External Summary Report: FY 2013 Inspection, Environmental Sampling and Sample Collection (Pre and Post-Process) at Cantaloupe Packinghouses Assignment (DFPG #13-19)

Update on Listeria monocytogenes and Cantaloupes

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Food and Drug Administration


July 27, 2015



Michael Mahovic, Consumer Safety Officer
CFSAN/OFS/ Division of Produce Safety, HFS-317
Through: Samir Assar, Director, Division of Produce Safety


Summary Report: FY 2013 Inspection, Environmental Sampling and Sample Collection (Pre and Post-Process) at Cantaloupe Packinghouses Assignment (DFPG #13-19)


Amy Barringer
Director, Division of Field Programs and Guidance


An outbreak of listeriosis (an invasive illness caused by the bacterial pathogen Listeria monocytogenes (L. monocytogenes), characterized by a high case-fatality rate of approximately 20%) in late 2011 was linked to the consumption of fresh cantaloupe (musk- or rock-melon), from a single Colorado packinghouse.[1] This outbreak was one of the first reported links between listeriosis and the consumption of a fresh produce commodity in the United States. The outbreak sickened over 150 individuals and contributed to over 30 deaths. Since the Colorado outbreak, FDA surveillance sampling programs added L. monocytogenes as a target pathogen for testing on various produce commodities leading to multiple positive samples being observed, including: sprouts, lettuce, spinach, and cantaloupe.

FDA’s 2013 cantaloupe packinghouse assignment was intended to further inform FDA of current cantaloupe packinghouse operating practices and conditions and provide data on the expected prevalence of L. monocytogenes in and on cantaloupes and within packinghouses’ food and non-food contact surfaces during packing, handling and storage. This report will discuss some of the key observations of that assignment.


For this assignment, FDA focused on firms that pack fresh cantaloupe in a packinghouse; processing facilities, growing fields, cantaloupe that are “field-packed,” and firms that do not handle cantaloupe were considered out of scope. Outreach to States and to industry trade organizations was conducted prior to the execution of this assignment, discussing the scope, intent, and general procedure, and a letter to the industry announcing FDA’s intent to conduct this assignment was published in February 2013.[2] While the identity of specific firms that would be visited was not revealed during pre-assignment outreach, firms selected for inspection were notified 24 hours in advance that an inspection would take place. From each firm, FDA collected environmental and product samples of cantaloupe before and after packing; and utilized a standardized questionnaire tailored for cantaloupe packinghouses to collect information and observations about each firm. Additionally, State counterparts/officials were invited to participate and work with FDA in conducting the inspections under this assignment.

FDA does not have a complete inventory of cantaloupe packinghouses; most packinghouses that are co-located with growing operations do not have to register with the FDA. FDA initially identified more than 50 packinghouses from 18 states that potentially met the scope of this assignment. FDA attempted to achieve a distribution of firms for the assignment that would serve as a representative subsample of the domestic cantaloupe packing industry. Internal and external databases and other data sources were used to identify a list of potential firms for this assignment; the list of firms was further vetted for accuracy based on the scope of the assignment. The vetting process resulted in a decrease in the number of viable firms included for inspection under this assignment.

During implementation of the assignment, many of the selected firms were discovered to no longer be in business or handling cantaloupes. Still others did not fit the scope of the assignment (e.g., were field-pack operations or acted as distributors only). Inspections were ultimately conducted and completed at 17 of the over 50 initially identified firms.

Packinghouses handling raw agricultural commodities such as fresh cantaloupes on farm are typically exempt from the regulation in 21 CFR 110, Current Good Manufacturing Practice in Manufacturing, Packing, or Holding Human Food. However, the Federal Food, Drug, and Cosmetic Act does apply to entities that grow, harvest, pack, and distribute produce. The assignment included, in part, an evaluation of the firms’ production practices and documentation of insanitary practices that could lead to production and distribution of adulterated food.


