الفهرس 
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Abstract
The escalating use of antimicrobial medical agents and long-term treatment approaches has led to an increased prevalence of microbial species that are resistant to the most common antimicrobial drugs. Accordingly, it is necessary to continue screening for new bioactive metabolites.
The main objective of this study was designed to isolate actinobacteria possessing antifungal hygiene activity against some dermatophytes, Epidermophyton floccosum AUMC6185, Trichophyton rubrum AUMC5467, Microsporum canis AUMC13575 and Candida albicans and optimize various growth and nutritional conditions for antifungal metabolite production then purify and characterize of the bioactive substance.
Therefore, sixty-four actinobacterial isolates were isolated from different localities in Egypt and screened for their antifungal activity against the three tested dermatophytes and C. albicans. Only two actinobacterial isolates, ML15 and MH7 were found to have antifungal efficiency against the tested fungi. Study of cultural, morphological, physiological, biochemical characteristics as well as chemical components of the cell wall strongly suggested that the two isolates belonged to the Streptomyces spp. Analysis of the 16S rRNA gene of the two actinobacterial isolates ML15 and MH7 showed that ML15 was in high similarity (99.81%) with
Streptomyces rochei, while MH7 was in high similarity (99%) with Streptomyces canescens.
Also, some important hydrolytic enzymes of the two identified actinobacterial isolates were evaluated. For increasing the antifungal metabolite(s) by the two strains, nutritional and environmental conditions have been optimized for growth.
Diethyl ether was the best solvent for extraction of the bioactive agent(s) obtained from S. rochei ML15. Purification of the crude extract was carried out by column chromatography technique, out of ten fractions only one fraction F7 (obtained from gradient CHCl3/CH3OH, 90:10) appeared activity against the tested fungi.
MIC of the purified antifungal compound against the tested fungi was found to be in the range of 15.62 - 31.2 μg/ml, MFC was ranged between 31.25 – 125 μg/ml as compared with fluconazole (7.8 -15.62 μg/ml) and (15.62 - 62.5 μg/ml) respectively.
Effect of the pure antifungal compound on the tested fungi showed absence of macroconidia and thinning of mycelium in all tested dermatophytes. Whereas on C. albicans absence of budding, sharp reduction of yeast cell numbers and size, distortion of the ovoid shape of the cells, changes in the space between the cell wall and plasma membrane, and a reduction of the cytoplasmic content were observed. Finally, the structure elucidation of the antifungal compound was established based on UV, FTIR, HNMR,
EL-MS and elemental analysis and found that it has a molecular formula of C32H54O4.