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S M Navashin

Publications and source records attributed to S M Navashin.

At least 91 records · Page 5Linked to original sources
PubMed1985

[A dynamic system for the in vitro study of the kinetics of the antimicrobial effect of antibiotics in pharmacokinetic changes in their concentration].

The present approaches to in vitro investigation of the kinetics of the antibiotic antimicrobial effect are based on its recording at one or another constant concentration of the drugs. The regularities revealed under such conditions do not usually reflect the peculiar effect of the drugs in vivo, since with the use of the routine schemes of dosing the drug levels in the body fluids always vary. For investigation of the kinetics of the antimicrobial effect of antibiotics at their varying levels, a universal dynamic system providing in vitro simulation of the pharmacokinetic profiles of the drugs in blood and tissues was developed. The system is based on the controlled dilution of the medium containing an antibiotic and microbial cells. the dynamic system allows simulation of any kinetic profile of the drugs with regard to the constants of the linear pharmacokinetic N-compartmental model. The trial of the dynamic system as applied to the antimicrobial effect of sisomicin on strain A 20 363 of E. coli revealed significant differences in the effect of the drug, when its bioexponential pharmacokinetic profile was simulated in a one-compartmental model with exponential absorption and a constant concentration of the antibiotic. The check determinations of the antibiotic concentration in the main flask of the system showed that the system provided high accuracy simulation of the required antibiotic levels.

Dose-Response Relationship, Drug↗
PubMed1985

[A spectroturbidimetric method of rapid evaluation of microbial sensitivity to antibiotics].

A rapid spectroturbidimetric method for estimation of the microbial sensitivity to antibiotics is described. It provides quantitative determination of significant structural parameters of bacterial suspensions, such as the average values of the cell radius or the radius of the cell conglomerates r lambda, their numerical concentration N and the concentration of the intact cells by the dry weight C. The relative changing of the biomass during the culture growth is a reliable index of the microbial sensitivity to the antibiotic effect. The changing of the biomass is determined by direct estimation of C, but not by the suspension turbidity measured at one light wavelength. The collection strains E. coli M-17 and S. aureus 209P were used. The spectra of the optical density were measured with the use of the apparatus made in the USSR. It was noted that the resolving capacity and realization rate of the spectroturbidimetric method wee higher than those of the routine agar diffusion method. The spectroturbidimetric method provides determination of the culture sensitivity to several antibiotics for 4 hours.

Anti-Bacterial Agents↗
PubMed1985

[Isolation of protein hydrolysates by using immobilized bacterial peptide hydrolases].

Preparation of medical protein hydrolysates with the use of complete hydrolysis of proteins by bacterial enzyme complexes, such as protosubtilin G10x and bacterial peptidase immobilized on aminosilylated alumina was shown to be possible. The activity, thermostability and substrate specificity of the heterogeneous biocatalysts were studied. The integral kinetics of the hydrolysis of sodium caseinate and peptides included in partial acid and enzymatic casein hydrolyzates and blood was investigated. The engineering approaches to mathematical simulation of the bioproteolysis kinetics and the results of their use in processing of the experimental data are discussed.

Aluminum Oxide↗
PubMed1985

[Use of beta-lactamase from Bacillus licheniformis 749/C for solid-phase immunoenzyme analysis].

beta-Lactamase from Bacillus licheniformis 749/c was used as a marker for ELISA. Conjugates of the beta-lactamase with the capsule antigen of the plague causative agent and with the monoclonal antibodies to it were prepared by glutaric aldehyde "linking". The conjugates preserved high immunospecific and beta-lactamase activity. High sensitivity of the modification of ELISA allowed detecting up to 8 ng/ml of the capsule antigen of the plague causative agent. The enzymatic activity of the beta-lactamase was determined microiodometrically which provided visual recording of the results of ELISA.

Antibodies, Monoclonal↗
PubMed1985

[Use of antibioticograms for individual programs of antibacterial therapy].

The increasing role of antibiotic-resistant microorganisms in etiology of bacterial infections and the increased number of the antibiotics used for the treatment of patients with purulent infections require a rational approach to the choice of the optimal drug. Antibiotic sensitivity of the causative agents of bacterial infections is considered at present as one of the main indices determining the efficacy of antibacterial therapy. Determination of antibiotic sensitivity by the disk diffusion method with quantitative and semi-quantitative interpretation of the results provides information for choosing the most effective drug and calculating its optimal dose in control therapy. Equations for calculating the MICs antibiotics by the inhibition growth zones and the drug levels in blood and urine attained with the use of different doses and administration routes are presented.

Anti-Bacterial Agents↗
PubMed1984

[DNA cloning in actinomycetes: the creation of vector systems].

