Activité antimicrobienne de Streptomyces sp. PAL111 d’origine saharienne contre divers microorganismes cliniques et toxinogènes résistants aux antibiotiques

Abstract

Study of the taxonomy and the biological activity of the actinomycete strain PAL111 against several pathogenic and toxigenic microorganisms for humans, and resistant to many antibiotics. The taxonomic study of isolate PAL111 is carried out on the basis of phenotypic and molecular characteristics. The tests against the pathogenic microorganisms are realized on ISP-2 and Bennett media. The kinetics of antibiotic production was investigated on ISP-2 medium. The antibiotic is highlighted by bioautography and chemical revelations, and then purified by chromatography on thick layer of silica gel and Sephadex LH20 column. The minimum inhibitory concentrations (MIC) were determined against pathogenic microorganisms. The phenotypic and molecular studies showed that the isolate PAL111 is closely related to the type strain of Streptomyces ambofaciens. It showed a strong activity against Candida albicans, filamentous fungi, and Gram-positive and Gram-negative bacteria. The optimal antibiotic production was observed at the end of the exponential phase of growth and at the beginning of the decline phase. The bioautography tests showed the presence of an antibiotic with both antibacterial and antifungal activities. This antibiotic is a hydrophilic amino-glycoside compound. The MIC were observed between 2 and 20μg/mL for yeasts, 10 and 50μg/mL for filamentous fungi, 2 and 10μg/mL for Gram-positive bacteria, and 20 and 75μg/mL for Gram-negative bacteria. The strong activity of isolate PAL111 against the pathogenic microorganisms and the polar characteristic of the produced antibiotic could encourage further studies on this bioactive molecule.