Conditions for the development of isobaric counterdiffusion of inert gases and the criteria of its evaluation]

Investigation of superficial counterdiffusion of nitrogen against helium has been carried out to evaluate a possibility of its progress in divers (107 tests) under pressures equivalent to 32-450 m of sea water when breathing trimix being saturated in heliox at a constant ambient pressure without changing chamber environment. Breathing gas mixture contained 248-800 kPa of nitrogen, while chamber heliox media contained some additions of nitrogen (6-108 kPa). Clinical manifestations of breathing trimix (itching and gas bubble formation) were studied in divers. The development of counterdiffusion depends on the partial pressure of nitrogen not only in the breathing gas mixture but also in the chamber media. The breathing nitrogen level being increased and (or) decreased in the chamber media, the counterdiffusion symptoms grow relative to the number (%) of cases. Minimal critical values of nitrogen partial pressure gradients in the mixture which induce counterdiffusion skin lesions are 260-320 kPa on the average for the nitrogen concentration in the chamber mixture to 30 kPa. Isobaric supersaturation due to inert gases countertransport in body tissues as a result of gas-switching from heliox to trimix is responsible for the syndrome development.     

Active forms of oxygen as a factor regulating surface characteristics of bacterial cells

AIM: Effects of sublethal concentration of active forms of oxygen (hydrogen peroxide and hydroxyl radical) on cell surface properties of Escherichia coil, Staphylococcus aureus, Bacillus subtilis, and Klebsiella pneumoniae were studied. MATERIALS AND METHODS: Hydrophobicity of cell surface measured by transition of cells from water phase to hydrocarbomic phase and by the ability of bacteria to sorb lysozyme and hemoglobin. RESULTS: Treating of bacterial cells with hydroxyl radicals compared with hydrogen peroxide resulted in more marked decrease of bacteria's hydrophobicity and reduction of their ability to sorb on the surface the lysozyme and hemoglobin. Increasing of the number of R-forms in the bacterial population after contact with hydroxyl radicals was revealed. CONCLUSION: Active forms of oxygen generated in biological systems in concentrations which are not lethal for majority of microorganisms can regulate prokaryote and eukaryote interactions by changing their surface characteristics and therefore they are an ecologic factor determining forming and existence of microbial cenoses.     

Screening of plasmids in the bacteria of the genus Bacillus with antilysozyme activity

In the study of the microbiocenosis of the distal section of the patients' large intestine Bacillus strains with antilysozyme activity (ALA) were isolated. In B. cereus strain 26 with pronounced expression of antilysozyme factor the plasmid sized approximately 100 kb was detected. The transformation of the isolated plasmid in cells of B. cereus non-plasmid strain IP5832 the localization of genes encoding ALA and resistance to kanamycin was determined. The production of ALA factor in the recombinant clone of B. cereus strain IP5832 corresponded to the clinical isolate of B. cereus 26. The replicon of the detected plasmid could be used for the determination of the coding sequence of the antilysozyme sign of bacilli. Genetic determinants of antilysozyme factors and kanamycin resistance may be used for the construction of vector systems of cloning in bacilli.     

Biological properties of salmonellae and local immunity in Salmonella infection

The comparative study of the biological properties of S. enteritidis and S. typhimuruim, isolated from patients and convalescent carriers, was carried out. Factors inactivating the components of the local immunity of the intestine (lysozyme, complement, lactoferrin, IgG, IgM and IgA) were detected in the causative agents of Salmonella infections. The spread and expression degree of properties of a causative agent were serovar-depended: high penetration characteristics and the expression of anti-lactoferrin and anti-immunoglobulin activity were characteristic of S. typhimurium. S. enteritidis strains isolated from patients with carrier state formed in the convalescence period were found to have higher persistence level. In co-profiltrates obtained from carriers at the peak of the disease and during convalescence lower levels of IgM, IgG, sIgA, complement and lactoferrin were determined in comparison with those in coprofiltrates obtained from patients in whom no subsequent carrier state was formed. These results indicate that an increase in the persistence of salmonellae, occurring simultaneously with the local immunodeficiency, contributes to the prolonged survival of bacteria in the intestine.     

