Antimicrobial activity of freshwater cyanobacteria isolated from pharmaceutical wastes

Abstract

The present study evaluates the phytochemical screening and antimicrobial activity of two species of cyanobacteria namely, Phormidium chalybeum and Leptolyngbya tenuis isolated from hospital discharge waste waters near Mangalore. They were maintained in BG11 media. In vitro screening of organic solvents (methanol, ethanol, chloroform and petroleum ether) and their aqueous extracts was carried out against seven species of bacteria namely, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Aeromonas hydrophila, Proteus vulgaris, Pseudomonas aeruginosa and Klebsiella pneumoniae. Antimicrobial assay was carried out using disc-diffusion method. All the four organic solvents and aqueous extracts of the species showed activity against tested bacteria. Methanol extract was highly effective against all the bacterial strains (p<0.01) except E. coli followed by ethanolic extract (p<0.05), while ethanolic extract showed significant minimum inhibitory concentration (MIC) values (p<0.01). The study revealed antifungal activity against Aspergillus niger, Aspergillus flavus and Candida albicans while Alternaria alternata was found to be resistant in the ethanol and water extracts, whereas the methanol and chloroform extracts exhibited significant inhibition activity (p<0.01), followed by diethyl ether extract (p<0.05). Methanolic extracts showed significant MIC values (p<0.01) against tested fungi. The occurrence of cyanobacteria in such waters may necessitate the development of certain adaptation strategies and production of antimicrobial compounds.