Why can crocodile blood kill some bacteria that even drugs can't kill?

Crocodile serum Crocodiles generally live in poor environments. It is reasonable to say that there are a lot of bacteria, which is easy to make crocodiles sick, but for a long time, crocodiles are almost healthy. If the crocodile's skin is scratched a little, and it lives in water for a long time, it is reasonable to say that bacteria should invade the crocodile, but the crocodile is fine. After a few days, the crocodile's wound healed. After inspection, there are no pathogenic bacteria in the crocodile. Scientists did an experiment for this. Experimental scientists extracted crocodile serum from crocodile. They guessed that crocodile blood might have played a role. They wanted to prove whether their guess was correct, so they put crocodile serum and staphylococcus which had been harmful to people for 5 years in a sealed container, and observed it again after a while-a fierce war began ... When the scientists came back, they took out the container and saw that crocodile serum defeated staphylococcus. The obvious circle in the middle of the container is the forbidden growth area of bacteria formed by crocodile serum. As soon as staphylococcus enters that circle, it will be killed by crocodile serum immediately (the little dots outside are staphylococcus). I didn't expect crocodile serum to beat staphylococci at once, which is also a reason why crocodiles have good resistance. If the experiment is successful, the fetal protein extracted from crocodile serum will become the strongest antibiotic in history and even fight AIDS.