To study the bacterial population kinetics on gloved hands following hand treatment with 3 optically indistinguishable, alcohol-based surgical hand rubs, with and without supplements to delay bacterial regrowth.
Prospective, randomized, double-blind, balanced quasi-Greco-Latin square design.
Microbiology laboratory of the Medical University Vienna, Austria.
Twenty-four healthy adult volunteers without skin lesions.
Surgical Hand Rubs.
The following hand rubs, all stained blue, were applied to the hands for 3 minutes: 1-propanol 60% vol/vol (A); 2-propanol 70% m/m plus chlorhexidine gluconate 0.5% wt/wt (B); 2-propanol 45% wt/wt plus 1-propanol 30% wt/wt plus mecetronium etilsulfate 0.2% wt/wt (C). As a reference formulation (R), 1-propanol 60% vol/vol, unstained, was applied for the same amount of time.
In 8 once-weekly tests, 24 subjects randomly assigned to use the 4 hand rubs in groups of 6 persons each performed hand hygiene according to the method described in European Norm 12791. Every subject used one preparation at a time, the antimicrobial effect of which was evaluated at 2 sampling times. After week 8, each volunteer had tested every preparation at every preset sampling time. All preparations were tested in parallel.
The mean pretreatment counts of viable bacteria (in colony-forming units per milliliter) in fluid samples were not significantly different between week 1 and week 8, nor between the right and left hands (analysis of variance [ANOVA], P > .1). Immediately after applying the formulation (t0), bactericidal effects of the blinded formulations A and C were equivalent to that of the reference formulation R, whereas the effect of B was questionable. The population kinetics of the flora on the hands proceeded from large and fast initial reductions of the skin flora by 2.7 log units (A), 3.1 log units (B), 3.3 log units (reference formulation), and 3.5 log units (C), to slow regrowth. However, even after 6 hours wearing gloves viable bacterial counts remained significantly (P < .01) below the baseline values (by 0.9 log [reference formulation], 1.1 log [A and B], and 1.5 log [C]). The slowest regrowth 1 and 3 hours after application (∆ from t0, 0.1 log and 0.7 log respectively) was seen with formulation C, and the slowest regrowth after 6 hours was seen with formulation B (∆ from t0, 1.6 log). These differences did, however, not reach statistical significance.
With respect to the rapid and dramatic antibacterial action of suitable alcohols at high concentrations and with appropriate neutralizers, the contribution of supplements to the delay of bacterial regrowth on gloved hands appears rather minor, if a product only exerts an immediate effect equivalent to that of the reference disinfection procedure described in EN 12791.