Purpose: Evaluate the biofilm-forming capacity of E. coli O26 isolates, determine whether motility, extracellular matrix (ECM) components and bacterial adhesion to hydrocarbons are factors associated with biofilm formation, and evaluate the sensitivity of isolates to food industry approved sanitizers.
Methods: Forty E. coli O26 isolates, comprising 27 EHEC, eight aEPEC, two NTEC and three pEHEC were assessed for their capacity for biofilm formation on polystyrene and at the air liquid interphase under static conditions. Motility, extracellular matrix (ECM) components, and bacterial adhesion to hydrocarbons were also investigated. Finally, the efficacy of three commercially available sanitizers against E. coli O26 biofilms was determined.
Results: EHEC isolates were significantly more likely to form biofilms after 48 hours than aEPEC isolates. However, no differences were observed after 72 hours with 28 of 40 (70%) isolates demonstrating biofilm formation. EHEC isolates (63%) were significantly more likely to form a pellicle at the air liquid interphase than aEPEC isolates (0%). Isolates that were motile and expressed ECM components (55%) generated biofilms with significantly greater cell densities than those isolates that were nonmotile and/or did not express ECM components. Overall, no correlation was found between hydrophobicity and biofilm formation. The application of sanitizer resulted in mean reductions in cell density of 0.56 and 0.16 log CFU/ml after 2 and 10 min treatments, respectively.
Significance: EHEC isolates show enhanced capacity to rapidly develop biofilms. The protective advantage that results from biofilm formation may contribute to the frequent association of these isolates with foodborne illness.