The efficacy of several new handwashing agents for removing non-transient bacterial flora from hands

Forty subjects participated in a study of four handwashing agents evaluated for their efficacy in removing non-transient bacteria: 70% isopropanol, 0.05% stabilized iodine, 4% chlorhexidine gluconate, and 1% para-chloro-meta-xylenol. Each subject performed a non-medicated handwash to remove transient flora. Afterwards, three consecutive experimental handwashes were performed using a 10-second contact time, and a fourth handwash employed a 1-minute contact time. Quantitative post-handwash cultures were obtained using the sterile bag technique incorporating an effective agent neutralizer. Significant mean log10 reductions were documented for chlorhexidine gluconate, but only after the third (P = .05) and fourth (p = .004) handwash; however, the total log10 reduction was less than 1.0 for any single agent. Subsequently, three evaporative handwash agents, including 70% isopropanol, 0.5% chlorhexidine in 70% isopropanol, and a 60% isopropanol formulation containing evaporative retardants, were tested in 14 subjects. Contact time was prolonged to the point of evaporation prior to culturing. Four consecutive post-handwash cultures were obtained after performing a baseline pre-handwash culture. When compared with the other two evaporative agents, the 60% isopropanol formulation demonstrated significant mean log10 reductions for each handwash (p less than or equal to .03), with a total log10 reduction of 2.9 over all four handwashes (p = .0001). The brief contact time incorporated in our handwashing technique reflects clinical usage patterns. The marked bacterial reduction demonstrated by the 60% isopropanol formulation warrants further study.