Interaction of chlorhexidine with cytoplasmic membranes of Streptococcus mutans GS-5.

Cytoplasmic membranes of Streptococcus mutans GS-5 were extracted by incubating cells with 1% sodium lauroyl sarcosinate for 20 min at room temperature. The profiles of membrane proteins were determined by SDS-PAGE and isoelectric focusing. The effect of chlorhexidine digluconate on cell membranes was studied after treating the extracted proteins for 30 min with the drug at final concentrations of 0.05 and 0.2%. Chlorhexidine caused selective reduction in the intensity of the membrane proteins. Five densely staining bands with molecular weights of 24.2, 19.6, 18.1, 17.6 and 16.4 kD were obviously diminished. Isoelectric focusing indicated that chlorhexidine preferably precipitated acidic cytoplasmic proteins (pI 4.0-4.92). Our results are consistent with the hypothesis that the mode of action of this drug is mainly attributed to its hydrophilic property. Chlorhexidine, being cationic, may interact with bacteria by attraction to negative-charge membrane components.