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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #322101
Title: Aggregative adherence fimbriae I (AAF/I) mediate colonization of fresh produce and abiotic surface by Shiga toxigenic enteroaggregative Escherichia coli O104:H4

Author
item Nagy, Attila
item Bauchan, Gary
item Shelton, Daniel
item Nou, Xiangwu
item XU, YUNFENG - Northwest Agriculture And Forestry University

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2016
Publication Date: 4/12/2016
Citation: Nagy, A., Bauchan, G.R., Shelton, D.R., Nou, X., Xu, Y. 2016. Aggregative adherence fimbriae I (AAF/I) mediate colonization of fresh produce and abiotic surface by Shiga toxigenic enteroaggregative Escherichia coli O104:H4. International Journal of Food Microbiology. 229:44-51.

Interpretive Summary: E. coli O104:H4 is a newly emerged potent foodborne pathogen that produces Shiga toxin and also a special type of fimbriae (cell surface appendage) that allows the cells to form thick biofilms (collection of attached bacteria) on the human large intestine. This study was conducted to determine if these fimbriae were also involved in adherence and colonization of produce (spinach) and abiotic surfaces. A mutant strain was created from the wild type strain by deleting the gene encoding for the fimbriae. The mutant and wildtype strains were compared for their ability to adhere to and form biofilms on spinach and on glass surfaces. We observed that the mutant strain lost the ability to colonize and form biofilms on both of these surfaces. These findings will be important for understanding the survival and persistence of this emmeging and potent foodborne pathogen in food and environmental matrices, including fresh produce. This information will be of interest to other scientists, the produce industry and regulatory agencies.

Technical Abstract: The Shiga toxigenic Escherichia coli O104:H4 bares the characteristics of both enterohemorrhagic (EHEC) and enteroaggregative (EAEC) E. coli. It produces plasmid encoded aggregative adherence fimbriae I (AAF/I) which mediate cell aggregation and biofilm formation in human intestine and promote Shiga-toxin adsorption, but it is not clear whether the AAF/I fimbriae are involved in the colonization and biofilm formation on food and environmental matrices such as the surface of fresh produce. We deleted the gene encoding for the AAF/I fimbriae main subunit (AagA) from an outbreak associated E. coli O104:H4 strain, and evaluated the role of AAF/I fimbriae in the adherence and colonization of E. coli O104:H4 to spinach and abiotic surfaces. The deletion of aagA gene did not affect the adherence of E. coli O104:H4 to these surfaces. However, it severely diminished the colonization and biofilm formation of E. coli O104:H4 on these surfaces. Strong aggregation and biofilm formation on spinach and abiotic surfaces were observed with the wild type strain but not the isogenic aagA deletion mutant, suggesting that AAF/I fimbriae play a crucial role in persistence of O104:H4 cells outside of the intestines of host species, such as on the surface of fresh produce.