Objectives: Chlorhexidine gluconate (CHG) possesses substantial persistent antimicrobial activity due to its residue on the skin. Despite the availability of many formulations containing CHG, data supporting this notion are scarce. We compared the residual antimicrobial activity of three major types of CHG-containing formulations: 0.5w/v% CHG with 76.9-81.4v/v% ethanol (ethanol formulation), 0.5w/v% CHG aqueous solution (aqueous formulation), and 4w/v% CHG scrub detergent (scrub formulation).
Methods: The residual antimicrobial activities of test formulations were assessed on the forearms of healthy subjects. Circular test sites were set on the left and right forearms. One of the three test formulations was applied to the left forearm. The right forearm was the control. Twenty minutes after application of test formulation, Serratia marcescens was inoculated to all the test sites. Five minutes after inoculation, bacterial samples were collected using cup scrub technique, and were then diluted and spread on the trypticase soy agar plates. Colony forming units of each plate were counted after being cultured for 24 hours, and Log10 reduction (RF) was calculated.
Results: Mean RF was 4.53 for the test sites treated with ethanol formulation (n=6), 3.81 for the test sites treated with aqueous formulation (n=6), and 1.32 for the test sites treated with scrub formulation (n=6). Mean RF following ethanol formulation treatment was significantly greater than that of aqueous formulation and also that of scrub formulation.
Conclusion: Thus, the residual antimicrobial activity differed by the type of CHG-containing formulation, and combining CHG with alcohol may prolong the residual antimicrobial activity.