pLD105 isolated from a clinical strain of E. coli determines nitrofuran resistance due to inactivation of low-molecular-weight nitrofuran reductase subunit. pLD105 plasmid belongs to IncF.

[Pathogenicity of Francisella].

The data of literature and the results of the author's research on the pathogenicity of the causative agent of tularemia and other Francisella organisms are reviewed. The solution of the problem of their pathogenicity is based, as stated by the author, on the level of our knowledge of the genetics of Francisella. The conclusion has been made that scientific achievements in the field of the genetics of Francisella, obtained during the last 15 years, make it possible to find out the pathogenicity factors of the causative agent of tularemia, as well as other microbes of the family Francisella.

[Helicobacter pylori and its role in pathology].

The review deals with modern data on the main cultural and biochemical properties, pathogenicity factors and their possible role in pathogenesis. Information on the methods of the diagnostics of diseases associated with H. pylori is given.

[Molecular biological mechanisms of the variability of Helicobacter pylori].

Nowadays notions on the variability of Helicobacter pylori are reviewed. Genetic polymorphism of H. pylori is manifested by variability of gene properties and their order in different strains due to recombinations occurring in these bacteria much more frequently than in other bacterial species.

[Is not plague a "protonosis"? (the role of Protozoa in the epizootiology of plague)].

The author expounds the idea that soil protozoa, whose vegetative forms and cysts can harbor the plague agent for fairly prolonged periods of time, can be a major player in the epizootiology of plague. It is also postulated that the symbiotic protozoa of the digestive tract of rodents and lagomorpha can also be a reservoir of the plague agent. If this is so, among apparent epizootic cycles in mammalians in wild plague foci one should look for Yersinia pestis in the protozoa from the burrows of their primary and secondary carriers.