FDA Releases Investigation Report on 2022 Salmonella Outbreak Associated with Cantaloupe

FDA released a report on a 2022 Salmonella outbreak that was linked to cantaloupe.  A recall or public health advisory had not been issued at the time because the investigation took longer than the cantaloupe was available for sale.

The investigation did not find a definitive source for the Salmonella strain found in the outbreak, although a common  packinghouse was identified.  The report does give some broad recommendations that packing houses, as well as farms, should be following.   Key among these, from my perspective, developing written procedures (SOPs) for the operation based upon reducing risk and then following these procedures with documentation.  It seems that this was the biggest knock against the firm in this investigation.

https://www.fda.gov/food/outbreaks-foodborne-illness/factors-potentially-contributing-contamination-cantaloupe-implicated-outbreak-salmonella-typhimurium
Factors Potentially Contributing to the Contamination of Cantaloupe Implicated in the Outbreak of Salmonella Typhimurium During the Summer of 2022

Full Report - https://www.fda.gov/media/167640/download

In August 2022, the U.S. Food and Drug Administration (FDA), Centers for Disease Control and Prevention (CDC), and state partners conducted an outbreak investigation into a multistate outbreak of  Salmonella Typhimurium linked to cantaloupe.
• Total Illnesses: 87
• Hospitalizations: 32
• Deaths: 0
• Last Illness Onset: September 11, 2022
• States with Cases: GA (1), IL (5), IN (17), IA (38), KY (3), MI (3), MN (4), MO (2), OH (3), SC (1), WI (10)

The outbreak response investigation found:
1) In August 2022, CDC notified FDA about a multistate cluster of Salmonella Typhimurium illnesses 
with a potential signal for melon exposures. The cases were geographically distributed in the U.S. upper Midwest.
2) The isolates in this cluster of illnesses were within 7 alleles / 11 single-nucleotide polymorphisms 
(SNPs) of two FDA soil swab samples collected from a 2020 outbreak investigation in Indiana. As a part of the 2022 investigation, FDA and state partners collected multiple samples, but none of the resulting isolates were a definitive match to the 2022 outbreak strain.
3) FDA’s 2022 traceback investigation identified 11 points of service, of which 8 traced back to a  common packinghouse. Although a common packinghouse was identified, there was no convergence to a single shipment of products, and therefore three farms that supplied the common packinghouse were identified as potential sources of cantaloupe. 

As a result of the traceback, FDA conducted investigations in Indiana at all three farms, their common packinghouse and nearby public lands. Salmonella positive environmental samples were found at each location, but none of the resulting Salmonella isolates conclusively matched the outbreak strain by whole genome sequencing (WGS). No cantaloupes were recalled and no public warning was issued due to the implicated products no longer being on the market. 

Requirements and Recommendations

The investigation did not result in the identification of a specific microbial source or route that resulted in the contamination of cantaloupes associated with this outbreak. However, the agency identified 

Salmonella spp. in on-farm, post-harvest, and off-farm environments. Aspects of the growing, harvesting,  and packing operations which could have resulted in Salmonella contamination associated with the  implicated cantaloupe melons include:

• Common Contamination Sources of Salmonella. Matching S. Newport isolates were recovered from Farm 2, Farm 3, and the melons post-harvest packing entity in this investigation, and these isolates were genetically related to clinical samples associated with a 2020 outbreak. The genetic relatedness between the 2020 outbreak isolates and those collected here provide evidence that common contamination sources and Salmonella strains could be persistent within this growing environment.

• Off-Season Land Use. As all farmland associated with this outbreak was not under consistent management or control by cantaloupe growers, investigators were unable to completely determine and evaluate a complete profile of land use hazards. However, evidence suggests that cantaloupe farms did not routinely monitor for potential food safety hazards during non-cantaloupe growing seasons, such as in the applications of untreated turkey manure to land used for the production of cantaloupe. Of note, WGS analysis revealed that Salmonella isolates collected from all farms and the associated packinghouse were genetically related both to multistate outbreaks of salmonellosis associated with melons as well as poultry-related isolates, supporting the hypothesis that the outputs from poultry operations may have contributed to these human illness outbreaks of salmonellosis. 

• Human Pathogen Reservoirs. The recovery of multiple Salmonella strains with clear association with human illness distributed widely within the growing environment may be indicative of robust human pathogen reservoirs which persist and circulate within this growing region. Considering these findings, the FDA is continuing an ongoing assessment of this region to better understand the presence of pathogens in the growing environment.

