Investigation of a Multistate Outbreak of Listeria monocytogenes Infections Linked to Frozen Vegetables Produced at Individually Quick-Frozen Vegetable Manufacturing Facilities.

In 2016, the U.S. Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC), and state partners investigated nine Listeria monocytogenes infections linked to frozen vegetables. The investigation began with two environmental L. monocytogenes isolates recovered from Manufacturer A, primarily a processor of frozen onions, that were a match by whole genome sequencing (WGS) to eight clinical isolates and historical onion isolates with limited collection details. Epidemiologic information, product distribution, and laboratory evidence linked suspect food items, including products sourced from Manufacturer B, also a manufacturer of frozen vegetable/fruit products, with an additional illness. The environmental isolates were obtained during investigations at Manufacturers A and B. State and federal partners interviewed ill people, analyzed shopper card data, and collected household and retail samples. Nine ill persons between 2013 and 2016 were reported in four states. Of four ill people with information available, frozen vegetable consumption was reported by three, with shopper cards confirming purchases of Manufacturer B brands. Two identified outbreak strains of L. monocytogenes (Outbreak Strain 1 and Outbreak Strain 2) were a match to environmental isolates from Manufacturer A and/or isolates from frozen vegetables recovered from open and unopened product samples sourced from Manufacturer B; the investigation resulted in extensive voluntary recalls. The close genetic relationship between isolates helped investigators determine the source of the outbreak and take steps to protect public health. This is the first known multistate outbreak of listeriosis in the United States linked to frozen vegetables and highlights the significance of sampling and WGS analyses when there is limited epidemiologic information. Additionally, this investigation emphasizes the need for further research regarding food safety risks associated with frozen foods.

Integrating the Food and Drug Administration Office of the Coordinated Outbreak Response and Evaluation Network's foodborne illness outbreak surveillance and response activities with principles of the National Incident Management System.

The Food Safety Modernization Act mandates building a national Integrated Food Safety System, which represents a seamless partnership among federal, state, local, territorial, and tribal agencies. During multistate foodborne illness outbreak investigations, local and state partners, the Centers for Disease Control and Prevention, the United States Food and Drug Administration (FDA), or the United States Department of Agriculture Food Safety Inspection Service, depending on the regulated food product, become engaged and assist in coordinating the efforts between partners involved and determine the allocation of resources. The FDA Center for Food Safety and Applied Nutrition (CFSAN) Office of the Coordinated Outbreak Response and Evaluation (CORE) Network coordinates foodborne illness outbreak surveillance, response, and post-response activities related to incidents involving multiple illnesses linked to FDA-regulated human food, dietary supplements, and cosmetic products. FDA has implemented the National Incident Management System (NIMS) Incident Command System (ICS) principles across the agency to coordinate federal response efforts, and CORE has adapted NIMS ICS principles for the emergency management of multistate foodborne illness outbreaks. CORE's implementation of ICS principles has provided several benefits to the operational cycle of foodborne illness outbreak investigations, including establishing a consistent, standardized, and transparent step-by-step approach to outbreak investigations. ICS principles have been instrumental in the development of a national platform for rapid and systematic laboratory, traceback, and epidemiologic information sharing, data analysis, and decision-making. This allows for partners across jurisdictions to reach a consensus regarding outbreak goals and objectives, deploy resources, and take regulatory and public health actions.

Reduction of Escherichia coli O157:H7 viability on leafy green vegetables by treatment with a bacteriophage mixture and trans-cinnamaldehyde.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been recognized as a major foodborne pathogen responsible for frequent gastroenteritis outbreaks. Phages and essential oils can be used as a natural antimicrobial method to reduce bacterial pathogens from the food supply. The objective of this study was to determine the effect of a bacteriophage cocktail, BEC8, alone and in combination with the essential oil trans-cinnameldehyde (TC) on the viability of a mixture of EHEC O157:H7 strains applied on whole baby romaine lettuce and baby spinach leaves. The EHEC O157:H7 strains used were Nal(R) mutants of EK27, ATCC 43895, and 472. Exponentially growing cells from tryptic soy (TS) broth cultures were spot inoculated on leaves and dried. EHEC cells were placed at low, medium, and high inoculum levels (10(4), 10(5), and 10(6) CFU/mL, respectively). Appropriate controls, BEC8 (approx. 10(6) PFU/leaf), and TC (0.5% v/v) were applied on treated leaves. The leaves were incubated at 4, 8, 23, and 37 °C in Petri dishes with moistened filter papers. EHEC survival was determined using standard plate count on nalidixic acid (50 µg/mL) Sorbitol MacConkey agar. No survivors were detected when both leaves were treated with BEC8 or TC individually at low inoculum levels after 24 h at 23 and 37 °C. When the EHEC inoculum size increased and/or incubation temperature decreased, the efficacy of BEC8 and TC decreased. However, when the two treatments were combined, no survivors were detected after 10 min at all temperatures and inoculum levels on both leafy greens. These results indicated that the BEC8/TC combination was highly effective against EHEC on both leafy greens. This combination could potentially be used as an antimicrobial to inactivate EHEC O157:H7 and reduce their incidence in the food chain.