Biofilm formation and susceptibility to biocides of recurring and transient Escherichia coli isolated from meat fabrication equipment

© 2018Some Escherichia coli can persist on meat fabrication equipment, thus becoming a recurring source of contamination for meat. This study investigated the potential mechanism by which E. coli persist, by comparing the susceptibility to disinfectants and biofilm forming ability of two populations, recurring and transient, each consisting of 50 E. coli isolated from meat fabrication equipment. Susceptibility to three commercial disinfecting agents, biocide A (a quaternary ammonium compound based sanitizer), B (a sodium hypochlorite based sanitizer), and C (a chlorinated alkaline cleaner) was assessed, by determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Biofilm developed on polystyrene surface for up to 6 days at 15 °C was quantified by crystal violet staining. We found the recurring population did not have higher (P > 0.05) MICs or MBCs of any of the three biocides than the transient population, and the maximum MBCs were well within the respective in-use concentrations of the disinfectants. The development of biofilms was time-dependent for both transient and recurring E. coli populations and was correlated with motility and curli expression. Of the recurring E. coli, 50, 86, and 88% developed strong biofilms by days 2, 4, and 6, respectively. Of the transient E. coli, 58, 82 and 84% did so. The transient group had a higher (P < 0.05) fraction of isolates that did not form measureable biofilms by day 6. All E. coli in biofilms were able to survive and recover after the treatment of QAC at 200 ppm, irrespective of their groups. The findings of this study suggest that biofilm forming ability may play a role in the persistence of E. coli on equipment surface and the persistence would be unlikely associated with biocide tolerance.