The glycolipids of the causative agent of tularemia]

Up to 10 glycolipids were detected in F. tularensis with the use of thin-layer chromatographic techniques. These glycolipids were slime antigens of F. tularensis membrane. Attenuated F. tularensis strains were found to have defects in their glycolipid composition: in the vaccine strain glycolipid 8 was replaced by more polar lipid 8-a; the avirulent strain had only two glycolipids, and one of them was not typical for virulent strains. Considering that glycolipids differed from entero-bacterial Vi-antigen in their physical-chemical and biological properties, the suggestion was made that the use of the symbol "Vi" to denote the surface substances of F. tularensis should be abolished.     

Geographical race typing of the causative agent of tularemia using antibiotics]

Reaction of the strains of the tularemia causative agent to erythromycin (100 gamma/ml) or oleandomycin (400 gamma/ml) is one of the taxonomic tests. The study of 82 strains of the holarctic race and 63 strains of the Central Asiatic race according to this test showed that the strains of the holarctic race were divided with respect to these macrolides into sensitive (biotype I) and resistant (biotype II). The strains of the both races were isolated at the territory of the Kazakh SSR. Such a reaction of the strains of the holarctic race is a stable feature and is not connected with virulence, the isolation source and the biochemical properties of the strains. Division of the holarctic race into the biotypes (I and II) with respect to erythromycin and oleandomycin may be of definite significance in epidemiological and epizootological examination for tularemia with a purpose of determining the source of the infection, as well as in defining the borders of the infection focus area with circulation of this or that biotype of the holarctic race of the tularemia causative agent.     

Mechanism of the changes in the animal reactivity to tularemia in mixed infection]

Experiments were conducted on albino rats infected with listeria or salmonelloses, and then with tularemia; differences were revealed in the duration of manifestation of nonspecific resistance associated with peculiarities of pathogenesis and immunogenesis of the background infections. One of the significant factors causing an increase of albino rats resistance to tularemia in mixed infection was activation of the immunomorphological reaction promoting accelerated development of specific immunity reactions to this infection.     

Preservation of the causative agent of tularemia in the external environment in eastern Taimyr]

Strains of the causative agent of tularemia were for the first time isolated by the authors from the objects of the external environment in the tundra zone of Eastern Taimir; this indicates a possibility of preservation of the microbe under conditions of the extreme north.     

Isolation of the causative agent of tularemia from Siberian lemmings in Eastern Taymyr]

The authors present the results of bacteriological and serological study for tularemia of 498 lemmings caught in Taimyr. Positive results were revealed in 4 out of 98 sera examined in the indirect hemagglutination test. In carrying out 67 biological tests on albino mice there were isolated for the first time in the Soviet Union 6 cultures of the causative agent of tularemia from the spleen of lemmings. By morphological, cultural and virulent properties the cultures obtained failed to differ from those isolated in other regions of the Soviet Union, and, consequently, we referred to the holoarctic race. Thus, it was established by the authors (both serologically and bacteriologically) that there existed tundra foci of tularemia.     

Diminution of the antibacterial activity of antibiotics in cultures and in experimental mixed infections]

We have studied interactions between Staphylococcus aureus and Pseudomonas aeruginosa in the absence and the presence of four different antimicrobials in mixed cultures and experimental infections. These two bacterial species, in addition to having different properties, are known to be opportunistic pathogens often present in human microflora. Two main aspects have been investigated and they are related to modifications in two species affecting their equilibrium in the mixed bacterial population and also their pathogenicity markers. Our results indicate that individual growth of S. aureus and P. aeruginosa is not modified in vitro in mixed cultures in the absence of antimicrobials; in vivo, in mouse peritoneal cavity, there is a synergism favorable to S. aureus. In the presence of rifamycin SV and three cell wall inhibitors, pencillin G,D-cycloserine, and vancomycin, we have observed that P. aeruginosa protected S. aureus against the inhibitory effect of these antimicrobials in vitro and in vivo. Such results were obtained in different conditions of culture, stationary, shaken, and in special apparatuses, an "Ecologen" and a "Chemostat." When any one of the antimicrobials was allowed to be in contact for 6 to 8 h with P. aeruginosa cells in a culture, we observed a decrease in their inhibitory effects against S. aureus. These results were supported by microscopical observation. It seems that the inhibitory effects of the antimicrobials have hindered the formation of toxic products of S. aureus, e.g., alpha toxin, and that it was not restored in the presence of P. aeruginosa. Conversely, P. aeruginosa remained apparently unchanged through all these experiments. Our observations may imply that the inhibitory effect of an antimicrobial towards a bacterial species may be significantly decreased in the presence of another species, sometimes present in human microflora.     

