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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR MECHANISMS OF PATHOGENIC BACTERIA INTERACTIONS WITH PLANT SURFACES AND ENVIRONMENTAL MATRICES

Location: Environmental Microbial and Food Safety Laboratory

Title: Native interaction of Escherichia coli O157:H7 and Ralstonia insidiosa in forming dual-species biofilms

Authors
item Liu, Nancy -
item Nou, Xiangwu
item Lefcourt, Alan
item Shelton, Daniel
item Lo, Y. -

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2013
Publication Date: N/A

Technical Abstract: Biofilm formation by native microflora in food processing environments can increase the risk of foodborne outbreaks by providing a protective microenvironment to foodborne pathogens. Hence the presence of strong biofilm producing bacteria in such an environment can be regarded as a risk factor. In this study, a strong biofilm forming bacterium, Ralstonia insidiosa, previously isolated from a fresh-cut produce plant was co-cultured with an Escherichia coli O157:H7 strain (EcO157, a weak biofilm former) to allow examination of the formation of dual-species biofilms at 30 and 10 oC. A “synergistic” effect was observed in biofilm formation when R. insidiosa and EcO157 were co-cultured at 30 oC in 10% TSB, as evidenced by an increase in biomass. Z-stack microscopic images revealed a significant thickening (up to 2-fold) of the biofilm formed in the presence of both bacteria when compared to the biofilm formed by R. insidiosa in momoculture. There was a significant increase of EcO157 growth (6.80±0.32 CFU/cm2) in dual-species biofilms when compared to the mono-culture (5.19±0.19 CFU/cm2), which did not form discernible biofilm under conditions tested. Results were similar when the incubation temperature was lowered to 10 oC. This increase in EcO157 numbers was correlated (P<0.01) to the increasing growth of R. insidiosa in dual-species biofilms. These results suggested that microflora native to produce processing plants can potentially enhance the survival of bacterial pathogens such as EcO157 by promoting their incorporation into biofilms under temperature abuse conditions or in microenvironments in plants, and thus it is critical to ensure stringent temperature control in food processing plants to inhibit biofilm formation.

Last Modified: 4/23/2014