[Characteristics of diffusion of polyene antibiotic levorin].

Studies were performed which provided estimation of the impact of some physico-chemical properties of levorin, a polyene antibiotic, and in particular its multicomponent nature and capacity for isomerization on formation of inhibition zones in assay of the antibiotic activity by the agar diffusion method. It was shown that the levorin complex components markedly differed in the biological activity and diffusion capacity. The diffusive properties of the highly active components A2 and A3 were better.

[Kinetics of thermal inactivation of oleandomycin in aqueous and native alkaline solutions].

The process of oleandomycin inactivation in aqueous alkaline solutions with their heating was studied by using the microbiological method of the antibiotic content assay. The initial specific rate of inactivation of crystalline oleandomycin in buffer solutions and oleandomycin in the fermentation broth filtrate was evaluated. It was shown that the inactivation was retarded by the reaction products and the components of the fermentation broth filtrate.

[Study of oleandomycin extraction in a methylene chloride-aqueous medium system].

Influence of pH, temperature and oleandomycin concentration on distribution of the antibiotic in the methylene chloride-aqueous medium system was studied. It was shown that the oleandomycin distribution coefficient did not depend on the antibiotic concentration within the ranges of 2000 to 20,000 micrograms/ml. An equation defining relationship between the oleandomycin distribution coefficient and pH of the aqueous phase is presented.

[Determining the biological activity of levorin by the international standard of candicidin].

Levorin and candicidin represent close mixtures of heptaenic components. Their physicochemical and biological properties were also close. The antibiotics showed similar diffusive properties in their assay by the agar diffusion method.

[Microcomputer-based automation of the microbiological analysis of antibiotic activity].

Laboratory informative computer systems (LICS-10 and LICS-11) for microbiological assay of antibiotics were developed. The systems are based on the ISKRA-1256 computer. As compared to the routine method with the use of the well-known V.

[Growth of test microorganisms used in determining antibiotic activity on synthetic nutrient media].

The growth of gram-negative sporulating bacteria and yeast-like fungi used in a microbilogical assay of antibiotic activity was studied on solid synthetic media of simple composition. Their reproduction with the microbial growth of different density was shown to be possible on media containing available and strictly standardized components, such as salts, glucose and disubstituted sodium phosphate. The cultures tested were not similar by their growth requirements.

[Size of the area of test-culture growth suppression with polyene antibiotic diffusion into the infected gel as a function of time].

The process of inhibition growth zone formation due to diffusion of polyenic antibiotics into inoculated gel was studied. Variability of the zone size with time was traced as a continuation of the mathematical model of zone formation described earlier. Differences in the zone size variability are shown in case the drug inactivation level is so low that it may be neglected and in case the drug inactivation level is considered.

[Mathematical model of zone formation taking into account the inactivation of polyene antibiotics diffusing into an inoculated gel].

The procedure for investigation of the inhibition growth zone formation on diffusion of polyenic antibiotics into inoculated gel is presented. The model of strong inactivation is applicable when the drug inactivation is significant during the period of the zone formation and not only during the period of the 2-fold increasing of the number of the test microbe cells. The experimental study on the passive inactivation of polyenic antibiotics, such as levorin, amphotericin B, mycoheptin and nystatin showed that during the period of the zone formation the first 2 antibiotics were inactivated to such a level that their passive inactivation could be considered strong.

[Mathematical model of the zone formation in polyene antibiotic diffusion in an inoculated gel].

A mathematical model of inhibition growth zone formation on diffusion of polyenic antibiotics in gel is described. Dynamic equations for the zone formation describing the changes in time of the microbial population density (test microbe) in the presence of the diffusing antibiotics, as well as equations for diffusion of the antibiotics with an account of their inactivation were developed. Extreme cases of no inactivation of the drug by the test microbe are discussed.

[Effect of the nutrient medium components on the formation of growth inhibition zones of the test microbe in determining the biological activity of mycoheptin].

The effect of the nutrient medium components on the diffusion properties of mycoheptin and the growth of Candida utilis as the test-microbe was studied. It was found that the content of various amounts of sodium and potassium chlorides, disubstituted sodium phosphate, glucose, yeast extract, peptone, agar-agar and the value of pH in the medium had a significant effect on the size of the inhibition growth zones of the test-culture, clearance of their margin and the angle of the dose-response curve. The nutrient medium composition considered to be optimal for determination of the mychoheptin activity is proposed.

[Possible use of a single test culture in determining the biological activity of polyene antibiotics].

A possibility using a common test-culture in estimation of biological activity of levorin, amphotericin B, mycoheptin and nistatin was studied. It was found that C. guillier mondii, strain 40, may be used as a common test-culture.

[Differential spectrophotometric method of analysing levorin in the culture broth and in the mycelium].

It was shown on model experiments that the microbiological method was not applicable for determination of levorin content in industrial intermediate products containing in addition levoristatin, since the presence of the latter made higher the results of the microbiological assay. Because of this till to the present date the quantitative content of levorin in the industrial intermediate products was determined photometrically using alcohol (pure solvent) as the reference solution. Still, this method also made higher the results of the assay, especially when the content of levorin was determined in the fermentation broth.

[Effect of the cultivation conditions of Candida species yeast-like fungi on their sensitivity to levorin].

The effect of levorin on yeast-like fungi under (different) cultivation conditions was studied. It was shown that the medium composition and incubation temperature affected the results of determination of the test-culture sensitivity to levorin. There was correlation between the time of the population lag-phase and the critical time of the zone formation and these values depended on the temperature of the test-microbe vegetation.

[Use of paper discs in determining the biological activity of mycoheptin by the agar diffusion method].

Diffusion of mycoheptin from the discs into agar was studied. A procedure providing practical use of the discs for quantitative estimation of mycoheptin activity was developed. A possibility of using the discs in the assay of solutions containing significant amounts of an organic solvent was shown.