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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 10/1/2007 Publication Date: 10/11/2007 Citation: Uhlich, G.A. 2007. Characterization of Shiga toxin-producing Escherichia coli isolated from different sources in 2006. Meeting Abstract. Interpretive Summary: Technical Abstract: Recently, we characterized strains from the spinach and leafy green vegetable outbreaks of 2006, including a serotype O157:H7 strain that was identical to the strain determined to be responsible for the disease outbreak and an E. coli serotype O-:H4 strain. Both were isolated from the same bag of spinach. We demonstrated that, on glass slides, the O-:H4 strain produced large amounts of biofilm that was extremely resistant to physical stresses, while the serotype O157:H7 strain failed to produce visible biofilm, but rather formed only loose attachments on glass that could be completely dislodged by mild agitation. However, in mixed biofilm studies, the E. coli O157:H7 strain was able to persist on glass along with the serotype O-:H4 biofilm in numbers even greater than those for the O-:H4 strain and was equally resistant to physical removal as the O-:H4 strain. These findings are important as they suggest that strains of E. coli O157:H7 that exist in food environments as members of a population, may be able to work synergistically with other bacteria in that community to form extremely tough and physically resistant biofilms. In continuing studies, we are investigating the pathways used for biofilm formation by the O157:H7 and O-:H4 strains using non-polar gene deletion strains. Preliminary results indicate that the O-:H4 strain uses a CsgD controlled pathway which generates cellulose as a major exopolysaccharide. Subsequent studies will identify the factors responsible for augmentation of O157:H7 biofilm formation in mixed cultures with certain other enterobacteriacea. |
