An enhanced, statistically repeatable method for screening antimicrobial formulations in laundry applications, an adaptation of BSI EN 17658

Abstract

There is an increasing need for reliable methods to measure the reduction of microorganisms during the domestic laundering process. An enhanced throughput (ETP) methodology, an adaptation of the European standard BS EN 17658:2022, was developed as a screening tool for evaluating experimental laundry formulations with improved capacity and efficiency. The modifications include the replacement of a lab-scale tumbling device with a more compact and affordable instrument along with additional procedural modifications to simplify the test procedure without compromising the critical parameters such as mechanical action, bioburden, liquor ratio and soil. The ETP method was utilized to replicate the rinse cycle test from an international ring trial, where the participating laboratories assessed the efficacy of 0.04% Dodecyl dimethylammonium chloride (DDAC) as a benchmark standard. In addition, an experimental formulation was evaluated according to ETP and the full EN standard against the five required microorganisms including Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Enterococcus hirae and Candida albicans. Overall, the average log reduction values obtained with both the benchmark and experimental formulation did not differ between the two methods. Furthermore, based on the benchmark data, the ETP method consistently showed lower variability within a lab than the EN method, as evaluated in the ring trial. The advantages and weaknesses of ETP as a research screening tool are also discussed in this work.