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N S Smirnova

Publications and source records attributed to N S Smirnova.

At least 19 recordsLinked to original sources
PubMed2003

[Comparison of nitrate reductase and automatic BACTEC MGIT 960 AST techniques for determining the drug sensitivity of mycobacteria tuberculosis].

The accelerated nitrate reductase method (NRM) developed at the Central Research Institute of Tuberculosis versus the automatic assay of drug sensitivity by means of a BACTEC 960 bacteriological analyzer was assessed. NRM was carried out, by using the Lówenstein-Jensen medium for 10 days. It is based on the detection of alive Mycobacteria tuberculosis, by recording their enzymatic activity. The study showed a good agreement of the results obtained by NRM with those obtained on a BACTEC 960 analyzer. Agreements were found for 52 isolates in 47 (90.4%) cases, the results disagreed in the testing of 5 (9.6%) cultures. The results of NRM were identical to those for 21 of the 22 cultures sensitive on a BACTEC 960 device; the coincidence was 95.5%. The sensitivity of NRM ranged from 88.2% (for rifampicin) to 96.3% (for isoniazid) and the specificity did from 96% (for isoniazid) to 100% (for streptomycin, rifampicin, and ethambutol). The positive prognostic value of NRM was 100% (for streptomycin, rifampicin, and ethambutol) and 96.3% (for isoniazid). The negative prognostic value of NRM ranged from 94.6 to 96.8% for individual drugs. The efficiency of NRM (a ratio of the number of correct results to the total number of results) was greater than 0.96, which suggests that this method and the BACTEC MGIT 960 AST technique may be regarded as rather comparable. The testing of NRM versus the automatic BACTEC MGIT 960 AST technique has indicated that the former may be successfully used to determine the sensitivity of Mycobacteria to the critical concentrations of first-line antituberculous agents.

Antitubercular Agents↗
PubMed2001

[Automated methods of culture determination of M. tuberculosis in liquid media].

A hundred and seventy respiratory samples from patients with different forms of tuberculosis were used to test the efficiency of the automatic liquid culture systems BACTEC MGIT 960 and MB/BacT with inoculation into the standard dense media. All these media provided 47 M. tuberculous isolates, of them 41 (87.2%), 38 (80.9%), and 76.6% on the BACTER 960, MB/BacT, and dense media, respectively. The average time of detection of mycobacterial growth by means of automatic systems was much shorter and equal to 10.7 days on the BACTEC 960 and 18.7 days on the MB/BacT versus 33.2 days on the standard dense medium. In terms of their sensitivity and detection rate, the automatic systems were superior to the dense media widely used in laboratory practice.

Bacteriological Techniques↗
PubMed1998

[Mechanism of action of lomefloxacin on Mycobacterium tuberculosis].

The peculiarities of the mechanism of the lomefloxacin bactericidal action on Mycobacterium tuberculosis were studied. The electron microscopy of ultrathin sections of the cells of M.tuberculosis H37Rv exposed to 10 micrograms/ml of lomefloxacin for 24 hours revealed severe changes in their ultrastructure: exfoliation of the cell wall from the cytoplasmic membrane, loosening and fragmentation of the cytoplasmic membrane, lowering of the cytoplasm thickness, vacuolization and twisting of the mesosomes. The exposure of the cells to lomefloxacin for 72 hours resulted in their complete destruction: the cells proved to be a mass of unidentifiable fragments. Some destructions such as exfoliation of the intracytoplasmic membrane and the cytoplasm loosening and vacuolization were observed in the tubercle bacilli localized inside the phagosomes of the murine lung macrophages exposed to lomefloxacin. Such destructions were evident of the antibiotic good penetration not only into the macrophages but also through the phagosome walls as well as of the lomefloxacin intracellular bactericidal activity. In the experiments with the culture of the lung tissue from the tuberculosis foci of mice the basic mechanism fo the lomefloxacin action on M.tuberculosis was demonstrated: the lomefloxacin bactericidal effect was realized through the pathway of mechanism A of the antimicrobial action of fluoroquinolones.

Animals↗
PubMed1992

Persistence of Rickettsia prowazekii in cotton rat macrophage cultures.

Rickettsia prowazekii is able to multiply and persist for a long time in cotton rat macrophage culture (29-days observation period). Electron microscopic studies showed that the structure of Rickettsiae remained intact at different intervals post-inoculation (p.i.). In the course of persistence Rickettsiae revealed a reduced capacity to infect chick embryos and guinea pigs, however, the infectious agent could be isolated at all stages of persistence of cultured cells such as fibroblasts of the guinea pig embryo, macrophages of intact cotton rats.

Animals↗
PubMed1992

[The ultrastructure of a new species of Chlamydia--Chlamydia pneumoniae].

The dynamic study of a new Chlamydia species, C. pneumoniae (strain TWAR, isolate TW-480), inoculated into the monolayer culture of cells L-929 was made 24, 48, 72 and 96 hours after inoculation. When compared with C. trachomatis and C. psittaci, C. pneumoniae were found to stand between these two species with respect to the morphology of their intracytoplasmic microcolonies (inclusions): they were round, almost bubble-like, but more densely packed with chlamydiae, surrounded by an undulate membrane, preserving its integrity until the late stages of their development cycle. In cells L-929 C. pneumoniae had a typical development cycle accompanied by the formation of vegetative and spore-like cells, reticular and elementary bodies, as well as intermediate cells, though this process was slower than in C. trachomatis and C. psittaci. Besides normal elementary bodies, many altered ones were formed in the process of the development of C. pneumoniae in cells L-929. Most of these alterations were similar to the process of bacterial L-transformation and could be regarded as the manifestation of chlamydial pathology related to the adaptation to new host cells.

