Activité antifongique d'une souche d' Actinomadura d'origine saharienne sur divers champignons pathogènes et toxinogènes

Exploring the antimicrobial and antioxidant properties of Lentzea flaviverrucosa strain E25-2 isolated from Moroccan forest soil

The alarming rise in antimicrobial resistance (AMR) has created a significant public health challenge, necessitating the discovery of new therapeutic agents to combat infectious diseases and oxidative stress-related disorders. The Lentzea flaviverrucosa strain E25-2, isolated from Moroccan forest soil, represents a potential avenue for such research. This study aimed to identify the isolate E25-2, obtained from soil in a cold Moroccan ecosystem, and further investigate its antimicrobial and antioxidant activities. Phylogenetic analysis based on 16S rRNA gene sequences revealed the strain's classification within the Lentzea genus, with a sequence closely resembling that of Lentzea flaviverrucosa AS4.0578 (96.10% similarity). Antimicrobial activity in solid media showed moderate to strong activity against Staphylococcus aureus ATCC 25923, Bacillus cereus strain ATCC 14579, Escherichia coli strain ATCC 25922, Candida albicans strain ATCC 60193 and 4 phytopathogenic fungi. In addition, ethyl acetate extract of this isolate demonstrated potent antimicrobial activity against 7 clinically multi-drug resistant bacteria. Furthermore, it demonstrated antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, as well as a significant increase in ferric reducing antioxidant power. A significant positive correlation was observed between antioxidant activities and total content of phenolic compounds (p < 0.0001), along with flavonoids (p < 0.0001). Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of amines, hydroxyl groups, pyridopyrazinone rings, esters and pyrrolopyrazines. The Lentzea genus could offer promising prospects in the fight against antibiotic resistance and in the prevention against oxidative stress related diseases.

Antimicrobial potential of Streptomyces coeruleofuscus SCJ isolated from microbiologically unexplored garden soil in Northwest Morocco

Research on microorganisms in various biotopes is required to identify new, natural potent molecules. These molecules are essential to control the development of multi-drug resistance (MDR). In the present study, a Streptomyces sp., namely SCJ, was isolated from a soil sample collected from a Moroccan garden. SCJ isolate was identified on the basis of a polyphasic approach, which included cultural, micro-morphological, biochemical, and physiological characteristics. The sequence of the 16S rRNA gene of the SCJ strain showed 99.78% similarity to strains of Streptomyces coeruleofuscus YR-T (KY753282.1). The preliminary screening indicated that the SCJ isolate exhibited activity against Candida albicans ATCC 60,193, Escherichia coli ATCC 25,922, Staphylococcus aureus CECT 976, Staphylococcus aureus ATCC 25,923, Bacillus cereus ATCC 14,579, Pseudomonas aeruginosa ATCC 27,853, as well as various other clinical MDR bacteria and five phytopathogenic fungi. The ethyl acetate extract of the isolated strain demonstrated highly significant (p < 0.05) antimicrobial activity against multi-resistant bacteria and phytopathogenic fungi. The absorption spectral analysis of the ethyl acetate extract of the SCJ isolate obtained showed no absorption peaks characteristic of polyene molecules. Moreover, no hemolytic activity against erythrocytes was observed in this extract. GC-MS analysis of the ethyl acetate extract of the SCJ isolate revealed the presence of 9 volatile compounds including 3,5-Dimethylpyrazole, and pyrrolizidine derivatives (Pyrrolo[1,2-a]pyrazine 1,4-dione, hexahydro-3-(2-methylpropyl)), which could potentially explain the antimicrobial activity demonstrated in this study.

Optimization of antifungal production by an alkaliphilic and halotolerant actinomycete, Streptomyces sp. SY-BS5, using response surface methodology

OBJECTIVE

Optimization of medium components and physicochemical parameters for antifungal production by an alkaliphilic and salt-tolerant actinomycete designated Streptomyces sp. SY-BS5; isolated from an arid region in south of Algeria.

