Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #322092

Title: Ralstonia insidiosa serves as bridges in biofilm formation by foodborne pathogens Listeria monocytogenes, Salmonella enterica, and enterohemorrhagic Escherichia coli

item Bauchan, Gary
item Nou, Xiangwu

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2016
Publication Date: 6/1/2016
Citation: Liu, N., Bauchan, G.R., Francoeur, C.B., Shelton, D.R., Lo, M., Nou, X. 2016. Ralstonia insidiosa serves as bridges in biofilm formation by foodborne pathogens Listeria monocytogenes, Salmonella enterica, and enterohemorrhagic Escherichia coli. Food Control. 65:14-20.

Interpretive Summary: Processed foods are susceptible to contamination by bacterial pathogens because some bacteria are able to form biofilms (communities of bacteria that adhere tenaciously to processing surfaces). We previously documented that a common environmental non-pathogenic strain, Ralstonia insidiosa, was able to form biofilms on produce and abiotic surfaces. Furthermore, it was observed that other bacteria that were pathogenic (E. coli O157:H7) and unable to form biofilms, readily became incorporated into and proliferated in pre-formed Ralstonia biofilms. In this study we evaluated the ability of other bacterial food-borne pathogens, including Listeria monocytogenes, Salmonella and additional strains of E. coli, to integrate into R. insidiosa biofilms. We observed that most of the examined pathogenic strains were able to adhere to R. insidiosa and proliferate in the co-culture biofilms. We also determined that this effect was dependent on cell to cell contact. These findings highlighted the significance of biofilm forming environmental bacteria species that may increase the survival of foodborne bacterial pathogens and therefore should be considered in developing and evaluating food safety practices. This information will be of interest to other scientists, the produce industry and regulatory agencies.

Technical Abstract: Biofilm formation on abiotic surfaces in fresh produce processing facilities might play a role in foodborne outbreaks by providing protective microniches for pathogenic bacteria. Our previous study showed that a strain of Ralstonia insidiosa isolated from a fresh produce processing plant could enhance the incorporation of E. coli O15:H7 in biofilms under various environmental conditions. These results raised the concern that R. insidiosa might have the ability to incorporate other foodborne pathogens and promote their survival and growth in biofilms. To test the hypothesis, 5 strains of Shiga toxin producing E. coli, 2 strains of Salmonella spp., and 6 Listeria monocytogenes were examined for dual-species biofilm formation with R. insidiosa. Enhanced presence in the biofilms by the pathogens was seen in 11 of 13 R. insidiosa-pathogen combinations. Synergistic increase of biomass, however, was observed in 8 of the 13 combinations. The synergistic interactions between R. insidiosa and tested foodborne pathogens seemed dependent on intimate cellular contact between the two strains. Overall, this study showed that R. insidiosa could enhance the incorporation into biofilms of different types of foodborne pathogenic bacteria and should be considered as a bridging bacterium for biofilm formation in various food processing environments.