Effects of chlorhexidine diacetate and cetylpyridinium chloride on whole cells and protoplasts of Saccharomyces cerevisiae.

Chlorhexidine diacetate (CHA) and the quaternary ammonium compound, cetylpyridinium chloride (CPC), were fungicidal to Saccharomyces cerevisiae A364A and CHA to its mannoprotein mutant LB6-5D. Both CHA and CPC induced leakage of K+ and pentose material from both strains and both agents induced protoplast lysis as well as interacting with crude cell sap. Differences were observed between CHA and CPC in protoplast lysis and in cell sap interaction. Q25 values for A364A with CHA as test agent were 5.6 and 1.6 (fungicidal activity, depending on method of calculation), 1.46 (cell sap interaction) and 0.77 (leakage of pentoses). A sub-lytic concentration of CHA reduced considerably protoplast regeneration. Although the plasma membrane is an important target site for both agents, interaction with other cellular components also contributes to fungal death.