Antagonistic effects of fungal and actinomycete strains on selected pathogens [Articol]

Abstract

Background: Filamentous fungi and actinobacteria are valuable biotechnological resources that play a key role in the pharmaceutical industry as sources of antibiotics effective against pathogenic bacteria and fungi. Identifying microbial strains active against opportunistic pathogens, including Candida albicans, Escherichia coli, and Salmonella, is essential for developing new therapeutic strategies. The aim of this study was to select new strains with antimicrobial potential against some opportunistic pathogens and pathogens. Materials and methods: A screening of 24 Penicillium and Trichoderma strains of fungi and 7 strains of Streptomyces actinobacteria was performed. The strains of fungi and actinobacteria were tested against the opportunistic pathogenic fungi Aspergillus fumigatus, Fusarium solani, Fusarium oxysporum, the pathogen Candida albicans and the pathogenic bacteria Escherichia coli, Salmonella and Enterococcus spp. The tests were performed by the disk-diffusion method adopted by Egorov [1]. Results: The study results showed that, out of 24 fungal strains evaluated for activity against the opportunistic pathogens A. fumigatus, F. oxysporum, and F. solani, as well as the pathogen C. albicans, 2 strains were highlighted: Penicillium sp. 12 and Penicillium sp. 14. The inhibition zones against the opportunistic pathogens varied within the range of 22–32 mm, whereas against C. albicans, the inhibition zones were insignificant, measuring 14–15 mm. Against the pathogenic bacteria E. coli, Salmonella, and Enterococcus spp. (E. faecium and E. faecalis), none of the studied fungal strains showed antagonistic activity. Among the 7 actinobacterial strains studied for their antifungal properties against the opportunistic fungi F. solani, F. oxysporum, and A. fumigatus, 2 strains were identified— Streptomyces gougerotii CNMN-Ac-14 and Streptomyces fradiae CNMN-Ac-11—with inhibition zones of 23–28 mm. The strain S. fradiae CNMN-Ac-11 also showed antagonism against C. albicans, with insignificant inhibition zones of 14–15 mm. None of the actinobacterial strains tested against the pathogens E. coli, Salmonella, and Enterococcus spp. (E. faecium and E. faecalis) showed antagonistic activity. Conclusions: According to the obtained results, we can conclude that the strains: Penicillium sp. 12, Pencillium sp. 14, S. gougerotii CNMN-Ac-14 and S. fradiae CNMN-Ac-11 are promising for combating opportunistic pathogenic fungi such as A. fumigatus, F. solani, F. oxysporum, but cannot combat pathogenic bacteria.