Antimicrobial spectra and activities of antibiotic substances from <i>Streptomyces</i> species against sensitive and resistant microorganisms

Abstract

Antimicrobial substances were produced from several Streptomyces species isolated from the soil. The antimicrobial spectra of the antibiotic substances assayed by agar-diffusion technique demonstrated broad-spectrum antimicrobial activity against Staphylococcus aureus, coagulase-negative Staphylococcus aureus, (CONSA), methicillin – resistant Staphylococcus aureus, (MRSA), Bacillus subtilis, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimarium, Shigella dysentariae, Vibrio cholerae, Proteus mirabilis, Klebsiella pneumoniae; while only few of the bioactive substances exhibited antifungal activity against Candida albicans, Aspergillus niger, Trichophyton mentagrophytes, Microsporium gypseum and Epidermophyton floccosum. The minimum inhibitory concentration (MIC) of the bioactive agents assayed by macrobroth-dilution technique were lower against the Gram-positive than the Gram- negative bacteria and fungi, compared with the control drugs (chloramphenicol and ketoconazole), and were significantly (P < 0.05) lower against CONSA, MRSA, Salmonella typhimarium and Shigella dysentariae, compared with the control drugs. Equally, the minimum biocidal concentration (MBC) and establishment of mode of action of the bioactive agents assayed by macrobroth-dilution technique, indicated bactericidal activity, for all the antibiotic substances, while some of the antifungal bioactive agents from the Streptomyces isolates indicated either fungistatic or fungicidal activities.

Keyword: Antimicrobial, Sensitivity Spectra, Streptomyces Antibiotic Substances, soil.