As a general matter, the observed conditions and practices at the firms FDA inspected under this assignment aligned with recommended good agricultural practices. Some specific issues FDA observed included: several firms had food contact surfaces that were not cleanable, often due to construction with damaged, corroded, or porous materials; build-up of debris (dirt and damaged plant material) on equipment; hand washing facilities in inappropriate locations; and drain valves left open during work hours allowing water drained from a dump tank to pool outside adjacent to a partially-enclosed packinghouse. In cases where these observations were made, all firms submitted corrective action plans.

With respect to our sampling, at 8 of the 17 firms inspected, product and environmental samples were negative for Listeria. At 8 other firms inspected, environmental and produce samples were collected that yielded non-pathogenic Listeria species only; occasional findings of Listeria species are not uncommon even in well-controlled food processing environments. Such findings do, however, suggest the potential for L. monocytogenes to be present, and further demonstrate both the efficacy of good agricultural practices in avoiding establishment of L. monocytogenes populations, and the need to maintain vigilance in adhering to good agricultural practices to further avoid such establishment in the future. At one firm, we detected L. monocytogenes in two subsamples, both collected from the surface of a cantaloupe conveyance in a single location.

FDA observed that all firms inspected under this assignment had food safety plans and standard operating procedures focused on minimizing the risk of hazard introduction. We also observed that: all firms inspected had active and appropriate pest control programs; firms using dump or flume tanks had sanitizers and sanitizer monitoring programs; and, over half of the firms had environmental monitoring programs. Also of note is that all firms stated that they were aware of the aforementioned cantaloupe outbreak and took some action to evaluate or bolster their own operations, from re-evaluating their own food safety plans, to completely refitting their buildings.

FDA recognized that several firms and trade organizations acted proactively to assess and improve practices at cantaloupe packing operations as a result of the outreach before the assignment began. We expect this may have had a positive impact on our findings, as at least one of the firms visited appeared to be operating under enhanced procedures that were not historically representative of their standard methods. The fact that these firms were aware that an FDA inspection was imminent may have contributed to the quality of practices observed during inspections conducted under this assignment.

Improvements have been made by the cantaloupe industry as a result of the 2011 outbreak and subsequent FDA activities. These improvements, as well as continued FDA and industry research and outreach on cantaloupe safety, should lead to fewer contaminated cantaloupes in the marketplace with an expected reduction of risk to public health.

Assignment Strategy

FDA is aware that cantaloupes may be sporadically contaminated in the field with L. monocytogenes. However, FDA’s sampling strategy was designed to identify L. monocytogenes that had become established in the packing environment (i.e., resident L. monocytogenes). The inspection strategy was designed to identify the conditions and practices that contribute to establishment of L. monocytogenes in the packing environment as well as the conditions and practices likely to result in the contamination of cantaloupe with L. monocytogenes and the growth of L. monocytogenes during packing and storage. The presence of resident L. monocytogenes in a packing house can significantly increase the likelihood of contamination of product, and therefore the likelihood that contaminated product would be consumed, resulting in human illness.

Current Activities and Follow Up

FDA has previously published multiple documents on good agricultural practices for the fresh produce industry, including a draft commodity specific guidance for melons,[3] letters to the melon industry following significant events,[2][4] and results of environmental assessments at firms implicated in outbreaks.[1][5]

FDA participated in several meetings, with industry, academia, and state regulatory and cooperative extension partners in attendance, to share the results of this assignment. We anticipate that representatives from these organizations will further disseminate lessons learned from this assignment to cantaloupe firms, on an individualized level, and in a locally appropriate manner to help cantaloupe firms best understand and adhere to good agricultural practices.

FDA will factor the results of this assignment into continued follow-up activities regarding the safety of cantaloupe.

[1] Factors Potentially Contributing to the Contamination of Fresh Whole Cantaloupe Implicated in a Multi-State Outbreak of Listeriosis 

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