Population kinetics of the skin flora under the glove following surgical hand disinfection with three propanol-based hand rubs – a prospective, randomized, double-blind trial

Background and Objectives: The new CDC guideline for hand hygiene recommends either to use an antimicrobial soap or an alcohol-based hand rub supplemented with agents conferring persistent activity for surgical hand antisepsis. The most common agent which is thought to offer this latter type of effect is chlorhexidine gluconate. However, although often claimed, this effect has, to the best of our knowledge, never been adequately confirmed in a randomized, double-blind controlled trial. Methods: Following a 3-min surgical hand disinfection with three propanol-based hand rubs, with or without agents believed to confer a persistent effect, and a 1-propanol 60% (v/v) reference, the population kinetics of re-growth of the skin flora under the glove have been studied at post-treatment times of 0, 1, 3 und 6 hrs in a prospective, randomized, double-blind trial with 24 adult volunteers. A slightly adapted version of the standardized European test method EN 12791 has been used in a Greco-Latin square design such that after eight experiments each subject had tested every formulation at the four sampling times making use of the split-hands model. An ANOVA applied to the lg PRE-treatment values did neither indicate any significant differences of the means obtained from left and right hands nor of those from the 8 experiments of the trial. Results: Equivalence testing of the immediate bactericidal effects revealed that the blinded formulations A (1-propanol 60% v/v) and C (2-propanol 45% g/g plus 1-propanol 30% g/g plus mecetronium etilsulfate 0.2% g/g) were clearly equivalent to the reference, R, whereas that of B (2-propanol 70% g/g plus chlorhexidine gluconate 0.5 g/g) was questionable. The observed population kinetics of the skin flora proceeded as a very strong and fast initial reduction of the bacterial release from the fingertips by 2.7 lg with B and 3.5 lg with C. A and R caused intermediate reductions of 3.1 and 3.4 lg respectively, followed by slow re-growth as indicated by decreasing reductions. They did not reach 0, and were even after 6 hrs still significantly (p < 0.01) 0.9 to 1.5 lg below baseline. The slowest regrowth after 1 and 6 hrs was seen with C (∆ to 0 and 3 hrs = 0.1 lg and 0.7 lg, respectively). After 6 hrs, the slowest regrowth was observed with B (∆ to 0 hr = 1.6 lg). Conclusions: Persistent activity of surgical rubs can not be easily shown if they meet the requirement of EN 12791 to exert an immediate effect equivalent to that of the surgical hand rub procedure laid down there as a reference. All preparations containing a non-volatile active agent caused a (non-significant) slower regrowth of resident hand bacteria than the pure 1-propanols. But the potential of some of such chemicals to cause skin irritation and to promote bacterial resistance should also be considered.