An experimental study of mixed tularemia and Omsk hemorrhagic fever infection in muskrats]

Musk-rats were infected simultaneously and at three-day interval with tularemia and Omsk hemorrhagic fever (OHF); the course of this mixed infection under the mentioned conditions were studied. Virological, microbiological and morphological data indicated that infection of musk-rats with OHF and tularemia caused development of mixed infection in them. A more severe course of mixed infection was associated with enhanced vascular affections caused by the action of the OHF virus. An inhibition of tularemia caused by the OHF development was noted in the course of mixed infection.     

Sensitivity of the causative agent of tularemia to antibiotics

Sensitivity of the tularemia causative agent of different geographical races to antibiotics such as streptomycin, tetracycline, gentamicin, rifampicin (20 strains), ampicillin, polymyxin M, erythromycin, oleandomycin (361 strains) and lincomycin (294 strains) was studied. High sensitivity of the tularemi a microbe to streptomycin, tetracycline, rifampicin (MIC of 10 gamma/ml), gentamicin (MIC of 1 gamma/ml) and resistance to 50 gamma of ampicillin and 1000 gamma/ml of polymyxin M were found. Combined use of 50 gamma of ampicillin and 100 gamma/ml of polymyxin M added to the nutrient medium for growth inhibition of the foreign flora on isolation of the tularemia causative agent from the infected material including stable laboratory animal carcases was recommended. Marked differences in sensitivity of the strains of different geographical races to the macrolides and lincomycin were observed. The strains of the non-Arctic and Central Asiatic races were of low resistance to the above drugs (the MIC of erythromycin, oleandomycin and lincomycin were 10--50, 50--400 and 25--100 gamma/ml respectively. Within the holarctic race 40 per cent were low resistant and 60 per cent were highly resistant to these drugs. The above drugs should not be used for treatment of tularemia cases.     

Effect of prodigiozan on the phagocytic activity of the leukocytes in melioidosis intoxication]

In development of experimental melioidosis intoxication, the activity of the mechanisms controlling non-specific immunological reactions changed that was evident from changes both in the quantitative and qualitative indices of phagocytosis. The absorption function of the neutrophils was lowered during 2 days from the moment of administration of acetone killed bacterial mass of the melioidosis causative agent which was evident from decreased percentage and index of phagocytosis as compared to the control animals. The qualitative index of the digestive capacity of the neutrophils, i.e. the index of phagocytosis completeness was also low for 7 days of the experiment. The positive role of prodiglozan in activation of the host protective forces in cases with meliodosis intoxication was shown. Prodigizan administered 48 hours before injection of the bacterial mass of the melioidosis causative agent stimulated both the absorption and digestive capacities of the neutrophils.     

Diagnostic suspension for detection of the infective agent of tularemia

The matrix for obtaining silica-based diagnosticum was selected, its activation with surfactant was optimized and its immobilization with tularemia immunoglobulins was carried out. In the glass suspension agglutination test (SAT) the sensitivity of the diagnosticum was 3.125 x 10(6) to 6.25 x 10(6) microbial cells per ml; the duration of SAT, including the evaluation of its results, was 1-5 minutes.     

Suppressing action of splenic cells on macrophage phagocytic activity]

The culture media withdrawn from 18-hour cultures of live spleen cells suppressed the phagocytic activity of peritoneal macrophages in mice. The level of suppression, as estimated for an equal number of spleen cells, varied in individual animals, which seemed to be connected with the level of normal infection in the animals. In the process of development of Ehrlich's carcinoma in mice suppressors were produced in the spleen in an increased amount, but only in connection with the total increase in the number of spleen cells, and not due to the selective accumulation of suppressor cells.