Antiseptic-induced changes in the cell surface of a chlorhexidine-sensitive and a chlorhexidine-resistant strain of Providencia stuartii.

The effects of chlorhexidine diacetate and benzalkonium chloride on the cell surface of a chlorhexidine-sensitive (Pv 2) and a chlorhexidine-resistant (Pv 67) strain of Providencia stuartii are described. Low concentrations of chlorhexidine diacetate (10 mg/l and upwards) increased the hydrophobicity of Pv 2, whilst having little effect on Pv 67. Both strains were resistant to benzalkonium chloride but a concentration as low as 2 mg/l induced a significant increase in hydrophobicity in Pv 2, with 25-50 mg/l needed to induce a similar type of increase in Pv 67. The possible nature of the resistance is discussed.