A new study analyzes antimicrobial detergents and textile chemicals in homes

The use of less bleach and lower temperatures over washing machine cycles is promoted as a result of shifting societal attitudes toward the environment. To counteract these new behaviors, limit the spread of bacteria, fungus, and viruses in the home, as well as to manage the quantity of odor-causing microorganisms on clothing, disinfectants added to detergents have become important.

The existing European standards only apply to clinical settings and are limited to the main wash cycle for these items, despite the fact that they require their evaluation using standardized procedures.

An innovative technique for evaluating the antimicrobial efficacy of detergents and textile additives in domestic settings has been statistically validated by experts from the Biost3 Research Group, led by Antoni Monleón, lecturer in the Department of Genetics, Microbiology, and Statistics of the UB. The findings demonstrate the new protocol’s viability, and the European Committee for Standardization (CEN) has been asked to adopt it as a European standard.

It is very difficult to make sure that a product works and that is a good disinfectant. We work with micro-organisms and the results of the efficacy evaluation can be very variable depending on the method, the washing machine, the temperature, and so on. That is why it is very important to publish a standardized protocol at the European level so that manufacturers of household textile disinfectants can demonstrate the efficacy of their products with a methodology that is much closer to the real situation at home.”

Antoni Monleón, Lecturer, Department of Genetics, Microbiology, and Statistics, Universidad de Barcelona

Monleón is also a Research Group Member on Biostatistics and Bioinformatics (GRBIO) integrated into the Bioinformatics Barcelona Association (BIB).

The research, which was published in the journal PLOS ONE, was done in association with Michelle Cavalleri, a member of the CEN technical committee, and a global group of industrial and testing labs, including AC Marca, Arxada, Eurofins Biolab SRL, Henkel AG & Co KGaA, Hohenstein Laboratories GmbH & Co. KG, Hochschule Niederrhein, FB textile-u Bekleidungs-technick, and Thor Especialidades S. A.

Ana Costan and Nuria Piedra, researchers at AC Marca, have overseen the standard’s creation, the experimental phase, and the data gathering.

International ring trial to simulate domestic washing conditions

The group organized an international ring trial to assess the reliability of a novel method particularly created to test the effectiveness of detergents against microorganisms in a household setting in response to the gap in the EU regulations.

The five laboratory-scale simulators of domestic washing machines were installed in the seven participating labs. Seven parameters, including the elimination of microorganisms adhering to fabrics like Escherichia coli or Staphylococcus aureus, were assessed at various concentrations of active ingredients and temperatures.

The evaluation of disinfectant efficacy in clothing is a complex process that involves many variables and the method must allow to control aspects such as temperature, contact time, or the mechanical and chemical effect separately, so that the reproducibility is more consistent.”

Antoni Monleón, Lecturer, Department of Genetics, Microbiology, and Statistics, Universidad de Barcelona

Robust and reproducible method

This assessment approach must be reliable and repeatable in order to be used as a standard practice across the industry and to simulate domestic washing procedures.

“Robustness refers to a statistical concept as a measure of the method’s ability not to be affected by small but deliberate variations in the experiment, such as using different washing machines or different temperatures. On the other hand, repeatability means that if you use the same method with the same procedure in another laboratory, you should get a similar result,” adds Monleón.

The Biost3 research team’s task was to validate the methodology from a statistical perspective and assess the robustness of the tests conducted in various facilities. They have employed statistical techniques to achieve this goal, “detect highly variable values in the experiments, an analysis of strange values for when many variables are taken into account, and graphic methods that allow the joint variability of different experimental groups to be checked,” states the researcher.

The study’s findings demonstrated that the approach was resistant to even minor changes in the experiment, demonstrating that the experiments and the new method’s repeatability were both adequate.

Additionally, they developed a new library in the R language called Diagnobatch, a software that enables extremely quick computations and may be utilized in an industrial setting.

More realistic and cost-effective testing

In comparison to the existing technique, where antimicrobials are evaluated in industrial washing machines with distinctly different properties, the new method also more accurately replicates domestic washing circumstances. “Furthermore, previous studies indicate that a lab-scale device is not significantly different from a domestic washing machine, but has an important advantage in terms of reproducibility and repeatability,” notes Monleón.

The present approach, which requires that antimicrobial efficacy be tested independently and only one microorganism per washing machine test be assessed, improves capacity and costs over this new methodology. “The new protocol allows up to 20 tests to be run simultaneously (depending on the lab-scale device) and all microorganisms are tested in the same test,” explains the researcher.

Pending approval by the European regulator

The new approach has been submitted to the European Committee for Standardization for review in order to be considered as a new European standard in view of these encouraging results.

In the mid-term, when the standard is approved by CEN, all textile disinfectants for the domestic environment to be registered will have to demonstrate their efficacy following this protocol, whose validity and robustness has been demonstrated by our team.”

Antoni Monleón, Lecturer, Department of Genetics, Microbiology, and Statistics, Universidad de Barcelona