Traditional antibacterial activity of freshwater microalga Spirulina platensis to aquatic pathogens.

The crude ethanol, methanol and aqueous extracts of Spirulina ( Spirulina platensis) have been investigated for antibacterial activity using disc diffusion assays against various strains of fish and shellfish pathogens e.g. Pseudomonas putida ( ATCC 49128; PP1, PP2), Pseudomonas aeruginosa ( ATCC 35032; PA1, PA2), Pseudomonas fluorescens ( PF1, PF2), Aeromonas hydrophila ( ATCC 49140; AH1, AH2, AH3, AH4), Vibrio alginolyticus ( VA), Vibrio anguillarum ( VAN), Vibrio fluvialis ( VF), Vibrio parahaemolyticus ( VP), Vibrio harveyi ( VH), Vibrio fisheri ( VFS), Edwardsiella tarda and animal isolates of Escherichia coli ( O115, O1, O156, O164, O111 and O109). The minimum inhibitory concentrations ( MIC) of crude extracts were determined using the tube dilution method. Ethanolic extract showed comparatively higher antibacterial activity (15.66 mm) than that of methanolic and aqueous extract of S. platensis along with their respective MIC values, ranging from 100 to 150 μg mL⁻¹. The aqueous extract had no effective antibacterial activity against the test microorganism. The study suggested that S. platensis may have potential use in aqua feed as an antimicrobial agent of pharmaceutical interest. [ABSTRACT FROM AUTHOR]