Evaluation of the Antifungal Activity of Metabolites Produced by Soil Actinomycetes on the Candida Species Isolated from Candidemia.

BACKGROUND

Actinomycetes are a well-known group of bacteria that produce critical metabolites. This study aimed to identify the bioactive actinomycetes from soil samples that exhibit antifungal activity against Candida species isolated from the blood of patients with candidemia.

MATERIALS AND

METHODS

Twelve soil samples from southwestern Iran were cultured on starch casein agar to isolate actinomycetes. The antifungal activity of the isolates was screened using a modified overlay agar technique. Five Candida species isolated from candidemia patients (Candida albicans, C.glabrata, C.lusitania, C. tropicalis, and C. parapsilosis) were tested using well diffusion agar assays. Seven actinomycetes with the strongest anticandidal activity were identified by 16S rDNA gene sequencing and compared to gene sequences in the NCBI database using the BLAST program.

RESULTS

Of the 52 actinomycete isolates, seven demonstrated significant antifungal potency against Candida isolates. Sequencing identified four actinomycete genera: Crossiella, Streptomyces, Saccharothrix, and Amycolatopsis. Crossiella cryophila showed the strongest inhibition against Candida parapsilosis, with a halo diameter of 42.5 ± 13 mm. Streptomyces exhibited a weaker inhibitory effect across all tested Candida species, with its highest activity against C. parapsilosis (a halo diameter of 35 ± 17.3 mm, P ≤ 0.05). Amycolatopsis alba displayed the weakest antifungal effect against C. lusitaniae compared to other Candida species (P ≤ 0.05).

CONCLUSIONS

This study reports the presence of novel actinomycetes in Iranian soil that can produce anti-Candida compounds. These isolates hold promise for potential therapeutic applications in treating patients with candidemia.