Biocontrol of Escherichia coli O157:H7 by Enterobacter asburiae AEB30 on intact cantaloupe melons

Authors: Tran, Thao; Lee, Sangin; Hnasko, Robert; McGarvey, Jeffery - Jeff

Submitted to: Microbial Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2024
Publication Date: 3/11/2024
Citation: Tran, T.D., Lee, S., Hnasko, R.M., McGarvey, J.A. 2024. Biocontrol of Escherichia coli O157:H7 by Enterobacter asburiae AEB30 on intact cantaloupe melons. Microbial Biotechnology. 17(3). Article e14437. https://doi.org/10.1111/1751-7915.14437.
DOI: https://doi.org/10.1111/1751-7915.14437

Interpretive Summary: Pathogenic bacteria such as E. coli can contaminate fresh ready to eat produce in both the pre- (before picking) and post-harvest (after picking) environments. One method to prevent pathogen contamination in both environments is called biological control, the use of a living organism to prevent other living organisms from contaminating an environment. We identified a bacterium called Enterobacter asburiae that is able to grow, persist and prevent the pathogen E. coli from growing on cantaloupe melons in both the pre- and post- harvest environments. We examined the genes contained within the Enterobacter asburiae genome and identified 10 genes associated with E. coli growth inhibition. These genes are involved in the production of compound called LPS which coats the outside of Enterobacter asburiae and may be inhibitory to E. coli growth. Our data suggest that Enterobacter asburiae can be used as an effective biological control agent for the prevention of E. coli contamination of cantaloupe melons and likely other fresh ready to eat produce.

Technical Abstract: Escherichia coli O157:H7 causes >73,000 foodborne illnesses in the United States annually, many of which have been associated with fresh ready-to-Eat produce including cantaloupe melons. In this study, we created a produce-associated bacterial (PAB) library containing >7500 isolates and screened them for the ability to inhibit the growth of E. coli O157:H7 using an in vitro fluorescence-based growth assay. One isolate, identified by 16S and whole-genome sequence analysis as Enterobacter asburiae, was able to inhibit the growth of E. coli by ~30-fold in vitro and produced zones of inhibition between 13 and 21 mm against 12 E. coli outbreak strains in an agar spot assay. We demonstrated that E. asburiae AEB30 was able to grow, persist and inhibit the growth of E. coli on cantaloupe melons under simulated pre-and post-harvest conditions. Analysis of the E. asburiae AEB30 genome revealed an operon encoding a contact-dependent growth inhibition (CDI) system that when mutated resulted in the loss of E. coli growth inhibition. These data suggest that E. asburiae AEB30 is a potential biocontrol agent to prevent E. coli contamination of cantaloupe melons in both pre-and post-harvest environments and that its mode of action is via a CDI system.