Pathogens can be transmitted accidentally between patients or healthcare workers, however, surfaces are a reservoir for pathogens, too, and contribute to spreading of nosocomial infections [1]. Therefore, comprehensive environmental cleaning and disinfection are as important as proper hand hygiene to combat healthcare-associated infections. In this course, the correct surface disinfectant must be chosen since each surface bears its individual risk and requires a risk evaluation [2]. Customers can choose from a range of disinfectants and active substances e. g. alcohols, quaternary ammonium compounds, or active oxygen-releasing compounds.
New in the field of surface cleaning and disinfection are probiotic cleaners, which contain spores of non-pathogenic bacteria, like lactic acid bacteria or bacteria of the genus Bacillus [3]. When applied onto a surface, the bacteria germinated from the spores replace harmful pathogens by the competitive exclusion principle, i.d. by consumption of the available nutrients and thus preventing the pathogens to grow. In addition to the bacterial spores, such cleaners often contain detergents to allow for a proper cleaning of surfaces. The bacterial spores themselves are not harmful, neither for humans nor the surface material so that in the course of risk evaluation, only the detergents need to be considered.
A study from 2022 proofed that the contamination with pathogens was partially reduced on surfaces in a neurological ward by regular application of a probiotic cleaner. Furthermore, the counts of bacteria exhibiting antibiotic resistance genes decreased [4]. Beside single, planktonic cells, biofilms are a major challenge in cleaning and disinfection. Biofilms are formed from aggregating bacteria sticking to a surface and surrounded by a polymer matrix, which protects the cells from external stresses. Due to the polymer matrix biofilms are difficult to treat with cleaners or disinfectants. When probiotic cleaners were applied against bacterial biofilms, they were not as effective as conventional disinfectants or plain soap [3].
Conventional disinfectants and probiotic cleaners are both classified as biocides [5] and require an official authorisation. Despite this common classification, they can hardly be compared directly since both rely on completely different mode of actions. For example, probiotic cleaners require more time to be effective as the spores need to germinate to vegetative bacteria, which then in turn can prevent the grow of pathogens by consumption of nutrients. In contrast, disinfectants act within seconds or minutes directly after the first application. Pathogens are chemically inactivated and the risk of contamination is reduced immediately. A surface treated with a probiotic cleaner is never free from microorganisms and only by complex microbiological methods remaining pathogens could be detected after application. Conventional disinfection aims to reduce the total number of microorganisms on a surface so that it does not pose an infection risk anymore, thus, the determination of the microbiological load of a surface is a quick and easy readout for the efficacy of a disinfectant.
Conclusion
According to current knowledge, probiotic cleaners are not harmful to human or the environment. Nevertheless, as they are proofed to partially reduce pathogenic contaminations on surfaces, they are classified as biocides. Due to the lack of national or international norms for determining their efficacy and the behaviour and mode of action that differs from conventional disinfectants, probiotic cleaners are challenging to implement as alternative to conventional disinfectants and need special attention when including in the risk evaluation.
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