Persistence of non-O157 shiga-toxigenic Escherichia coli on equipment surfaces and fresh produce

Authors: Boomer, Ashley; Gu, Ganyu; Oh, Sookyung; Nou, Xiangwu; Patel, Jitendra

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2025
Publication Date: 11/27/2025
Citation: Boomer, A.M., Gu, G., Oh, S., Nou, X., Patel, J.R. 2025. Persistence of non-O157 shiga-toxigenic Escherichia coli on equipment surfaces and fresh produce. Foodborne Pathogens and Disease. https://doi.org/10.1177/15353141251401726.
DOI: https://doi.org/10.1177/15353141251401726

Interpretive Summary: Shiga-toxin producing Escherichia coli (STEC) have been associated with outbreaks of foodborne illnesses due to contamination of fresh produce. The disease-causing bacteria can adhere to each other and a surface to form a biofilm, and in such a configuration, the bacteria are hard to kill and remove with commonly used disinfectants. Further, they can also attach to fresh produce leaves and persist for a longer time. We used a bioreactor to evaluate biofilm formation of 12 non-O157 STEC strains on surface material most frequently used for food processing equipment. These surfaces included stainless steel, polycarbonate, a type of plastic, and Teflon. The persistence of these strains on cabbage, romaine lettuce and spinach leaves were also investigated. In general, these bacteria formed weaker biofilms on stainless steel surfaces compared to other surfaces. Persistence of these strains was dependent on the temperature at which fresh produce was stored. Bacteria persisted in lower numbers when stored at low temperature. Stainless steel was better in minimizing bacterial contamination evident from the least number of bacterial adherence to this surface. These findings highlight the significance of an effective sanitation regime to minimize contamination of fresh produce. The information is useful to U.S. fresh produce processing and packing industries to reduce food safety risks.

Technical Abstract: The illnesses attributed to non-O157 Shiga toxin-producing Escherichia coli (STEC) have increased in the past decade. Fresh produce has been implicated in those outbreaks. Biofilm formed by non-O157 STEC on the equipment surfaces are resistance to disinfectant and could be a potential public health hazard to cross-contaminate food products. The purpose of this study was to evaluate the biofilm formation ability of non-O157 STEC on equipment surfaces. Further, the persistence of non-O157 STEC on fresh produce surfaces was investigated. Twelve non-O157 serotypes (O26, O45, O103, O111, O121, O145) were evaluated for biofilm formation on equipment surfaces (polytetrafluoroethylene, polycarbonate, and Stainless Steel) using CDC reactor for a 48h incubation. The attachment and persistence to fresh produce (cabbage, Romaine lettuce, spinach) leaves were studied by inoculating disk-shaped fresh produce pieces (22-mm dia) with 50 µL (10 micro-droplets of 5 µL each) of actively growing cultures, followed by storage at 4, 10, and 22°C for 48 h and bacterial populations were analyzed at 0, 1, 4, 24, and 48 h by spiral plating on selective media. Biofilm formation of non-O157 STEC on equipment surfaces varied with surface and strains. In general, lower non-O157 STEC populations were recovered from SS surfaces than from PTFE or PC surfaces. Persistence of non-O157 serotypes varied with produce surface and incubation temperature. Recovery of attached STEC was 2-3 log CFU/g lower from their initial populations (~6.5 log CFU/g) when fresh produce was incubated for 24-48 h. Significant reductions in STEC populations were observed when spinach was incubated at 22 °C for 48 h. Persistence of non-O157 serotypes varies among STEC serotypes, produce surface, and incubation temperature. Bacterial attachment on produce surface is a quite complex phenomenon and its knowledge will be helpful in the evaluation of contamination risk during processing and storage of fresh produce.