In vitro Studies on Bactericidal Activity and Sensitivity Pattern of Isolated Marine Microalgae against Selective Human Bacterial Pathogens

Ten microalgae cultured under controlled condition were tested for their antimicrobial activity against the selective bacterial pathogens in compliance with paper disk method. Five different solvents were used for the extraction. Isochrysis galbana showed overall inhibition of [16.22%] followed by Chlorella marina [14.43%], Nannochloropsis oculata [14.07%], Dunaliella salina [13.91%] and Pavlova lutheri [13.17%]. These five microalgal strains were further investigated to examine concentration dependent microbicidal activity using tube dilution method. Microalgal strains were also investigated with agar-well diffusion method to understand the efficacy of antimicrobial principles against various bacterial pathogens. The findings in this study reveal that optimal activity is maintained by butanol extracts on Gram-positive bacteria; ethanol and petroleum ether extracts on both Gram-positive and Gram-negative bacteria; methanol extracts on Gram-negative organisms. Chloroform extracts, on the other hand did not show any significant antimicrobial activity.