if a drug works well for a R.I. it doesn't mean that every time that snake gets a R.I. that it will work well. what's making the snake sick has to be sensitive to the drug that's being used in treating that snake. this is why a vet will do a culture to see what the bacteria is most sensitive to. snakes usually get gram - (neg) bacteria. we usually get gram + (pos) and thats why the drugs we use are not used on snakes. also gram - are nasty, they are usually more complex than gram + and require very strong drugs.