• Post-Harvest Environments. Written SOPs for cleaning and sanitation were inconsistent with the practices reported by responsible individuals at the packinghouse to the investigator, and the effectiveness of cleaning practices was not verified. Additionally, investigational findings revealed that a final step involved the use of a cleaner labeled for aiding the washing of fresh produce, with or without an antimicrobial, was used on food contact surfaces, contrary to the instructions on the label. Following proper cleaning procedures, sanitizer use on packinghouse food contact surfaces is needed to protect against the contamination of melons. Implementing the appropriate verification procedures for cleaning and sanitization practices is essential to protect against the contamination of melons in packinghouses. 

• Pathogen Population Diversity. The recovery of multiple and diverse strains of Salmonella within the immediate growing and non-growing environments suggests that the region may contain multiple reservoirs for Salmonella spp. In addition, the recovery of Salmonella spp. in the broader agricultural environment, as demonstrated by the same Salmonella Newport strain being found at Farms 2 and 3 and the packinghouse, exemplifies the complex environmental survival, proliferation, and dispersal mechanisms which can challenge food safety mitigation practices  In light of these investigation findings, FDA highlights the following recommendations and requirements applicable to firms, such as growers of melons and similar produce:

• Review current conditions and practices to determine whether they are adequate or if additional prevention measures are warranted.
• Understanding previous land use can help farms identify and address potential sources of pathogens that may affect their farming operations.
• Be cognizant of and assess risks that may be posed by adjacent and nearby land uses, especially as it relates to the presence of livestock, including poultry, and the interface between farmland, and other agricultural areas. 
• Consider additional tools such as pre-harvest and/or post-harvest sampling and testing of products  to help inform the need for specific prevention measures.
• Poultry manure, while valued for its fertilizer value, is a known reservoir for Salmonella spp.
• Proper application of a manure that has been treated with a validated and verified process to reduce pathogens (e.g. composting with time and temperature measurements) can significantly reduce the potential for the integration of Salmonella or other human pathogens into soils (as compared to the use of raw manures). 
• Inspect, maintain, and clean and, when necessary and appropriate, sanitize all food contact surfaces of equipment and tools used as frequently as reasonably necessary to protect against contamination.
• When appropriate, use EPA-approved products according to the label for cleaning and sanitizing.
• Inconsistent adherence to or deviation from existing SOPs for cleaning and sanitizing by farms can affect produce safety. Effective communication on farms about SOPs and any changes to  those SOPs can help ensure that food safety practices are being followed. 
• Root cause analyses may be useful in identifying for growers how human pathogen sources in the broader agricultural environment may contribute to contamination. 
• Improve traceability through increased digitization, interoperability, and standardization of traceability records which would expedite traceback and help remove contaminated product from the marketplace more quickly, thereby preventing further illnesses. This is not only important for growers, but also critical for shippers, manufactures, and retailers as well, to improve overall traceability throughout the supply chain.

FDA recognizes the interconnection between people, animals, plants, and their shared environment (One  Health) when it comes to public health outcomes, and we encourage collaboration among various groups in the broader agricultural community (e.g., produce growers, those managing animal operations, state  and federal government agencies, and academia) to address this issue.

FDA continues to leverage agency resources to expand the information available to growers on the 

capacity for foodborne pathogen survival, persistence, and movement in and through the agricultural 

environment. We will continue to support stakeholders’ efforts to develop ways to better understand and  mitigate the risk of contamination. Growers also have the opportunity to request on farm readiness 

reviews to better understand the PSR regulatory requirements.

Local in-depth knowledge and actions are critical in helping resolve potential routes of contamination of  cantaloupe melons in the Southwest Indiana growing region associated with this foodborne illness 

outbreak, including Knox and Gibson Counties of Indiana moving forward. FDA urges other government  and non-government entities, produce growers and trade associations to further explore possible source(s)  and route(s) of contamination associated with the outbreak pathogen and with other foodborne pathoge ns of public health significance. This information is critical to developing and implementing short- and longterm remediation measures to reduce the potential for another outbreak associated with cantaloupes or  other fresh produce commodities.

FDA will work in conjunction with the Indiana State Department of Health to increase awareness 

amongst the melon growing industry of pathogenic environmental strains in the region to develop and 

promote risk reduction strategies related to melon growing and harvesting to minimize the impact of these strains.

Food safety is a shared responsibility that involves food producers, distributors, manufacturers, retailers, and regulators. FDA is committed to working with these stakeholders to advance this critical work.