A new vector type was constructed on the basis of SLP 1.2 plasmid and the Kanr determinant of S. rimosus P3. It was shown that the determinant was capable of amplifying in the chromosomes of S. rimosus during its improvement for increasing the level of resistance to kanamycin. Cloning of the Kanr determinant was performed on the Pst I-A fragment of the SLP 1.2 plasmid in S. lividans 66. The Kanr determinant was expressed in the resulting hybrid plasmids, e. g. pSU 3, thus providing resistance of S. lividans to 20 micrograms/ml of kanamycin. As a result of repeated passages variants capable of growing in the presence of 50 000 micrograms/ml of the antibiotic were selected. The electrophoretic analysis of the total DNA fragments obtained after exposure to different endonucleases showed that they were identical to the respective fragments of the hybrid pSU 3 plasmid and amounted to approximately 40 per cent of the total DNA. The presence of the unique sites for the Bam HI, ClaI and SacI restriction endonucleases on the pSU 3 plasmid in an insignificant area and the relative stability (30-100 per cent) of the amplified variants allowed using it for cloning and amplification of DNA in Streptomyces. Plasmids were identified with the genetic and physical methods in 13 strains of the blue systematic group among the 72 strains studied. A multicopy plasmid with a molecular weight of 5.6 MD designated as pSB 24.1 was identified in the family of the plasmids of S. cyanogenus. The deletion and insertion variants of the pSB 24.1 plasmid were obtained. The comparative study of the properties of these plasmids revealed the areas insignificant for replication and maintenance of the pSB 24.1 plasmid and the area determining the Ltz+-phenotype. It was suggested that formation of the deletion and insertion variants of the pSB 24.1 plasmid was provided by the site specific recombination mechanisms. The presence of the unique sites for a number of the restriction endonucleases located in the insignificant area, the presence of the selective marker and the high transformation frequency allowed one to consider the multicopy pSB 24.1 plasmid an acceptable vector for cloning of DNA in Streptomyces.

Chromosome Mapping↗
PubMed1984

[Restriction analysis of the plasmid and chromosomal DNA of the strain Streptomyces fradiae--a producer of neomycin].

Plasmid DNA with a molecular weight of 53-55 Md was isolated from Streptomyces fradiae strain 676 producing neomycin on centrifugation of the DNA preparation at the density gradient of cesium chloride-ethidium bromide. The extrachromosomal DNA had 6 recognition sites for Bgl II, more than 13 recognition sites for Bam HI, more than 14 recognition sites for Kpn I, more than 18 recognition sites for Pst I, more than 20 recognition sites for Sac I, more than 21 recognition sites for Pvu II and no recognition sites for Eco RI, Eco RV, Hind III and Sla I.

Chemical Phenomena↗
PubMed1984

[Substrate specificity of the beta-lactamases found in a number of clinical strains of gram-negative bacteria].

The substrate profiles of beta-lactamases defected in 46 clinical polyresistant strains of gram-negative bacteria were determined. By the substrate profile and sensitivity to inhibitors (dicloxacillin and p-CMB) beta-lactamases were considered to belong to classes I, II, III, IV and V of the Richmond classification. The molecular weights of the enzymes were measured. Enterobacter aerogenes 6803, Enterobacter aerogenes 11030 and Klebsiella pneumoniae 970 produced simultaneously two beta-lactamases belonging to different classes. beta-Lactamases of classes I and III were detected in the cells of Enterobacter aerogenes 6803. The cells of Enterobacter aerogenes 11030 contained beta-lactamases of classes V and III and the cells of Klebsiella pneumonia 970 beta-lactamases of classes II and III. Therefore, in all the cases one of beta-lactamases belonged to the class III enzyme close to TEM beta-lactamases by its substrate profile, molecular weight and sensitivity to the inhibitors. Cephalexin and dicloxacillin were most frequently stable to the effect of the above beta-lactamases. The enzymes from 26 strains did not hydrolyse or hydrolysed slightly cephalexin and the enzymes from 19 strains did not hydrolyse of hydrolysed slightly dicloxacillin.

Anti-Bacterial Agents↗
PubMed1984

[Isolation and properties of beta-lactamase of the cephalosporinase type from cells of Enterobacter aerogenes 6803].

beta-Lastamase with the molecular weight of 32500 was isolated from the cells of clinical strain 6803 of Enterobacter aerogenes and purified. By the substrate profile determined microiodometrically beta-lactamase was classified as belonging to the cephalosporinase type. The activity of the electrophoretically homogenous enzyme was equal to 430 microM a minute per mg protein with respect to benzylpenicillin. The Km for benzylpenicillin, dicloxacillin, cephaloridin and cephalothin was 6.5410(-5), 3 X 10(-4), 2.1 X 10(-5) and 5.7 X 10(-5) M, respectively. The isoelectric point of the enzyme equal to 5.45 was estimated with the method of preparative isoelectrofocusing. The presence of the serine residue or residues was shown with the use of selective reagents applied to the functionally important groups. With the method of circular dichroism the ratio of alpha- and beta-structures in the enzyme molecule was determined, the slow hydrolysis of cephazolin was demonstrated and the values of Km and Kcat for this process were estimated.

Cephalosporinase↗
PubMed1984

[Various aspects of the chemotherapy of bacterial infections].

The principles of rational antibiotic therapy in modern conditions are considered. The mechanism of action of the main antibiotics widely used for the treatment of infectious diseases and indications to the use of combined antibiotic therapy are analyzed. Good prospects for the use of immunomodulators and agents inhibiting microbial cell enzymes in a number of pathological conditions are shown.

Anti-Bacterial Agents↗