Antibacterial activity from Siamese crocodile (Crocodylus siamensis) serum

Antibacterial agents were purified from Siamese crocodile serum by anion exchange, gel filtration and reversed phase HPLC. Six antibacterial agents designed as Hp14, Hp15, Hp17, Hp31, Hp36 and Hp51 were purified and proved to carry activity against Salmonella typhi, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Vibrio chorelae. The mass analysis of MALDI-TOF for antibacterial agent of Hp14, Hp15 and Hp51 revealed that they are small molecule with a molecular mass less than 1 kDa. The scanning electron microscopy demonstrated that these agents targeted the bacterial membrane and they act like as antimicrobial peptides. The antibacterial agent in the serum may represent the first line of an immune system in a freshwater crocodile.