Animals↗
PubMed1991

Ultrastructure of Chlamydia pneumoniae in cell culture.

The electron microscopic appearance of Chlamydia pneumoniae elementary bodies with pear-shaped, loose outer membrane has been suggested as one criterion of its classification as a new chlamydial species. The study of the original strain TW 183 in LCL 929 and HL cells and a low-passage isolate of Kajaani-6 isolate in HL cells revealed spherical compact elementary bodies common to other chlamydia.

Chlamydophila pneumoniae↗
PubMed1991

[The ultrastructure of the interaction of Rickettsia sibirica and R. slovaca with the cells of ixodid ticks].

The ultrastructural aspects of the interaction of R. sibirica and R. slovaca with cells of mites of the species Dermacentor reticulatus, D. marginatus and Ixodes ricinus after their parenteral infection, as well as in the organs of D. marginatus infected naturally in the environment, have been studied. Both rickettsial species have similar morphology in different organs of the vector. These rickettsiae not only multiply, their populations are also partly destroyed in phagolysosomes. The natural mixed infection of R. sibirica and orbivirus in cells of D. reticulatus is described. As shown in this study, both associates pass through the complete ontogenetic cycle of development on the level of the host body and also on the level of an individual cell.

Animals↗
PubMed1990

[The surface antigens of Rickettsia prowazekii studied with monoclonal antibodies].

R. prowazekii antigens have been tested with the use of monoclonal antibodies (McAb) to different epitopes of the microorganism. As revealed in these tests, McAb B4/4 and A-3/D, active against species-specific thermolabile antigen, interact with protein having a molecular weight of 90-120 KD. McAb C5/2, active against thermostable group antigen common with that of Rickettsia typhi, interact with LPS-like antigen having a molecular weight of 30 KD. Ultrastructural immunochemical studies have revealed that both R. prowazekii antigens are located on surface structures of rickettsiae, such as the microcapsule and cell wall.

Antibodies, Monoclonal↗
PubMed1989

Methods for purification of Rickettsia prowazekii separated from the host tissue: a step-by-step comparison.

Two methods for purification of Rickettsia prowazekii strains E, E Vir, and Breinl grown in chick embryo yolk sacs are described. These methods combine either differential centrifugation or sucrose mix, centrifugation through sucrose cushion, 10 mmol/l MgCl2 treatment, filtration through a glass filter AP-20 and 2 cycles of verografin discontinuous density gradient centrifugation. The purification procedure including sucrose mix allowed to recover about 38-42% biologically active rickettsiae, a yield which was by 10% higher than that obtained by the method beginning at differential centrifugation. The rickettsiae free of host cell components preserved their infectious activity. The obtained biomass was suitable for immunological and biological characterization of Rickettsia prowazekii and for isolation of its total DNA.

Animals↗
PubMed1988

[The sensitivity of a number of cell cultures to different strains of Rickettsia prowazekii].

The sensitivity of some cell cultures to different R. prowazekii strains (strain E with low pathogenicity, virulent strain Breinl, strains ERifRI and EVir) has been studied with a view to the selection of an adequate culture for growing these strains and the study of their biological properties. Experiments on titration in cells have revealed that 6- to 7-day primary and secondary irradiated quail fibroblasts and human amnion cells FL show the maximum sensitivity to all strains under study, comparable to that of chick embryos. The sensitivity of 6- to 7-day primary and secondary irradiated chick fibroblasts is faintly pronounced, and 24-hour chick and quail fibroblasts are still less sensitive. Cells FL have shown high sensitivity to strain E and mutant ERifRI in prolonged subculturing for 140 and 63 days (the term of observation) respectively after a single inoculation.

Animals↗
PubMed1987

Electron microscopic analysis of in vitro interaction of Rickettsia prowazekii with guinea pig macrophages. I. Macrophages from nonimmune animals.

Monolayer cultures of peritoneal macrophages of intact guinea pigs were infected with Rickettsia prowazekii (strain Breinl) and examined by electron microscopy after 30 min, 4 and 24 hr post-infection (p.i.). Three parallel processes developed in infected macrophages: reproduction of rickettsiae in macrophage cytoplasm, destruction in phagolysosomes and production of spheroplast-like forms. Reproduction of rickettsiae yielded 2 cell types: those with dense and with light cytoplasm; they were located side by side in the microcolony and seemed to have a common capsule-like coat. Relatively small spheroplast-like forms of about 1 micron in size were regularly detected. Addition of immune serum to macrophages increased the number of rickettsiae, both of rod-shaped as well as of spheroplast-like ones located within phagosomes, but elicited no increase in the number of digested pathogen cells.

Animals↗
PubMed1987

Electron microscopic analysis of in vitro interaction of Rickettsia prowazekii with guinea pig macrophages. II. Macrophages from immune animals.

Alike to macrophages from intact animals, reproduction, destruction and formation of spheroplast-like forms were observed in macrophages from immune guinea pigs 2 months post-infection (p.i.) with the virulent Breinl strain of Rickettsia prowazekii. Unlike to the former, immune macrophages revealed phagolysosomes which were larger in size and contained more rickettsiae showing morphologic signs of destruction. Spheroplast-like forms occurred more often and were more numerous than in intact animals. Structures morphologically similar to L-forms of gram-negative bacteria and that of chlamydiae were also detected. After adding immune serum, more intact rickettsiae and spheroplasts were found in phagosomes as well as more phagolysosomes contained rickettsiae and spheroplasts with morphologic signs of destruction. It is suggested that clearance of immune macrophages from rickettsiae is mediated by at least two processes: on one hand by destruction of rod-shaped rickettsiae within phagolysosomes and, on the other hand, by formation and subsequent destruction of spheroplast-like forms within vacuoles, which probably also function as phagolysosomes.

Animals↗