agar seeded with a chloramphenicol-resistant , penicillinase-negative staphylococcus aureus was used for a cylinder-plate assay of appropriately diluted fluid to determine the activity of either benzylpenicillin or cephalothin after either beta-lactamase inactivation of the former or ultraviolet light inactivation of the latter .
C0030841
penicillinase
C0597979
beta-lactamase