[Effect of oleandomycin on the growth of the producer Streptomyces antibioticus itself and on its antibiotic synthesis]. / Vliianie oleandomitsina na rost sobstvennogo produtsenta Streptomyces antibioticus i antibiotikoobrazovanie.

It was shown that addition of oleandomycin to the fermentation broth during development of Str. antibioticus inhibited the mycelium growth within the first 2 days and lowered the level of its further biosynthesis. The inhibitory effect depended on concentration of the added antibiotic and medium composition. An excess of glucose increased the inhibitory effect of oleandomycin. The antibiotic influenced both synthesis of the oleandomycin macrolide ring and methylation of the molecule.

[Circular dichroism study of amphotericin B interaction with the sterols of Candida albicans strains sensitive and resistant to polyene antibiotics]. / Izuchenie vzaimodeistviia amfoteritsina B so sterinami chuvstvitel'nogo i rezistentnogo k polienovym antibitokam shtammov Candida albicans metodom krugovogo dikhroizma.

The method of circular dichroism (CD) was used to study interaction of amphotericin B with liposomes of egg lecithin containing sterols isolated from sensitive and resistant strains of Candida albicans. Analysis of the CD spectra showed that the antibiotic spectral parameters in the dispersion of liposomes modified with sterols underlie definite changes. In case of sterol isolated from the sensitive culture they were evident from an increase in the relative intensity of the negative extremes at 415, 390 and 370 nm. The contours of the CD spectrum in the region of 350 nm significantly changed proportionally to the antibiotic concentration and during incubation. The CD spectra of amphotericin B in the dispersions of the lecithin liposomes containing sterols isolated from the resistant strain of C. albicans were characterized by an increase in the relative intensity of the negative extremes at 415, 390 and 370 nm. These changes also took place during incubation. Still, the frequency character of the spectrum did not practically change. Only the intensity in the spectral region tested somewhat changed proportionally within an hour. The results indicate that the character of antibiotic interaction with liposomes containing sterols of the sensitive and resistant cultures significantly differs. This means that the changes in the membrane sterol composition (ergosterol and delta 7.22-ergostadien-3 beta-ol were the main sterols of the sensitive and resistant cultures respectively) have a marked effect on the character of the antibiotic interaction with them.

[Characteristics of a strain of C. albicans resistant to polyene antibiotics]. / Kharakteristika shtamma C. albicans, ustoichivogo k polienovym antibiotikam.

It was found that a resistant strain R2 of C. albicans obtained as a result of passages on media containing increasing concentrations of amphotericin B differed from the initial strain by its lower pathogenicity. Treatment of the infection caused by the resistant strain on modeling of candidiasis in mice was not successful. The decrease in the average life span of the mice infected with the resistant strain R2 and treated with amphotericin B was lower than that in the control animals and such indices of the disease as the levels of the kidney dissemination and the cell vegetation even increased under the effect of amphotericin B. The results of the study suggest that the resistant strain R2 of C. albicans depend on amphotericin B in the host. The data obtained emphasize the necessity of determinining the antibiotic sensitivity of C. albicans strains isolated from patients.

[Sterol affinity of Candida albicans cells resistant to polyene antibiotics]. / O srodstve sterinov rezistentnykh kletok Candida albicans k polienovym antibiotikam.

The affinity levels of sterols in the sensitive and resistant cultures of C. albicans for polyenic antibiotics were studied comparatively. The affinity level was determined by liberation of potassium under the effect of the antibiotic participating in interaction with the sterol. The protective effect of the sterol suspended in solution and included into the composition of the liposomes from egg lecithin was studied. It was found that the sterols of the resistant cultures of C. albicans had the same (or even somewhat higher) affinity to amphotericin B as those from the sensitive cultures. The data indicate that resistance of the strains studied is not based on the loss of the sterol capacity for binding polyenic antibiotics.

[Composition and certain properties of Candida albicans cells with a low level of resistance to polyene antibiotics]. / Sostav i nekotorye svoistva kletok Candida albicans s nizkim urovnem rezistentnosti k polienovym antibiotikam.

The lipid and protein composition of Candida albicans, strain R3, with a low resistance to polyene antibiotics does not differ much from that of the parent, susceptible culture. Nevertheless, the rate of potassium release from the cells and the incorporation rate of 14C-amino acids in the cells of C. albicans, strain R3, under the action of amphotericin B are lower as compared to the susceptible culture; therefore, the resistance of C. albicans, strain R3, must be due to a decrease in the degress of its disordered selective permeability. Sterols isolated from the cells in both strains were found to be capable of binding to polyenes at a high rate in solution. However, sterols from the strain R3 with a low resistance to polyenes, when incorporated into a synthetic lipid membrane, increase its permeability slower than sterols from the susceptible strain, which suggests that sterols from the low-resistant strain R3 are possibility involved in the phenotypic manifestation of resistance.

[Change in the composition of Candida albicans cells during development of resistance to polyene antibiotics]. / Izmenenie sostava kletok Candida albicans pri vozniknovenii rezistentnosti k polienovym antibiotikam

The composition of lipid and protein components of the membrane structures was studied in the strains of Candida albicans susceptible and resistant to polyene antibiotics. The content of sterols was lower and the content of free fatty acids was higher in the cells of resistant strains cf. susceptible strains. The composition of sterols was also different in the resistant strains: analysis of absorption spectra of sterol extracts in heptane in UV revealed complete absence of ergosterol, the main component of the susceptible strain, and appearance of a heterogenous peak at 215--240 nm.