Antifungal activity of a Saharan strain of Actinomadura sp. ACD1 against toxigenic fungi and other pathogenic microorganisms.

A new strain of actinobacteria, designated ACD1, was isolated from a Saharan soil sample in the Hoggar region (Algeria). Morphological study led to this strain being classified as a member of the Actinomadura genus. Phylogenetic analysis based on the 16S rRNA gene showed that the strain is closely related to Actinomadura sediminis DSM 45500(T) (98.5% sequence similarity). Furthermore, strain ACD1 presented a strong activity against mycotoxigenic and phytopathogenic fungi, including Aspergillus and Fusarium strains, and other pathogenic microorganisms. The kinetics of antimicrobial activity were investigated on ISP-2, Bennett and TSB media. Four solvents (n-hexane, dichloromethane, ethyl acetate and n-butanol) were used for the extraction of the produced antibiotic. The highest antimicrobial activity was obtained using the butanolic extract from the ISP-2 medium after seven days of fermentation culture. The active antibiotic was purified by reverse-phase HPLC using a C18 column. The UV-visible and mass spectra were determined. The minimum inhibitory concentrations (MIC) of this antibiotic were determined against pathogenic microorganisms.

Antimicrobial activity of saquayamycins produced by Streptomyces spp. PAL114 isolated from a Saharan soil.

A new strain of actinomycete designated PAL114, producing antimicrobial compounds, was isolated from a Saharan soil in Ghardaïa, Algeria. Morphological and chemical studies showed that this strain belonged to the genus Streptomyces. Two bioactive compounds, named P41A and P41B, were extracted by dichloromethane from the cell-free supernatant broth of strain PAL114 and were purified by HPLC. Minimum inhibitory concentrations of the pure antibiotics were determined against yeasts, filamentous fungi and bacteria, most of which are pathogenic or toxigenic for human and multiresistant to antibiotics. The strongest activities were observed against Candida albicans M3 and Bacillus subtilis ATCC 6633. The chemical structures of the compounds were determined by spectroscopic analysis of UV-visible and 1H and 13C NMR spectra and spectrometric analysis of mass spectrum. The compounds P41A and P41B were identified as saquayamycins A and C, respectively. These compounds belong to the aquayamycin-group antibiotics, which are known in the literature for their anticancer and antibacterial activities.

[Antimicrobial activity of a Saharan Streptomyces spp. PAL111 strain against various clinical and toxinogenic microorganisms resistant to antibiotics]. / Activité antimicrobienne de Streptomyces sp. PAL111 d'origine saharienne contre divers microorganismes cliniques et toxinogènes résistants aux antibiotiques.

OBJECTIVE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.