FDA Releases Findings From Romaine Lettuce Investigation
The U.S. Food and Drug Administration has made public the findings from its investigation into an outbreak last November of E. coli O157:H7 linked to romaine lettuce, for which the agency and the Centers for Disease Control and Prevention issued a public warning.
In December, the FDA revealed that it had traced the outbreak to an irrigation reservoir used by a single farm owned and operated by Adam Bros. Farms in California’s Santa Barbara County.
“In the case of the one farm with a positive sample … the FDA believes that the most likely way romaine lettuce on a specific ranch on this farm became contaminated was from the use of water from this reservoir as agricultural water,” said Commissioner Scott Gottlieb and Deputy Commissioner Frank Yiannas in a Feb. 13 statement. “It is believed that this water came into contact with the harvested portion of the romaine lettuce, since the outbreak strain of E. coli O157:H7 was found in sediment from the reservoir and in no other sampled locations. The water from the reservoir doesn’t explain how lettuce grown on other ranches or farms identified by traceback may have been contaminated. So, this one farm cannot explain the entire outbreak.”
Added Gottlieb and Yiannas: “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. 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 post-harvest 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. coli O157:H7 was introduced into their on-farm water reservoir.”
According to the officials: “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.”
Gottlieb and Yiannas noted, however, that the investigative teams discovered “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 officials also reiterated their previous recommendation that “leafy-green growers, buyer/shippers and retailers … make information about the source, such as harvest date and standardized growing regions, readily available for consumers on either packaging or point-of-sale signs, or by other means,” adding, “We believe this is the best approach to be able to inform consumers should there be any future risks to public health.”
As Gottlieb and Yiannas admitted, though, when it comes to containing outbreaks of foodborne illness, “[w]e know more needs to be done and there is a shared sense of urgency around these efforts.”
