Characterizing microbial cross-contamination on large surfaces using a traditional “cloth and bucket” disinfection method

Abstract

Use of buckets containing soiled disinfectant solutions for disinfection is regularly practiced in food service and other settings. This study characterized microbial transfer of vegetative bacteria (Listeria innocua and Escherichia coli), spores (Bacillus cereus), and a virus (MS2 bacteriophage), to large surfaces, using a “cloth and bucket” method with a commonly used quaternary-ammonium compound (QAC) disinfectant (with or without 5% soil) and a phosphate-buffered-saline (PBS) control. We also characterized concentrations of organisms in the bucket solutions after wiping. With disinfectant (with or without soil), there was little transfer of vegetative bacteria. Transfer occurred readily with the PBS control (4.8 ± 1.0 and 3.3 ± 0.9 log CFU/surface for Listeria innocua and Escherichia coli, respectively). Spores were transferred efficiently, regardless of whether PBS or QAC was used or whether test was with or without soil (range, 6.5 to 7.8 log CFU/surface). MS2 bacteriophage appeared to be eliminated relatively quickly. When the QAC did not inactivate the organism (regardless of soil load), high microbial loads (> 87.9% of initial inoculum) were detected in the bucket solution after wiping experiments. This study suggests that reusable cloth can potentially promote contamination of surfaces, sometimes in the presence of disinfectant. This is concerning for food service and other settings in which disinfection practices rely on the cloth and bucket system.