How Effective Are Cleaners With “Effective Microorganisms”?

ABSTRACT Microbial‐based cleaning products containing active microorganisms, such as Bacillus spores and “Effective Microorganisms” (EM)—a blend of lactic acid bacteria, photosynthetic bacteria, and yeast—are marketed for their potential to clean and displace pathogens. This study evaluated the efficacy of EM‐based cleaners by analyzing their microbial composition with MALDI‐TOF and metagenomics, testing their cleaning power according to industry standards, and assessing antimicrobial effects per DIN EN 13697. Additionally, co‐cultivation tests and simulations of repeated application were conducted using both EM cleaners and EM solutions in a reference cleaning formula. The findings revealed that three out of five EM‐based cleaners performed similarly or worse than the IKW reference cleaner. In co‐culture experiments, the initial EM concentration was crucial for microbial establishment. Undiluted EM showed limited activity against Staphylococcus aureus , Escherichia coli , and Serratia marcescens but coexisted with Aspergillus brasiliensis without dominance. No EM growth was detected in the presence of Candida albicans . Simulated repeated application on soiled surfaces confirmed that EM did not enhance or impair cleaning efficacy, nor did it lead to lasting colonization on surfaces. Overall, while EM cleaners demonstrated some antimicrobial effects under specific conditions, they did not achieve superior cleaning or persistent microbial control compared to standard formulations.