In Vitro Antibacterial and Antifungal Activity of an <i>Arthrospira platensis</i> (Syn.: <i>Spirulina platensis</i>) Extract

Objective: To assess the antibacterial and antifungal activity in vitro of a patented Spirulina extract on sensitive and multidrug-resistant bacteria, yeasts, and filamentous fungi commonly causing skin infections. Methods: The antimicrobial activity was tested using the drop dilution assay on the Gram-positive bacteria Staphylococcus aureus (wildtype), a methicillin resistant S. aureus, S. epidermidis, S. haemolyticus, Streptococcus pyogenes, the Gram-negative multidrug resistant Pseudomonas aeruginosa, the yeasts Candida albicans and C. tropicalis, and the dermatophytes Trichophyton rubrum and Microsporum gypseum. Results: A concentration of 4 g of Spirulina extract per 100 mL of Mueller Hinton agar completely inhibited the growth of all tested bacteria and yeasts, and suppressed dermatophytes growth by 5 log 10 units. Conclusion: The Spirulina extract tested could be used as an effective natural, broad-spectrum antimicrobial agent, with potential applications in the therapy of bacterial and fungal infectious diseases.