Two Proteins from Snake Venom have Potent Antibacterial Effects against Bacillus anthracis and Streptococcus pneumoniae

Background: Antibacterial proteins are widely expressed in snake venoms. Previously, we have isolated two immunodominant proteins with molecular weights of 14 and 65kD from the snake venom of Naja naja oxiana (N. oxiana). It was demonstrated that they had potent inhibitory effects against gram-positive bacteria, S. aureus and B. subtilis but were less effective against gram-negative bacteria, such as E. coli and P. aeruginosa. This study aimed at investigating the potential antibacterial effects of the two proteins against Bacillus anthracis and Streptococcus pneumoniae. Methods: The proteins were identified by SDS-PAGE and western blot analysis, and isolated by gel electrophoresis (Electro-elution). The antibacterial effects were tested against the strains of Bacillus anthracis and Streptococcus pneumoniae, using broth microdilution and disc-diffusion assays. For comparison, the antibacterial effects of standard antibiotics, such as Gentamicin, Ampicillin, Penicillin, Amoxicillin and Ciprofloxacin were also tested on the same B. anthracis and S. pneumoniae batches under identical laboratory conditions. Results: The two proteins showed high immunogenicity and strongly inhibited the growth of gram-positive bacteria, B. anthracis, and to a lesser extent S. pneumoniae. Conclusions: The isolated proteins demonstrated strong antibacterial effects against Gram-positive bacteria, B. anthracis and S. pneumoniae, in addition to their previously known effects against S. aureus and B. subtilis.