General Description Chemical structure: ß-lactam Application Penicillin G is a narrow spectrum antibiotic derived from Streptococcus pneumonia e. It is the drug of choice for groups A, B, C and G streptococci, nonenterococcal group D streptococci, viridians group streptococci, and non-penicillinase producing staphylococcus. The potassium salt has been used to study murosomes of staphylococci and the penicillin-induced lysis of Streptococcus mutans. Other Notes Keep container tightly closed in a dry and well-ventilated place. Keep in a dry place.