Concept 1:Antimicrobial spectrum Antimicrobial spectrum: the species of microorganisms that a drug can inhibit or kill. For example, penicillin: Gram-positive bacteria Leptospira（钩端螺旋体) Actinomycetes(放线菌)Concept 1: Antimicrobial spectrum Antimicrobial spectrum: the species of microorganisms that a drug can inhibit or kill. For example, penicillin:  Gram-positive bacteria  Leptospira（钩端螺旋体）  Actinomycetes（放线菌）