Efficacy of disinfectants against Cronobacter biofilm on plastic surfaces

In this study, efficacy of benzalkonium chloride (BC), peroxyacetic acid (PAA) and chlorine dioxide (CD) against Cronobacter biofilm were evaluated on polystyrene surface. A pool of three strains of Cronobacter was grown to form biofilm in tryptic soy broth at 30 degrees C in polystyrene specimen containers. Six-days-old biofilms on containers were treated with two different concentrations (100 and 400 mg/l) of disinfectants up to 15 min at room temperature. Cell killing effectiveness and biofilm removing capacity of disinfectants were evaluated by XTT and crystal violet assays, respectively. Exposure of Cronobacter biofilm to BC, PAA and CD at 400 mg/l for 15 min caused reductions of 69, 73 and 51% in the level of viable cells, respectively. Treatments at 400 mg/l for 15 min were only able to remove up to 18% of the biofilm biomass. Results show that disinfectants routinely used in food industry are insufficient in removing of Cronobacter biofilm from plastic surfaces. Results also show that cell killing effectiveness of disinfectants is considerably restricted by the matrix of biofilm.