Data analysis

The CFU counts per RODAC plate were described as a median (interquartile range, IQR) due to the expected skewed distribution of these values. Median baseline CFU counts were compared between the different devices using a Mann-Whitney U test. Median baseline and post-disinfection CFU counts were compared using a Wilcoxon signed rank test for each of the three devices separately. We chose to display the absolute reduction in CFU since the number of CFU in the baseline measurements was too low to calculate reliable Log-reductions. We discarded RODAC/CFU counts for both the baseline and post-disinfection test if either of the test results could not be used due to contamination or other errors. Disinfection of materials should reduce the number of CFU to below the detection level. The following thresholds for contamination (based on hospital standards) were used: low level of contamination (<10 CFU/RODAC), moderate contamination (10–50 CFU/RODAC) and high level of contamination (≥50 CFU/RODAC).