Antibiotiki最新文献

Levorene, a polyenic antibiotic, lowered the concentration of amino acids in the cells of Ehrlich carcinoma. The decrease in the intracellular level of the amino acids was due not only to inhibition of their entrance to the cells but also to their increased leaching from the cells. The effect of levorene on the intracellular level of the neutral amino acids was higher than that on the main amino acids which was associated with different sensitivity of the amino acid transport systems to the antibiotic.

A method for selective isolation of gramnegative nonsporulating bacteria from soil substrates was developed. The method consists of plating out the substrates on a glucose-yeast medium with addition of benzylpenicillin and nalidixic acid. The isolation frequency of gramnegative nonsporulating bacteria increased under such conditions from 9-16 (control) to 80-100 per cent. At the same time the isolation frequency of gram-positive bacteria decreased from 88.5 to 9.6 per cent.

The effect of subbacteriostatic concentrations of some antibiotics on variation of the features characterizing the serovar and biovar of the cholera germ was studied on 10 strains of V. cholerae E1 Tor of the Inaba serovar having the typical properties. It was shown that even a single exposure to the subbacteriostatic concentrations of some antibiotics resulted in formations of clones differing from the parental strains by a number of significant features, such as the antigenic structure, phage lysability and enterotoxicity. The new features were inherited in a number of generations on multiplication in culture media and in sensitive animal hosts.

Lysozyme is an important component of the breast milk. In the gastrointestinal tract of infants it performs the function of a local protective factor. The efficacy of the use of milk enriched with lysozyme was studied in feeding of 64 premature infants suffering from concomitant diseases. This clinical and laboratory study was performed as a part of the combined treatment and prophylactic measures. Lysozyme was added to the donor breast milk or to the dry adapted acidophilic mixture "Malyutka" in an amount of 50 mg per 1 liter of the final product. 29 infants were feeded with such milk products for 14-21 days of the observation period. The control group included 12 infants with artificial feeding and 23 infants feeded with the above milk products without addition of lysozyme. In spite of the significant differences in the initial state of the infants, a favourable effect of the feeding with addition of lysozyme was shown. It was comparable to the feeding with the breast milk. Improvement of the general state of the infants and the pathological processes in them, an increase in the body weight, more rapid sanation of the infectious inflammatory foci, normalization of the stool, stabilization of the lysozyme levels in the coprofiltrates and a tendency to normalization of the increased levels of lysozyme in the blood serum were observed. Satisfactory tolerance of the lysozyme enriched milk products was shown.

The optical properties of the DNA complexes with the compounds of bivalent platinum were studied. The compounds differed by the nature of the anionic and neutral ligands and their spatial arrangement about the platinum atom. It was shown that the same as cis-[Pt (NH3)2Cl2] the platinum compounds with the biological activity, i.e. [Pt (en) Cl2], cis-[PtNH3 (Bz) Cl2] and cis-[Pt (NH3)2NO2Cl] induced at low values of r (a ratio of the number of the platinum moles added to the number of the DNA nucleotide moles in the solution) an increase in the amplitude of the positive band in the spectrum of the circular dichroism (CD) of the linear DNA and a marked decrease in the amplitude of the negative band in the spectrum of the CD of the liquid crystalline microphase of DNA formed in the presence of polyethyleneglycol. By the character of the action on the CD spectrum of the linear and condensed DNA [Pt (tetrameen)Cl2] which had no selective antimitotic effect might be referred to the above platinum compounds. Trans-[Pt (NH3)2NO2Cl], [PtNH3PyCl2], cis-[Pt (NH3)2(NO2)2] and [Pt (NH3)3Cl]Cl having no biological activity either induced only a decrease in the amplitude of the positive band in the CD spectrum of the linear DNA or had no effect on the CD spectrum. The effect of these compounds on the CD spectrum of the liquid crystalline microphase of DNA was slightly pronounced or not observed.

The maximum dehydrogenase (oxidation-reduction) activity of the vegetative inoculum of S. aureofaciens is the criterion of its availability for transfer to the fermentation medium. The activity is determined by the rate of the methylen blue reduction and the growth characteristics of the seed culture. A method for estimation of the mycelium amount in the medium containing insoluble solid particles is described. The method is based on the capacity of the tetracycline-producing organism for decoloration of methylen blue.

The effect of membrane active antibiotics, such as gramicidin S, its derivatives and carbonyl-conjugated pentaens on suspended bacterial protoplasts resulted in lysis of the protoplasts accompanied by a marked decrease in the optical density (OD) of the suspensions. However, when the drug concentrations were lower than those inducing the lysis, an increase in the suspension OD by 10-30 per cent as compared to the control values of the OD was often observed. The increase in the protoplast suspension OD was most pronounced with the use of the drugs with a relatively low lytic activity or under the conditions lowering the lytic activity of the antibiotics. Under such conditions no agglutination of the protoplasts was observed. The comparative estimation of the protoplast diameters by the method of Klenin et al. in the control suspensions of M. lysodeikticus protoplasts and in the suspensions with a stable increase in the OD showed that the OD increase was associated with swelling of the protoplasts: an increase in the suspension OD by approximately 30 per cent corresponded to an increase in the protoplast diameter by approximately 15 per cent. The observed increasing of the suspension OD must be due to the fact that the membrane active antibiotics induced a decrease in the osmotic stability of the protoplasts not sufficient for their lysis.

An agar diffusion method for determination of antibiotic sensitivity to streptococci of different serological groups with semiquantitative estimation of the results was developed with the use of the dry nutrient medium of the I. I. Mechnikov Central Research Institute of Vaccines and Sera for isolation of hemocultures and cultivation of streptococci. The addition of blood or serum to this medium is not required. The standard inoculum (2 milliard microbial bodies) is added into the depth of the nutrient agar thus providing the optimal conditions for the growth of the facultative anaerobes. The MICs of the antibiotics and the diameters of the growth inhibition zones of 150 streptococcal strains were compared and an estimation table for interpretation of the data of the agar diffusion test was presented. This simple method provides a sufficient accuracy and satisfactory reproducibility in the clinical tests.

Occurrence of bacteriocinogeneity in 120 strains of 24 species of Pseudomonas was studied. Active strains producing bacteriocine-like substances were detected among P. fluorescens, P. putida, P. taetrolens, P. fragi, P. stutzeri, P. mendocina, P. maltophilia, and P. pseudoalcaligenes. The bacteriocine-like substances produced by them differed by the morphology of the zones of the test microbe growth inhibition, sensitivity to temperature and enzymes, capacity for dialysis through cellophane membranes and antimicrobial spectrum. The majority of them could be synthesized on agarized and liquid media and induced by UV light and mitomycin C. The strains of P. taetrolens, P. fragi, P. putida and P. fluorescens producing the bacteriocine-like substances had broad antimicrobial spectrum and inhibited the growth of many species of Pseudomonas and representatives of other taxonomic groups of microorganisms.