MATERIALS AND METHODS

The strain showed broad-spectrum activity against pathogenic and toxinogenic fungi. Identification of the actinomycete strain was realized on the basis of 16S rRNA gene sequencing. Antifungal production was optimized following one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches. The most suitable medium for growth and antifungal production was found using one-factor-at-a-time methodology. The individual and interaction effects of three nutritional variables, carbon source (glucose), nitrogen source (yeast extract) and sodium chloride (NaCl) were optimized by Box-Behnken design. Finally, culture conditions for the antifungal production, pH and temperature were studied and determined.

RESULTS

Analysis of the 16S rRNA gene sequence (1454 nucleotides) assigned this strain to Streptomyces genus with 99% similarity with Streptomyces cyaneofuscatus JCM4364(T), the most closely related. The results of the optimization study show that concentrations 3.476g/L of glucose, 3.876g/L of yeast extract and 41.140g/L of NaCl are responsible for the enhancement of antifungal production by Streptomyces sp. SY-BS5. The preferable culture conditions for antifungal production were pH 10, temperature 30°C for 09 days.

CONCLUSION

This study proved that RSM is usual and powerful tool for the optimization of antifungal production from actinomycetes.

A non-polyenic antifungal produced by a Streptomyces yatensis strain isolated from Mellah Lake in El Kala, North-East of Algeria

OBJECTIVE

This study aimed at describing one actinomycete strain E65 that was isolated from the water of Mellah Lake in El Kala, North-East of Algeria that produces a non-polyenic antifungal.

MATERIALS AND METHODS

Actinomycetes were isolated from Mellah Lake water and screened for antimicrobial activity. Antimicrobial assays were performed on ISP2 agar. The taxonomic position of the strain E65 was determined regarding phenotypic and 16S DNA sequences features. Time course of antifungal metabolites production was evaluated against Candida albicans on ISP2, ISP1 and GYEA broth. The active antifungal compound was extracted using dichloromethane and revealed by a thin layer of chromatography, chemical reagents, UV-visible and infrared spectroscopy.

RESULTS

A total of 104 actinomycetes were isolated and screened for antimicrobial activity; 21 strains were active against Staphylococcus aureus, Escherichia coli and Candida albicans. The strain E65 showed a high in vitro activity against S. aureus and C. albicans and a good antifungal activity against a clinical C. albicans strain resistant to 5-fluorocytosine. Its 16S rRNA sequence shared 99% similarity with the Streptomyces yatensis type strain within the Streptomyces violaceusniger subclade of the Streptomyces hygroscopicus clade. It produced a non-polyenic antifungal, the IR spectrum of the antifungal extract corresponded to none of the antimicrobials compounds known to be produced by actinomycete of the S. hygroscopicus clade.

CONCLUSION

The wetlands of El Kala, Algeria are a potential source of bioactive actinomycete that deserves to be explored and exploited. The Streptomyces yatensis E65 strain isolated from Mellah Lake brackish water produces a remarkable antifungal compound which original non-polyenic structure warrants further characterization.

Actinomycetes from solitary wasp mud nest and swallow bird mud nest: isolation and screening for their antibacterial activity

The aim of this study was to isolate and screen actinomycetes from solitary wasp and swallow bird mud nests for antimicrobial activity. The actinomycetes were isolated from soil of nests of solitary wasp and swallow bird, and identified on the basis of morphological characteristics and molecular biological methods. A total of 109 actinomycetal isolates were obtained from 12 soil samples (6 from each habitat) using two media. The highest number of actinomycetes were recovered on Humic acid vitamin agar media (65.13%, n = 71) as compared to actinomycetes isolation agar media (34.86%, n = 38). The antimicrobial activity of actinomycetes isolates was determined using the agar plug method. Among 109 isolates, 51 isolates (46.78%) showed antibacterial activity by agar plug assay. The morphological and molecular characteristics confirmed that the most of active isolates in both sample belonged to the genus Streptomyces, the other potential genera like Streptosporangium, Actinomadura, Saccharopolyspora, Thermoactinomycetes and Nocardia were also recovered, but in a low frequency. The isolates designated as 8(1), BN-6, MN 2(6), MN 2(7) and MN 9(V) showed most promising activity against various drug resistant bacterial pathogens. It seems that the promising isolates from these unusual/unexplored habitats may prove to be an important step in development of drug for treating multi-drug resistant bacterial pathogens.