Isolation of indigenous bacteria from a cafeteria kitchen and their biofilm formation and disinfectant susceptibility

•Bacteria isolated from a cafeteria kitchen showed strong biofilm formation capacity.•Disinfectant susceptibility changed after biofilm formation in a strain-dependent manner.•After biofilm formation, Kocuria increased the resistance to all disinfectants tested.•Multivariate analysis revealed a significant increase of relative resistance of Kocuria spp. after biofilm.

Bacterial biofilm formation in foodservice facilities is a continuous cross-contamination risk through survival and persistence despite disinfectant treatments. In this study, we evaluated biofilm formation and disinfectant susceptibility of 178 strains obtained from a cafeteria kitchen and 70 foodborne pathogens and analyzed results by multivariate data analyses. A total of 23 areas in a cafeteria kitchen were selected for bacterial isolation and identification. The capacity for biofilm formation was tested using a crystal violet assay, and disinfectant susceptibility was examined using an agar well diffusion assay and resazurin reduction assay. The most frequently isolated genera were Bacillus (33%), Acinetobacter (17%), Kocuria (12%) and Staphylococcus (5%). The genus Bacillus showed the strongest capacity of the biofilm formation. The foodborne bacteria exhibited a wide range of susceptibility to disinfectants, such as sodium hypochlorite, hydrogen peroxide, benzalkonium chloride, lactic acid and citric acid. However, the susceptibilities changed after biofilm formation in a strain-dependent manner, and the relative resistance levels changed among the isolates. Overall, this study will be a great resource for selecting and using disinfectants in foodservice facility hygienic practices.