Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2010
Publication Date: 3/31/2010
Citation: Uhlich, G.A., Rogers, D., Mosier, D.A. 2010. Esherichia coli serotype O157:H7 retention on solid surfaces and peroxide resistance is enhanced by dual-strain biofilm formation. Foodborne Pathogens and Disease. 7(8):935-943. Interpretive Summary: Biofilm formation allows food-borne pathogens to persist on surfaces, resist environmental stresses, and withstand antimicrobial challenges. However, Escherichia coli serotype O157:H7 forms little biofilm on most surfaces suggesting that it may use alternative methods to survive in the environment. We showed earlier that an O157:H7 strain that was unable to form biofilm could persist in large numbers in dual-strain biofilms formed with a biofilm-forming companion strain. This study tested other companion strains with serotype O157:H7 and found that The other strains capable of biofilm formation could also retain serotype O157:H7. However, certain companion strains were more accomplished at retaining E. coli serotype O157:H7. Strains of serotype O157:H7 persisting in dual-strain biofilms were also more resistant to antimicrobials than free growing cells. This study indicates that E. coli serotype O157:H7 may persist in the environment and resist sanitizing agents by colonizing the biofilms of other bacteria. Future measures to control O157:H7 in food environments may need to include methods to identify and eliminate certain members of the resident microflora.
Technical Abstract: In a previous study we showed that an Escherichia coli O157:H7 strain that was unable to form biofilm could persist in large numbers in dual-strain biofilms formed with an E. coli O-:H4 companion strain. In this study we tested additional companion strains for their ability to retain serotype O157:H7 strain 0475s. Companion strains producing biofilm that withstood aggressive washes were able to significantly increase serotype O157:H7 persistence. Dual-strain biofilms with certain companion strains retained higher percentages of strain 0475s and that ability was independent of biofilm total cell numbers. Tests with additional non-biofilm forming serotype O157:H7 strains showed that enhancement by companion strains was not unique to strain 0475s. Experiments using an E. coli companion strain with deletions of various curli and cellulose genes indicated that dual-strain biofilm formation was dependant on companion strain properties. Strain 0475s was not able to generate biofilm or persist on plastic when grown in broth with a biofilm-forming companion but separated by a 0.2 µm porous membrane indicating a requirement for intimate contact with the companion strain. When dual-strain biofilms were challenged with 5% H2O2, strain 0475 showed greater survival in certain biofilms compared to the surrounding planktonic cells. The results of this study indicate that non-biofilm forming serotype O157:H7 strains may persist on solid surfaces by colonizing biofilms generated by companion strains. However, properties other than biofilm mass enable certain companion strains to retain greater numbers of serotype O157:H7.