Bacterial-fungal associations in the intestine under the conditions of colonization by yeast-like fungi of the genus Candida

The composition of the fecal microflora in somatic patients and patients with enteric infections under the conditions of surpluscolonization by yeast-like fungi of the genus Candida was analyzed. The study revealed that the high level of fungal contamination was linked with decreased colonization resistance of the intestine (deficiency in bifidoflora) and with the presence of opportunistic microorganisms: Staphylococcus aureus, hemolytic and lactose-negative Escherichia coli, as well as nonfermenting Gram negative bacteria. The antilysozyme activity of enterobacteria was found to increase in the course of their joint cultivation with fungi of the genus Candida, that may be regarded as one of the mechanisms of the formation and maintenance of pathobiocenosis.     

Microflora of the large intestine in patients with connective tissue dysplasia

The specific features of intestinal aerobic and anaerobic intestinal microflora in children with nondifferentiated connective tissue dysplasia were under study. A high rate of dysbiotic disturbances was noted in patients with connective tissue dysplasia in comparison with healthy persons. Profound quantitative and qualitative changes in the biocenosis of the intestine were detected in patients with the pathology of the gastrointestinal tract as well as that of the locomotor system. Changes in the species composition and the persistence properties of the intestinal microflora may serve as pathogenetic factors in the development of connective tissue dysplasia.     

Antilysozyme activity of anaerobic bacteria from fecal microflora in man

For the first time anaerobic bacteria of the fecal microflora in man have been found be capable of inactivating lysozyme. The presence of this antilysozyme sign has been noted in both Gram-positive anaerobes (Bifidobacterium, Propionibacterium, Eubacterium, Actinomyces israelii) and in Gram-negative anaerobes (Bacteroids, Prevotella melaninogenica). The expression of antilysozyme activity in the anaerobes under study has been determined. The possible biological role of this sign of the indigenous intestinal microflora has been discussed.     

The antilysozyme activity of Mycobacterium tuberculosis L forms

The method for the detection of antilysozyme activity (ALA) in M. tuberculosis L forms was developed. The level of ALA in M. tuberculosis L forms isolated from patients with different clinical forms of the disease varied within 1-5 micrograms. M. tuberculosis L forms with the ALA level > 4 micrograms were isolated from patients with the progressing course of the disease. The method for the prognostication of the course of the tuberculous process in the lungs by the results of the antilysozyme test was proposed.     

Modification of antibiotic resistance in microbial symbiosis

In antibiotic therapy it is necessary to use drugs active against the pathogen in its association with the host normal microflora. The aim of the study was to investigate modification of antibiotic resistance under conditions of the pathogen association with the representatives of the host normal microflora and to develop the microbiological criteria for determining effectiveness of antibacterials. Modification of microbial antibiotic resistance was investigated in 408 associations. Various changes in the antibiotic resistance of the strains were revealed: synergism, antagonism and indifference. On the basis of the results it was concluded that in the choice of the antibiotic active against Staphylococcus aureus and Streptococcus pyogenes the preference should be given to oxacillin, gentamicin and levomycetin, since the resistance of the pathogens to these antibiotics under the association conditions did not increase, which could contribute to their destruction, whereas the resistance of the normoflora increased or did not change, which was important for its retention in the biocenosis. The data on changeability of the antibiotic resistance of the microbial strains under the association conditions made it possible to develop microbiological criteria for determining effectiveness of antibiotics in the treatment of inflammatory diseases of microbial etiology (RF Patent No. 2231554).     

Symbiosis is a biological basis of infection

Symbiosis has been considered as a biological basis of the infectious process. Attention has been paid to the change of paradigm in symbiology and to the appearance of a new term: associative symbiosis. The main structural-functional elements of associative symbiosis have been assessed, and three vectors of the infectious process have been detected: (1) host-normoflora, (2) host-associants, and (3) associants-indigenous microflora (microsymbiocenosis). Functions of microsymbionts determining host colonization resistance and development of disbioses and pathobiocenoses have been considered. Resistance of organism biotopes to microbes is associated with substrates which are overcome by associants with persistent potential. Antagonism and change of persistent potential in both the infectious agent itself and commensal microorganisms are the basis of symbiont interactions. The given material describes the role of intercellular interactions of symbionts at the level of proprokaryotes, proeukaryotes during the infectious pathology.