The FDA is conducting an assignment to collect romaine lettuce samples from commercial cooling operations in Yuma County, Arizona during the current harvest season to test for microbial hazards repeatedly linked to foodborne illnesses associated with the leafy vegetable.
The agency began this sampling assignment in February, 2021, and plans to continue its collection and testing into April, 2021, through to the end of the harvest season in the Yuma growing region. All samples are being tested for Salmonella spp., Escherichia coli O157:H7, and other Shiga toxin-producing E. coli (STEC).
The FDA has conducted ongoing surveillance of romaine lettuce from the Yuma County agricultural region following the spring 2018 multistate E. coli O157:H7 outbreak of foodborne illness linked to romaine lettuce from the area. This assignment also is part of a larger effort by the FDA, known as its Leafy Greens STEC Action Plan, to help ensure the microbiological safety of leafy vegetables.
Yuma and Romaine Lettuce
Yuma is known as the nation’s “winter salad bowl” because most of the leafy greens and other vegetables eaten by U.S. consumers in the winter and early spring, including romaine lettuce, are grown in the region. California’s Imperial Valley growing region also produces a large portion of the leafy greens eaten in the U.S. during the same period.
Romaine lettuce is grown low to the ground and thus is susceptible to contamination from irrigation water splashing off the soil. Typically planted in rows, romaine lettuce grows in a tall head of sturdy leaves with a firm rib at the center of the shoot. The crop may be harvested by machine or by hand. Romaine lettuce is typically eaten without having undergone a ‘kill step,’ such as cooking, to reduce or eliminate bacteria.
The FDA plans to collect 500 samples of romaine lettuce for this assignment. Each sample will consist of 10 subsamples, and each subsample will be made up of at least 300 grams of romaine lettuce (whole heads, hearts or individual leaves).
All the collection sites are in Yuma County. The FDA will only collect samples grown in Yuma County, from FDA-regulated commercial cooler and cold storage facilities where field heat is removed from harvested romaine and the product is cold stored prior to processing and shipment. Samples may be collected prior to or following cooling. The focus on commercial cooling operations for purposes of sample collection follows a similar model used during an assignment conducted in FY19. This approach enables the FDA to collect samples more efficiently, from multiple farms at centralized locations.
See detailed information on what to expect when the FDA collects samples.
The FDA will preannounce its visits to firms. The agency is taking additional precautions to ensure the safety of personnel and the integrity of its sample collection in light of COVID-19. Agency field staff have undergone training to help ensure their safety and the safety of firm employees and will be outfitted with personal protective equipment, consistent with all state, local and applicable CDC guidance.
All samples will be tested for E. coli O157:H7 and other STEC as well as Salmonella spp.
The FDA has contracted with an independent laboratory near the collection sites to conduct the testing. The use of this laboratory will significantly reduce the time between sample collection and the reporting of test results, minimizing economic losses associated with products that test negative for pathogens.
The FDA anticipates receiving the test results within 24 hours of the laboratory receiving the samples, after which the FDA will relay the results to the firm(s). The agency anticipates that it will be able to notify firms of negative results and presumptive positives, also called “can’t-rule-out” (CRO) samples, within 24 hours of the samples’ arrival at the laboratory. The FDA will notify firms of positive samples once confirmed.
When a pathogen is detected, the FDA will notify both the operator of the commercial cooler from which it was collected and the management of the farm where it originated. The FDA will work with them, as well as with state regulatory partners, to take action as warranted to protect the public health, and identify the cause of the contamination. Enforcement activities may include actions to correct and prevent microbial contamination or to remove violative food from the market, as necessary. Additionally, whole genome sequencing (WGS) will be conducted on detected pathogens to identify the organism’s genetic pattern and determine whether it may be linked to known human illness events.
The FDA understands that industry may choose to hold the sampled lots pending notification of test results and supports this action to help prevent recalls of any contaminated lettuce that could have entered commerce. The agency’s focus on commercial cooling operations for purposes of sample collection is expected to facilitate traceback, if needed, because in most cases the agency will know the identity of the farm associated with the sample(s).
Consistent with the FDA’s Leafy Greens STEC Action Plan, the agency will engage with industry on conducting root cause analyses for any positive samples found during this assignment. Root cause analyses are important in that they seek to identify potential sources and routes of contamination, inform what preventive measures are needed, and prevent outbreaks of foodborne illness.
The FDA plans to publish the test results in the form of a summary report after sampling concludes and the final data are analyzed.
The agency is sensitive to the concerns of industry and strives to provide analytical results to firms as soon as they are available. The FDA will notify all firms of analytical results as soon as possible once sample analysis is complete.