Detection of Naganishia albida Yeasts in Dermatological Patients.

The yeasts Cryptococcus albidus (Naganishia albida) usually occur on natural substrates and rarely are the etiological factor of different mycoses. More than a half of mycosis cases described in the literature were reported during the period from 2004 to 2021. In this regard, evaluation of yeast sensitivity to antimycotic drugs is as important as their identification. In the present study, two yeast isolates from the skin of female patients (age 7 and 74 years) with infective dermatitis (ICD-10-CM Code L30.3) were studied. Common identification of the isolates, MALDI-TOF mass spectrometry, and analysis of the nucleotide sequences of the ITS1-5.8S-ITS2 rDNA region showed that they belong to the species N. albida. The sensitivity of the obtained strains to antimycotics of three different chemical groups, namely itraconazole, naftifine, and amphotericin B, determined by microdilution method in a synthetic medium showed the following minimum inhibitory concentrations: 64-128, 16, and 0.125-4 µg/ml, respectively. It was found that the sensitivity of this yeast to pooled human serum was 30-47%, i.e. lower by 1.9-2.9 times than the sensitivity of the collection strains of C. albicans and C. neoformans. This result could be explained by lower prevalence of N. albida in the human population in comparison with these species. However, the sensitivity of N. albida strains to the low-molecular-weight fraction of serum was approximately the same as in C. albicans and C. neoformans, which indicates their high sensitivity to antimicrobial peptides.

Effect of Albumin on Tumor Cells In Vitro.

The study examined the effect of BSA on cultured cells of breast cancer, erythroleukemia, and ovarian carcinoma. BSA cytotoxic activity was examined with light microscopy and spectrophotometry in the concentration range of 6.25 to 50 mg/ml. The high concentrations of BSA disrupted the tumor cells in parallel with formation of vesicular debris. The destruction parameters were similar in diverse types of cells: BSA (50 mg/ml) disrupted 75.5±0.7% breast cancer cells, 75.8±0.2% erythroleukemia cells, and 78.8±0.1% cells of ovarian carcinoma (p≥0.05). The effect of BSA was dose-dependent in each type of cells. The data attest that BSA can disrupt various tumor cells in vitro.

Antimicrobial Effect of Albumin on Bacteria and Yeast Cells.

We studied the effect of albumin (human serum, bovine serum, and ovalbumin) on Candida albicans, Cryptococcus neoformans, E. coli, and Staphylococcus aureus cells. Antimicrobial activity was evaluated by microscopy, inoculation, and spectrophotometry. All three albumins showed antimicrobial activity against all studied cultures and their effect was dose-dependent. At concentrations of serum albumins close to physiological (50 mg/ml), the cells of microorganisms were destroyed with the formation of debris vesicles, while at lower concentrations (10 mg/ml), only cell membrane integrity was impaired. According to spectrophotometry, activity of the human serum albumin in a physiological concentration against the studied microorganisms was close to the activity of native human serum.

Congenital immune defense of the hair.

Studies of two recent decades provided ample data on antibacterial peptides protecting animal and human epithelium of different types; however, no reports about the presence of these compounds in hair keratinocytes appeared up to the present time. Peptides were extracted from specimens of normal intact hair with citric acid solution in 50% ethanol. Antibacterial activity of the resultant extracts was evaluated on Candida albicans test culture by staining and microscopy, by evaluation of growth inhibition zones, and by inoculations. Direct contact with the extract destroyed the greater part of Candida albicans cells up to complete destruction of membranes. Application of the extract to dishes with agar with Candida albicans led in the formation of apparent zones of growth inhibition. The percentage of killed cells increased with prolongation of incubation with the extract. Electrophoresis of hair extract showed bands characteristic of antibacterial peptides RNase, psoriasin, and ß-defensins. Removal of the peptides from the extract by filtration through membrane filter led to loss of its activity. The results indicate that human hair keratinocytes possess congenital antibacterial immunity.

Modified method for evaluation of plasma membrane integrity in eukaryotic cell.

We propose a method for evaluation of the number of viable cells by the content of bromcresol purple dye absorbed by dead cells from the incubation medium. Myramistin was used as a pore-forming agent. The number of live cells in yeast suspension inversely correlated with the percentage of dye absorbed by cells. The method is simple and requires no special equipment. The effect of myramistin on Candida albicans and Malassezia sympodialis cells and on epitheliocytes was evaluated. Two-hour treatment with myramistin in a concentration commonly used in clinical practice (100 mug/ml) decreased the number of viable cells by 2 and 1 order of magnitude, respectively. Epitheliocytes under the same conditions absorbed approximately the same mount of the dye as Candida cells.

[Killer toxins of clinically important yeasts]. / Killernye toksiny klinicheski znachimykh drozhzhei.

The review deals with some theoretical and applied aspects of the capacity of yeasts for synthesizing toxins. Similarly to antibiotic formation in micellar fungi and actinomycetes and the synthesis of bactericins in prokaryotes, yeast cells also have their mechanism of protection from other microorganisms. The substances, essentially of the same nature, synthesized by yeast are known for more than 30 years as mycocins or killer toxins. They are proteins or glycoproteins, active mainly against yeast microorganisms. Mycocins are not active against bacteria and protozoa exhibiting only fungicidal or fungistatic action. The formation of mycocins may be determined by nucleus or plasmid DNA. In this review information on killer toxins produced by clinically important yeasts of the genera Candida, Cryptococcus and Rhodotorula is systematized.