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Background. Streptomycetes were and remain a source of new antimicrobial compounds of various nature. A new wave of interest in such research is associated with the possibilities of applied genomics to reveal the hidden biosynthetic potential of streptomycetes, and therefore the discovery of new practically valuable antimicrobial products. The problem of antibiotic resistance of pathogens can be solved by creating compositions of active substances of different nature to overcome the protective mechanisms of pathogens. Objective. The purpose of the work was to establish and evaluate the antimicrobial and cytotoxic characteristics of the new antibiotic streptofungin, synthesized by Streptomyces albus 2435 (CMIM-S-668) and its mutant strains 2435/М, UN44, 4S, US101, AE6, 105, 80/5. Methods. To establish the characteristics of streptofungin, the antagonistic activity of selected S. albus producer strains was determined (by the radial streak method), the minimum inhibitory concentration of the antibiotic (by the serial dilution method), and cytotoxicity was determined by the MTT test with resazurin. Results. The activity of the antibiotic streptofungin against Candida fungi (C. albicans, C. utilis) is shown. Minimum inhibitory concentrations of streptofungin were determined for C. albicans ATCC 10231 (10 μg/ml), B. subtilis ATCC 6633 (200 μg/ml) and P. aeruginosa ATCC 9027 (500 μg/ml). According to the resazurin test, streptofungin does not show a cytotoxic effect in a wide range of concentrations from 2.5 to 500 μg/ml, and therefore can be considered potentially permissible for humans and animals in the studied concentrations. Conclusions. The antagonistic activity of mutant strains of S. albus culture is due to the action of a complex of antimicrobial products that have a different antimicrobial spectrum and mechanism of action. The obtained results give reasons to consider streptofungin as a promising pharmaceutical substance with antifungal action, as well as to consider the possibility of its combination with the bacteriolytic enzyme complex of the same culture for the development of an antimicrobial agent with a wide spectrum of action.

Background. The fight against the spread of infectious diseases creates the problem of resistance to pathogens and the most resistant of them – the propagators of nosocomial infections – are formed in hospitals because of a number of reasons. The solution of the problem lies in different areas, but the search of new effective means for the treatment of such diseases remains relevant right today. The shortest way to do this is to find the "pain points" of the pathogens themselves, i.e. the factors of their pathogenicity and resistance to which the action of novel antiseptics should be directed. Objective. We aimed to analyse and evaluate the main factors of pathogenicity and resistance of pathogens of nosocomial infections to determine modern approaches to the development of novel antimicrobials. Methods. Search and systematization of new scientific data and results concerning pathogenic factors of microbial pathogens that can be used as targets for the action of drugs. Results. Over the last 10–20 years, due to the development of new research methods in biology, it has become possible to clarify the features and additional conditions for the detection of pathogenic factors of nosocomial infections. Additional mechanisms of manifestation of resistance, adhesiveness, invasiveness, transmission of signs, secretion of toxins by pathogens are shownthat determines the general increase of their resistance to the action of currently used means. The general idea of ​​creating antiseptics that will not increase the resistance of pathogens can now be implemented by using substances with multidirectional or indirect mechanisms of action that minimally affect the metabolism of the cell and significantly reduce its resistance and pathogenicity. Conclusions. Factors of pathogenicity of propagators of nosocomial infections and mechanisms of their implementation can be considered as the main targets for the action of novel antiseptics that will inhibit the spread of pathogens without increasing their resistance. The promising substances for such drugs, among other things, are bacteriophages and their modifications, enzybiotics, immunobiotics, autoinducer inhibitors, quorum sensing-system inhibitors, b-lactamase inhibitors and others. Some of these substances in combination with the new generation of antibiotics significantly enhance their effectiveness and together they are able to overcome the resistance of even multidrug-resistant pathogens.

Background. Scientific bases for the development of microbial-derived polycomponent preparations for plant growing, which show a wide specificity of biological action. Objective. The aim of the paper is an establishment of the biological activity of S. albus UN44 experimental preparations for cucumber plant bioregulation processes for further substantiation of optimization directions of ready-made forms and application methods. Methods. The experimental preparations were produced by cultivating the S. albus UN44 producer, in subsequently separating biomass and (in one variant) heat sterilization of supernatant. The cucumber seeds of the variety Konkurent were treated with solutions of the preparations and the growth stimulation, metabolic activity of plants, and the state of stress were determined. Results. It is determined that Biopreparat-1 stimulates the growth of the root and stem of the cucumber after seed treatment with a solution at a concentration of 15–22 units/ml (or 1–1.5 %). It is shown, based on the data obtained, that the biological activity of culture preparations can be due to the presence of hormones of the auxin class that were not previously identified among its metabolites. For the first time, the ability of S. albus UN44 biopreparations to influence the proline content in cucumber plants, and therefore their stress resistance, is shown. Conclusions. The results of the research are the basis for studying new biologically active products of S. albus UN44 and optimization of the ready-made forms of preparations, namely sterile liquid form and dry complex preparation, as well as preparations of certain metabolites with target highly specific activity. The ability of experimental preparations to influence the plant stress resistance requires additional study and makes it possible to create means for correcting the effects on plants of various negative factors.