The new investigative report about romaine lettuce contamination drew comments Wednesday from both FDA Commissioner Scott Gottlieb and Deputy Commissioner Frank Yiannas. The report looks at the most recent romaine E. coli outbreak, which was declared over on Jan. 9 after confirmation of 62 illnesses in 16 states and the District of Columbia, resulting in 25 hospitalizations and two cases of hemolytic uremic syndrome (HUS). There were no deaths.

Among the report’s findings are:

• The outbreak strain of E. coli O157: H7 was found in the sediment of an on-farm water reservoir in Santa Maria in Santa Barbara County, CA.
• The outbreak strain was not found anywher else in sampling done during the investigation in various California leafy greens growing areas and counties.
• FDA has concluded that the water from the on-farm water reservoir wher the outbreak strain was found most likely led to contamination of some romaine lettuce consumed during the outbreak.
• Traceback investigation analysis indicated that other ranches owned by the same farm as well as other farms may have introduced into commerce contaminated romaine lettuce or other produce items. These other farms did not use water from the water reservoir wher the outbreak strain of E. coli O157: H7 was found and the FDA was unable to identify a potential source of contamination.
• FDA has concluded that the water from the on-farm water reservoir wher the outbreak strain was found was most likely not effectively treated with a sanitizer and this may have led to contaminated water directly contacting romaine lettuce after harvest or by the washing/rinsing harvest equipment food contact surfaces.
• There are several ways in which water from the on-farm water reservoir may have come into contact with the implicated romaine lettuce, including direct harvest/postharvest application to the crop and/or use of reservoir agricultural water on harvest equipment food contact surfaces.
• FDA does not know how and when the on-farm water reservoir became contaminated with the outbreak strain. No evidence was found to identify and confirm an obvious route for on-farm contamination, or from adjacent land, to the on-farm water reservoir. Other explanations regarding how the on-farm water reservoir was contaminated with the E. coli O157: H7 outbreak strain aside from the potential contributing factors identified in this report are possible.
• Foodborne illness outbreaks caused by this specific strain of E. coli O157: H7 occurred in 2016, 2017, and 2018, indicating that the outbreak strain may have either persisted in the environment or may be repeatedly introduced into the environment from an unknown source. Public health officials in the U.S. and Canada were unable to definitively confirm the food vehicle and ultimate source(s) of the 2016 and 2017 illnesses.
• FDA cannot rule out that other sources or means of romaine lettuce contamination with the outbreak strain of E. coli O157: H7 may have occurred.

Reaction to the new report included a joint statement from Michael Taylor and Lauren Bush, Co-Chairs of the Stop Foodborne Illness Board.

“Stop Foodborne Illness appreciates FDA’s effort to promptly investigate the root cause of the recent outbreak of illness associated with romaine lettuce from California, as well as the agency’s issuance of advice to industry on measures that could help prevent future outbreaks,” the Taylor-Bush statement says. “This is a critical element of FDA’s public health mission, and consumers expect both FDA and industry to take every step possible as soon as possible to learn from past mistakes to prevent future illnesses.”

FDA Commissioner Gottlieb and Deputy Commissioner Yiannas said the agency acted quickly to protect consumers by issuing a public health warning ahead of Thanksgiving last year. At that time, the FDA and the federal Centers for Disease Control and Prevention in Atlanta were finding the genetic fingerprint for the most recent pathogen was similar to those recorded in an earlier 2017 outbreak of E. coli O157: H7.

The traceback investigation focused on several farms, and the FDA brass credited CDC with being able to “find one positive match to the outbreak strain of an on-farm water reservoir, used for irrigation, in Santa Maria, CA.”

“The investigation teams made numerous visits to leafy greens farms in various counties and growing regions of California identified through traceback, ” the statement from Gottlieb and Yiannas says. “The outbreak strain of E. coli O157: H7 was not detected in any other samples collected during this investigation.”

The farm with the water that was positive for O157: H7 issued a recall for romaine, red and green lettuce and cauliflower last Dec. 17 because the product might have been contaminated by the use of the water from an on-farm reservoir.

“As part of our investigation, we determined that the farm had a procedure in place to collect and test reservoir agricultural water for generic E. coli and to treat the agricultural water with a sanitizer before use,” the Gottlieb and Yiannas statement continues. “However, the investigation team noted the verification procedure records did not document that sufficient sanitizer was present to adequately reduce any pathogens present in the water when this water was used for direct contact with romaine lettuce at harvest, during postharvest handling, and to wash/rinse harvest equipment food contact surfaces. It’s important to note that the farm reported that it did not use water from the reservoir for the dilution of crop protection chemicals. It also remains uncertain how the outbreak strain of E. coliO157: H7 was introduced into their on-farm water reservoir.

“The finding of the outbreak strain in the sediment of the water reservoir is significant, as studies have shown that generic E. coli can survive in sediments much longer than in the overlying water. It’s possible that the outbreak strain may have been present in the on-farm water reservoir for some months or even years before the investigation team collected the positive sample. It is also possible that the outbreak strain may have been repeatedly introduced into the reservoir from an unknown source.

“The teams did find evidence of extensive wild animal activity, including waterfowl, rodents, coyotes, etc., and animal burrows near the contaminated reservoir. This likely warrants consideration as a possible source of the human pathogen found in the on-farm water reservoir. It is another factor that we will work with the farm to address. Additionally, adjacent land use including the use of soil amendments, or for animal grazing on nearby land, may have had the potential to be contributing factors.”

The FDA brass says its important for regulators to understand how leafy greens are grown and harvested; and that buyers and shippers be able to trace products back to the source at any time in the process. Gottlieb and Yiannas said they plan to keep a “shared sense of urgency” around these efforts.

The latest outbreak was the third of its kind in about a year’s time with very little product actually recalled.