Curli Production Influences Cross-contamination by Escherichia coli O157:H7 When Washing Fresh-cut Romaine Lettuce. 2023

Ann Charles Vegdahl, and Donald W Schaffner
Cornell University, Department of Food Science, Geneva, NY 14456, USA; Rutgers University, Department of Food Science, New Brunswick, NJ 08901, USA. Electronic address: acv45@cornell.edu.

Escherichia coli O157:H7 expresses extracellular proteins called curli that are essential for surface colonization. Transfer rates of E. coli O157:H7 0018+ (curli+), and 0018- (curli-) from inoculated to noninoculated lettuce pieces during washing were quantified in this study. Romaine lettuce pieces were inoculated with ∼6 log CFU on just the surface, just the cut edges, or both surface and cut edges. Samples were dried for 2 h in a biosafety cabinet and then washed with ten (10) noninoculated lettuce pieces in 500 mL of water for 30 s. The curli- strain was more readily removed (3 log reduction) compared to the curli+ (1 log reduction) when only the lettuce surface was inoculated (p > 0.05). The same was true when only the lettuce piece edge was inoculated (p > 0.05), although the magnitude of the reduction was less. There was no significant difference in reduction of curli+ strain between any of the surfaces. There was a significant difference (p < 0.05) in reduction of the curli- strains when comparing the leaf surface (more removal) to the cut leaf edge (less removal). The curli+ strain always showed significantly (p < 0.05) more transfer to noninoculated leaves regardless of the inoculation location. The curli+ strain transferred about -1 log percent (∼0.1%) to noninoculated pieces, while the curli- strain transferred about -2 log percent (∼0.01%) CFU to the noninoculated pieces. Mean log percent transfer was not significantly different within the curli+ or curli- experiments (p > 0.05). When the leaf surface was inoculated, there was about 2 log percent (i.e., close to 100% transfer) into the wash water for both the curli+ and curli- strains. When only the cut edges or surface and edge were inoculated, observed mean transfer rates were lower but not significantly different (p > 0.05). Further research is needed to more fully understand the factors that influence bacterial cross-contamination during the washing of fresh produce.

UI MeSH Term Description Entries
D005506 Food Contamination The presence in food of harmful, unpalatable, or otherwise objectionable foreign substances, e.g. chemicals, microorganisms or diluents, before, during, or after processing or storage. Food Adulteration,Adulteration, Food,Adulterations, Food,Contamination, Food,Contaminations, Food,Food Adulterations,Food Contaminations
D005511 Food Handling Any aspect of the operations in the preparation, processing, transport, storage, packaging, wrapping, exposure for sale, service, or delivery of food. Food Processing,Handling, Food,Processing, Food
D005516 Food Microbiology The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept. Microbiology, Food
D014867 Water A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Hydrogen Oxide
D015169 Colony Count, Microbial Enumeration by direct count of viable, isolated bacterial, archaeal, or fungal CELLS or SPORES capable of growth on solid CULTURE MEDIA. The method is used routinely by environmental microbiologists for quantifying organisms in AIR; FOOD; and WATER; by clinicians for measuring patients' microbial load; and in antimicrobial drug testing. Agar Dilution Count,Colony-Forming Units Assay, Microbial,Fungal Count,Pour Plate Count,Spore Count,Spread Plate Count,Streak Plate Count,Colony Forming Units Assay, Microbial,Colony Forming Units Assays, Microbial,Agar Dilution Counts,Colony Counts, Microbial,Count, Agar Dilution,Count, Fungal,Count, Microbial Colony,Count, Pour Plate,Count, Spore,Count, Spread Plate,Count, Streak Plate,Counts, Agar Dilution,Counts, Fungal,Counts, Microbial Colony,Counts, Pour Plate,Counts, Spore,Counts, Spread Plate,Counts, Streak Plate,Dilution Count, Agar,Dilution Counts, Agar,Fungal Counts,Microbial Colony Count,Microbial Colony Counts,Pour Plate Counts,Spore Counts,Spread Plate Counts,Streak Plate Counts
D018545 Lactuca Any of the various plants of the genus Lactuca, especially L. sativa, cultivated for its edible leaves. (From American Heritage Dictionary, 2d ed) Iceberg Lettuce,Lactuca sativa,Lettuce,Iceberg Lettuces,Lettuce, Iceberg,Lettuces,Lettuces, Iceberg
D019453 Escherichia coli O157 A verocytotoxin-producing serogroup belonging to the O subfamily of Escherichia coli which has been shown to cause severe food-borne disease. A strain from this serogroup, serotype H7, which produces SHIGA TOXINS, has been linked to human disease outbreaks resulting from contamination of foods by E. coli O157 from bovine origin. E coli O157,E coli O157-H7,Escherichia coli O157-H7

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