Test methods for surface disinfection: comparison of the Wiperator ASTM standard E2967-15 and the 4-field test EN 16615

Aim: Two test methods for surface disinfection (phase 2, step 2) – the Wiperator method (ASTM standard E2967-15) and the 4-field test (EN 16615) – were compared using a disinfectant solution based on quaternary ammonium compounds and a ready-to-use alcohol-based wipe. As test organisms, Staphylococcus aureus and Pseudomonas aeruginosa were used. Results: While the 4-field test is a manual method and better reflects the process in practice, with the Wiperator, the wiping process is better controlled because it is an automated procedure. A comparison of the effects of both methods on the target log(10)-reduction of S. aureus and P. aeruginosa indicates a statistically significant difference between the two test methods (Mann-Whitney U-Test. S. aureus: 0 (U(min))<4 (U(crit)); n(1)=8, n(2)=8, p=0.001; 2-sided. P. aeruginosa: 24 (U(min))<26 (U(crit)); n(1)=11, n(2)=10, p=0.025, 2-sided). In addition, the results indicate that the wipe used has a major influence on the success of the disinfection process. Discussion: Both methods are suitable for efficacy studies of surface disinfectants, yet they differ in some aspects. Additionally our data indicate a statistically significant difference between the two test methods. Conclusion: Efficiency testing of surface disinfection is a complex process that depends on many different parameters. Since the 4-field test better reflects the practice, it makes sense to stick to this test procedure, taking into account that the EN 16615 was approved by CEN TC 216 in 2015 after method validation ring trials.