Influence of applied volume on efficacy of 3-minute surgical reference disinfection method prEN 12791

For assessment of the efficacy of surgical hand disinfection, European reference method prEN 12791 prescribes that the hands must be kept wet with the reference alcohol for 3 min regardless of the applied volume. The aim of this study was to determine whether the applied volume of the reference disinfectant n-propanol (60%, vol/vol) influences the effect on the resident hand flora. Ten experiments with 200 reference disinfections were analyzed. Hands were washed for 1 min with soap. The bacterial prevalue was obtained by rubbing fingertips in tryptic soy broth for 1 min. After this, each subject treated the hands with n-propanol (60%, vol/vol) by using as many portions as necessary to keep hands wet for a total of 3 min. Bacterial postvalues (immediate effect) were obtained for one hand, and the other hand was gloved for 3 h. After the gloves were taken off, a second postvalue was obtained (sustained effect). Most surgical reference disinfections (73%) were achieved with 9 ml of the reference alcohol, followed by 12 ml (24%) and 6 ml (3%). There was no significant difference between the mean log10 reduction values for the three treatment groups, both in terms of the immediate effect (P = 0.333, as determined by analysis of variance) and in terms of the sustained effect (P = 0.442). A higher number of portions did not correlate with a higher reduction factor (for immediate effect, Pearson's correlation coefficient = -0.028 [P = 0.689]; for sustained effect, Pearson's correlation coefficient = 0.059 [P = 0.404]). If the hands were kept wet with the reference alcohol for the total application time, the applied volume could vary, but this did not alter the efficacy.