Marine fungi as a source of antibacterial, antifungal and antibiofilm agents

Introduction: Marine fungi are an underexplored reservoir of bioactive secondary metabolites with significant potential for the development of new therapeutic agents to combat infectious diseases and antimicrobial resistance.

Broad objectives: In this work, the antimicrobial properties of ten marine fungal strains Trichoderma afroharzianum (HP58), Penicillium citrinum (HP26), Talaromyces austrocalifornicus (HPα8), Penicillium rubens (HP10), Tamaricicola sp. (PN38), Phaeosphaeriaceae sp. (PN33), Clonostachys rosea (IG119), Trichoderma sp. (HP31), Talaromyces catalonicus (HP25), and Fusarium clavus (HP54) were investigated using crude extracts obtained from cultures grown on different media.

Methods: Chloroform and butanol extracts from cultures grown on malt extract medium (MEA) were evaluated against Gram-positive and Gram-negative bacterial reference strains exhibiting antibiotic resistance, as well as against the yeast Candida albicans. Antimicrobial activity was assessed through determination of the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum fungicidal concentration (MFC) and antibiofilm activity.

Results: The preliminary in vitro results identified strains Penicillium citrinum (HP26), Talaromyces austrocalifornicus (HPα8), Penicillium rubens (HP10)and Clonostachys rosea IG119 as promising producers of antimicrobial secondary metabolites. In particular, Clonostachys rosea IG119 showed an interesting ability to inhibit biofim formation of Staphylococcus aureus ATCC 25923 with a Biofilm Inhibition Concentration 50% (BIC₅₀) of 22 μg/ml.

Conclusions: Optimization of cultivation parameters could support the isolation of bioactive compounds and enable their detailed chemical and pharmacological characterization. Overall, these findings indicate that marine fungi deserve to be considered an excellent source of antimicrobials.