Mechanisms of Antibacterial Action of Bacitracin

Abstract

SUMMARY: At minimal bacteriostatic concentrations, bacitracin had four distinct actions on Staphylococcus aureus: (a) prevention of growth; (b) induction of lysis; (c) suppression of induced enzyme synthesis; (d) stimulation of the reduction of 2,3,5-triphenyltetrazolium chloride. In contrast, penicillin and cycloserine had activities (a) and (b) but neither (c) nor (d), and chloramphenicol had activities (a) and (c) but neither (b) nor (d). With bacitracin, properties (a) and (b) but neither (c) nor (d) were enhanced by Zn2+; other metal ions were inactive. Sequential inactivation of bacitracin by autoclaving revealed that the bacteriostatic property was quite labile whereas the other three activities were more heat resistant. Thus, although several distinct mechanisms have been demonstrated whereby bacitracin can injure bacterial cells, the present data do not indicate which of these, if any, is associated with the primary biochemical lesion that results in suppression of growth.