Penicillin
Penicillin is a group of common antibiotics, used to treat bacterial infections. It was one of the first antibiotics to be discovered, and worked well against staphylococci and streptococci. Many strains of bacteria are now resistant. Chemists keep changing part of its structure in the effort to keep it working against the bacteria. Penicillin is sometimes used to treat syphilis, tonsillitis, meningitis, and pneumonia as well as other diseases.