The Food and Drug Administration (FDA) and California’s Department of Health Services (CDHS) recently released a joint report on the investigation into the causes of the E. coli O157:H7 outbreak last fall that was associated with contaminated Dole brand Baby Spinach. The inquiry, which was conducted by the California Food Emergency Response Team (CalFERT) and CDHS, was unable to pinpoint how the contamination originated.

The probe initially focused on the processing and packaging plant of Natural Selection Foods, LLC in San Juan Bautista, CA, where the contaminated products had been processed, then investigated the bags of contaminated spinach that had been collected nationwide from sick customers. Investigators were able to match environmental samples of E. coli O157:H7 from one field to the strain that caused the outbreak. Potential environmental risk factors at or near the field included the presence of wild pigs; the proximity of irrigation wells used to grow produce for ready-to-eat packaging; and surface waterways exposed to feces from cattle and wildlife.

However, because the contamination occurred before the investigation began, and because of the many ways in which the bacteria can be transferred, investigators were unable to determine precisely how the bacteria spread to the spinach.

The report is available at http://www.DHS.ca.gov.