Some consumer watchdog groups and blogs were quick to point out close-by CAFOs (concentrated animal feeding operations) were responsible for the Listeria contamination either through runoff or other means of transport (e.g., using waste as fertilizer). The animal population, according to Food and Water Watch’s 2007 numbers, in
Listeria monocytogenes are not the first bacteria that come to mind if a contamination is due to animal causes, said Dana Johnson in an FE interview. Johnson is brewery and produce specialist at Birko Corp., a
While FDA did not rule out that Listeria may have originated from the fields, its mode of entry to the packing plant was not on the cantaloupes, according to Johnson. Johnson recommends foaming entryways to any packing facility or food plant because very low residual levels of Listeria can be found most anywhere in the world on the ground, and they can enter a facility on workers’ shoes. Johnson’s company has many years of experience in the protein industry, and he thinks a multiple hurdle approach to pathogen reduction should be followed in the produce industry just as it is in the meat industry.
Once Listeria monocytogenes bacteria enter a cool, damp environment, they thrive and don’t have a lot of competition from other bacteria that prefer warmer temperatures to multiply, says Johnson. Another potential mode of entry, according to FDA, was a truck used to transport culled cantaloupes to livestock farms where the melons were used for feed.
In an exclusive FE interview, Mary Root,
On September 10, 2011, FDA and
Certain aspects of the packing facility, including the location of a refrigeration unit drain line, allowed water to pool on the floor in areas adjacent to packing facility equipment, according to FDA. Wet environments are known to be potential reservoirs for Listeria, and the pooling of water in close proximity to packing equipment, including conveyors, may have extended and spread the pathogen to food contact surfaces.
Of the 39 environmental samples collected from within the facility, 13 tested positive for Listeria with pulsed-field gel electrophoresis (PFGE) pattern combinations that were indistinguishable from three of the four outbreak strains collected from affected patients, according to FDA. Cantaloupes collected from the producer’s cold storage during the inspection were also confirmed positive for Listeria with PFGE pattern combinations indistinguishable from two of the four outbreak strains.
As a result of the isolation of three of the four outbreak strains of Listeria monocytogenes in the environment of the packing facility and whole cantaloupes collected from cold storage, and the fact this is the first documented Listeriosis outbreak associated with fresh, whole cantaloupes in the US, FDA is making several recommendations for good practices. Producers should: