This is something that as always puzzled me and no doubt someone will point me in the right direction. Q.If antibiotics destroy all bacteria ie. good and bad.Why are the birds droppings to our eyes good ? Q. ,, ,, ,, ,, ,, ,, ,, ,, ,, . Why do we use different antibiotics for different ailments if the above is correct ? Or do all antibiotics kill the good bacteria and not all the bad ?