I know that sounds a tad harsh. I am sure the owners and employees of Jensen Farms, Frontera, Primus Labs and the various retailers (known and not yet known), are all nice people. Some have families and some even go to church, but the fact is their cantaloupe killed. And, to me it is pretty clear how the outbreak happened.
This morning I was reading the FDA’s “Environmental Assessment: Factors Potentially Contributing to the Contamination of Fresh Whole Cantaloupe Implicated in a Multi-State Outbreak of Listeriosis,” and the following highlights of how the outbreak happened were hard to ignore:
A. Growing Environment
All environmental samples collected in the growing fields were negative for Listeria monocytogenes… Because the samples collected in the growing fields were negative for Listeria monocytogenes whereas the environmental samples collected in the packing facility and cantaloupe collected in cold storage (discussed further below) were positive for Listeria monocytogenes,the growing fields are not a likely means of contamination.
B. Packing Facility and Cold Storage
The following factors may have contributed to the introduction, growth, or spread of Listeria monocytogenes contamination: facility and equipment design and postharvest practices.
1. Facility Design
… Certain aspects of the packing facility, including the location of a refrigeration unit drain line, allowed for water to pool on the packing facility floor in areas adjacent to packing facility equipment. Wet environments are known to be potential reservoirs for Listeria monocytogenes and the pooling of water in close proximity to packing equipment, including conveyors, may have extended and spread the pathogen to food contact surfaces. Samples collected from areas where pooled water had gathered tested positive for an outbreak strain of Listeria monocytogenes…
… Further, the packing facility floor where water pooled was directly under the packing facility equipment from which FDA collected environmental samples that tested positive for Listeria monocytogenes with PFGE pattern combinations that were indistinguishable from outbreak strains. The packing facility floor was constructed in a manner that was not easily cleanable. Specifically, the trench drain was not accessible for adequate cleaning…
… Another potential means for introduction of Listeria monocytogenes contamination into the packing facility was a truck used to haul culled cantaloupe to a cattle operation. This truck traveled to and from a cattle operation and was parked adjacent to the packing facility where contamination may have been tracked via personnel or equipment, or through other means into the packing facility…
2. Equipment Design
… The design of the packing facility equipment, including equipment used to wash and dry the cantaloupe, did not lend itself to be easily or routinely cleaned and sanitized. Several areas on both the washing and drying equipment appeared to be un-cleanable, and dirt and product buildup was visible on some areas of the equipment, even after it had been disassembled, cleaned, and sanitized. Corrosion was also visible on some parts of the equipment…
… Environmental samples collected from the packing facility equipment tested positive for Listeria monocytogenes with PFGE pattern combinations that were indistinguishable from three of the four outbreak strains…
3. Postharvest Practices
… After harvest, the cantaloupes were placed in cold storage. The cantaloupes were not pre-cooled to remove field heat before cold storage. Warm fruit with field heat potentially created conditions that would allow the formation of condensation, which is an environment ideal for Listeria monocytogenes growth…
… Samples of cantaloupe collected from refrigerated cold storage tested positive for Listeria monocytogenes with PFGE pattern combinations that were indistinguishable from two of the four outbreak strains…
And, do not forget that cantaloupe samples taken from a Denver area retailer tested positive for Listeria.
So the how the outbreak happened seems pretty clear – the packing shed did it, and shipper, auditor and retailers just wanted to sell cantaloupe.