Microbial Resistance to Penicillin as Related to Penicillinase or Penicillin Acylase Activity

Abstract

Summary1. The penicillin moiety, 6-aminopenicillanic acid, has antibacterial activity but is considerably less active than penicillin. 2. Resistance to penicillin in one group of bacteria could be explained logically by presence of penicillinase activity, i.e., conversion of penicillin to the inactive penicilloic acid. 3. Resistance to penicillin in a second group of bacteria could be explained logically by presence of penicillin acylase activity, i.e., conversion of penicillin to the relatively inactive 6-aminopenicillanic acid. 4. In a third group of bacteria resistant to penicillin, neither penicillinase nor penicillin acylase activity could be detected. Still another metabolic mechanism other than penicillinase or penicillin acylase activity must be present in selected bacteria.