Table 4.

Mechanisms of antimicrobial action of chlorhexidine

Type of microorganismChlorhexidine action
Bacterial sporesNot sporicidal but prevents development of spores; inhibits spore outgrowth but not germination
MycobacteriaMycobacteristatic (mechanism unknown) but not mycobactericidal
Other nonsporulat-ing bacteria  Membrane-active agent, causing protoplast and spheroplast lysis; high concentrations cause precipitation of proteins and nucleic acids
YeastsMembrane-active agent, causing protoplast lysis and intracellular leakage; high concentrations cause intracellular coagulation
VirusesLow activity against many viruses; lipid-enveloped viruses more sensitive than nonenveloped viruses; effect possibly on viral envelope, perhaps the lipid moieties
ProtozoaRecent studies against A. castellaniidemonstrate membrane activity (leakage) toward trophozoites, less toward cysts