Scientists in Australia’s tropical north are collecting blood from crocodiles in the hope of developing a powerful antimicrobial drugs for humans, after tests showed that the reptile’s immune system kills HIV.The crocodile’s immune system is much more powerful than that of humans, preventing life-threatening infections after savage territorial fights that often leave the animals with gaping wounds and missing limbs."They tear limbs off each other and despite the fact that they live in this environment with all these microbes, they heal up very rapidly and normally almost always without infection,” said U.S. scientist Mark Merchant, who has been taking crocodile blood samples in the Northern Territory.Initial studies of the crocodile immune system in 1998 found that several antibodies in the reptile’s blood killed bacteria resistant to penicillin, such as Staphylococcus aureus, Australian scientist Adam Britton told Reuters on Tuesday. It was also a more powerful killer of HIV than the human immune system.