Testing of the World Health Organization recommended formulations in their application as hygienic hand rubs and proposals for increased efficacy
Application time and alcohol content influence the efficacy of the alcohol-based WHO formulations for hand disinfectants
In this study the bactericidal activity of WHO I (ethanol 80 % v/v) and WHO II (isopropanol 75 % v/v) in hygienic hand disinfection was investigated. The prospective, randomised, crossover in-vivo laboratory study was conducted at the Institute for Hygiene and Applied Immunology, Medical University Vienna, Austria with 20 test persons. Evaluation of the preparations’ efficacy was carried out in accordance with EN 1500. As the WHO Guidelines do not define exact application times, the study examined the application of both 1 x 3 ml/30 seconds and 2 x 3 ml/2 x 30 seconds. The bactericidal efficacy on hands artificially contaminated with Escherichia coli K12 was compared with the efficacy of the reference procedure (isopropanol 60 % v/v, 2 × 3 ml). Additionally, for the exposure time of 30 seconds, it was tested which effect increased alcohol concentrations (weight instead of volume percent) have. With the short application (30 seconds), the reduction of microbial contamination yielded by either preparation recommended by WHO was significantly inferior (WHO I: 3.59 ± 0.89; WHO II: 3.57 ± 0.82) to the reference procedure (4.29 ± 1.00; 4.11 ± 1.10). Within 30 seconds, test products with increased alcohol content produced log10 reductions similar to the reference procedure. Application of 2 x 3 ml for 60 seconds also yielded reduction factors that meet the EN 1500 efficacy criteria.