Antibacterial activity of an acidic phospholipase A2 (NN-XIb-PLA2) from the venom of Naja naja (Indian cobra)

The resistance of bacteria against the use of conventional antibiotics has become a serious threat to public health and considering the associated side effect with antibiotics; new strategies to find and develop new molecules with novel modes of action has received grate attention in recent years. In this study, when the antibacterial potential of an acidic protein-NN-XIb-PLA2 (Naja naja venom phospholipase A2 fraction-XIb) of Naja naja venom was evaluated, it showed significant bactericidal action against the human pathogenic strains tested. It inhibited more effectively the gram positive bacteria like Staphylococcus aureus and Bacillus subtilis, when compared to gram negative bacteria like Escherichia coli, Vibrio cholerae, Klebsiell pneumoniae and Salmonella paratyphi. It inhibited the bacterial growth, with a MIC values ranging from 17 to 20 µg/ml. It was interesting to observe that NN-XIb-PLA2 showed comparable antibacterial activity to the used standards antibiotics. It was found that their was a strong correlation between PLA2 activities, hemolytic and antibacterial activity. Furthermore, it is found that in the presence of p-bromophenacyl bromide (p-BPB), there is a significant decrease in enzymatic activity and associated antibacterial activities, suggesting that a strong association exists between catalytic activity and antimicrobial effects, which thereby destabilize the membrane bilayer. These studies encourage further in dept study on molecular mechanisms of bactericidal properties of NN-XIb-PLA2 and thereby help in development of this protein into a possible therapeutic lead molecule for treating bacterial infections.