Before penicillin?

Penicillin was discovered (by accident) in 1928 by Alexander Fleming.

Work done with it in 1942 by Howard Florey and Ernest Chain led to its use by allied troops starting in 1943.

The three above named men received the Nobel Prize in medicine in...

1945.

My question is what did mankind use to fight diseases before penicillin?

Before that were Sulfonamide drugs (sulfa drugs) from the early 30s. It was the first drug that could effectively treat a range of bacterial infections inside the body.

Before that were herbal remedies which were hit or miss in their efficacy. Since nothing worked very well 100 years ago, anyone could claim success with leeches, blood-letting, witchcraft, voodoo, herbs, or laying on of the hands.