Friends of the blog Scott Gottlieb and Frank Yiannas posted a statement to FDA’s website today detailing the findings of the agency’s investigation into over 50 E. coli O157 illnesses in the fall of 2018.

Today, we’re announcing the findings of this investigation and our best hypotheses as to how this contamination could have occurred. In the case of the one farm with a positive sample previously referenced, 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. 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.

The full report can be found here.

My favorite part is this recommendation from investigators:

Perform a root cause analysis when a foodborne pathogen is identified in the growing environment, in agricultural inputs (e.g., agricultural water or soil amendments), in raw agricultural commodities or in fresh-cut ready-to-eat produce. The goal of a root cause analysis is to determine the likely source of the contamination, if prevention measures have failed, and whether additional measures are needed to prevent a reoccurrence.

From my experience, this root cause analysis approach is hit or miss when pathogens are found during routine sampling (but maybe a barfblog reader can provide me with some details on whether they know of folks doing this).