ampicillin vs. penicillin

a broad-spectrum semisynthetic penicillin, C 16 H 19 N 3 O 4 S, effective against certain susceptible Gram-positive and Gram-negative bacteria.

any of several antibiotics of low toxicity, produced naturally by molds of the genus Penicillium and also semisynthetically, having a bactericidal action on many susceptible Gram-positive or Gram-negative cocci and bacilli, some also being effective against certain spirochetes.