Oct 19, 2011 (CIDRAP News) – A combination of factors at Jensen Farms' packing facility most likely led to Listeria monocytogenes contamination in cantaloupes implicated in the nation's deadliest foodborne illness outbreak in two decades, the US Food and Drug Administration (FDA) said today in its investigation report.
The probe, conducted by a team of federal and state officials, found multiple problems at the Colorado packing facility, such as design flaws that led to water pooling near packing equipment and the use of equipment that was difficult to clean. The report also identified processing factors that could have promoted Listeria growth during cold storage.
Yesterday the FDA sent Jensen Farms a warning letter that detailed the findings of a Sep 10 regulatory inspection of its packing facility, which found evidence that the cantaloupe packed there were adulterated, as defined by federal law. In that inspection, 13 of 39 samples collected from the packing facility were positive for Listeria, matching three of the four outbreak strains.
Based on those findings and because the Listeria outbreak is the first involving whole cantaloupes, the FDA conducted a full environmental assessment of the company's growing fields and the packing facility on Sep 22 and 23. FDA officials, along with experts from federal and state agencies, released the findings today at a news teleconference and posted a written report on the FDA's Web site.
FDA Commissioner Margaret Hamburg, MD, told reporters that Jensen Farms has agreed to remediate the problems and have the FDA inspect the facility again before it resumes production.
Yesterday the US Centers for Disease Control and Prevention (CDC) said two more deaths have been connected to the outbreak, raising the fatality total to 25. The number of cases rose to 123, an increase of 7 since its last report on Oct 12. So far 26 states have reported cases, with the first Pennsylvania case included in the CDC's new report.
Barbara Mahon, MD, deputy chief of the CDC's enteric disease branch, told reporters that though the number of new cases has declined, it's too soon to declare the outbreak over, given the long incubation time for Listeria infections. She said the CDC will have a clearer picture in about 2 weeks.
The environmental assessment included detailed interviews with Jensen Farms managers about their food safety practices along with on-site visits to the farm, packing facility, and cold storage area.
Samples from the growing fields were negative for Listeria, but several tests from the earlier inspection of the packing facility were positive, leading the FDA to conclude that the fields, which can harbor Listeria from ruminant animals or decaying vegetation, are not a likely source of contamination. However, it added that the growing environment can't be ruled out as a possible contributor to contamination and could have allowed the pathogen to gain a foothold in Jensen Farms' packing facility and cold storage.
A truck used to haul discarded cantaloupe to a cattle operation was parked adjacent to the packing facility, which could have introduced contamination into the facility, according to the report. In response to a reporter's question, Dr Jim Gorny, senior advisor for produce safety at the FDA's Center for Food Safety and Applied Nutrition, said no sheep were grazing on the property and that according to Colorado officials, the region where the farm is located is not a significant sheep grazing area.
Sherri McGarry, senior advisor in the FDA office of foods, said none of the samples collected at the packing facility during the full environmental investigation yielded Listeria, and she noted that the facility had recently been thoroughly cleaned and sanitized.
The facility's floor, where water pooled, was not easily cleanable and could have served as a harbor for Listeria, the report said. In the earlier inspection, samples from the floor and pooled water, which may have had contact with food contact surfaces, were positive for Listeria and matched some of the outbreak strains.
In July, Jensen Farms bought and installed equipment that had previously been used at a company that produced a different crop, which McGarry identified as potatoes. The report said the equipment doesn't lend itself to easy or routine cleaning and sanitizing and that several areas appeared uncleanable, with visible dirt and product build-up on parts, even after disassembly and cleaning,. Because the equipment previously handled another type of produce that had different washing and drying requirements, Listeria could have been introduced from the equipment's past use.
Gorny said the issues surrounding the washing and drying equipment do not implicate the potato industry.
The investigators also found that the company's postharvest practices might have contributed to growth of Listeria during cold storage. Jensen Farms did not pre-cool the cantaloupe before putting it in cold storage. Not removing the field heat through hydrocooling or forced cold-air cooling can allow condensation to form on the rind, creating ideal conditions for Listeria growth. According to the report, samples from cantaloupes in cold storage collected during the inspection matched two of the four outbreak strains.
McGarry and Gorny told reporters that there is no reason to believe that the practices identified at Jensen Farms, including the facility design, equipment issues, and handling methods, are typical for the produce industry.
The FDA held a teleconference call with industry stakeholders today to review the findings and to reiterate the importance of equipment that can be easily cleaned and sanitized, verifiable food safety plans, and recognition of potential points of contamination, McGarry said, noting that those steps are the focus of the recently passed FDA Food Safety Modernization Act.
Oct 19 FDA environmental assessment of Jensen Farms
Oct 18 FDA warning letter
Oct 18 CDC Listeria outbreak update