(CBS/AP) What caused the Listeria outbreak that so far has killed 25 and sickened scores? Government health officials are eyeing pools of water on the floor and dirty equipment at a Colorado farm's cantaloupe packing facility.
Investigators found Listeria on equipment in the Jensen Farms facility and on fruit that had been held there.
In a six-page assessment of the conditions at the farm, the FDA said Jensen Farms had recently purchased used equipment that was old, corroded, and hard to clean. In addition, the facility's floors were constructed so they were hard to clean, so pools of water potentially harboring the bacteria formed close to the packing equipment.
The equipment was bought in July, the same month the outbreak started. Previously, it had been used for a different agricultural commodity, the agency said, and the Listeria "could have been introduced as a result of past use of the equipment," according to the report.
The agency said the contamination likely happened in the packing house, but the way the cantaloupes were cooled after being picked may have contributed to Listeria growth. The farm did not use a process called "pre-cooling" that is designed to remove condensation that can promote the growth of Listeria bacteria on the cantaloupe rinds. Unlike most pathogens, Listeria grows in cool conditions.
FDA said that samples of cantaloupes in Jensen Farms' fields tested negative for Listeria, but bacteria coming off the field may have initially introduced the pathogen into the packing house, where it then spread. Listeria contamination often comes from animal feces or decaying vegetation.
Another possible source of contamination was a truck used to haul cantaloupe to a cattle operation and was parked near the packing house. Contamination could have been tracked into the house by people or equipment, the report said.
The CDC says 123 people have been sickened in the outbreak, including the 25 who died. It is the deadliest known outbreak of food-borne illness in the U.S. in more than 25 years.
The tainted fruit, which Jensen Farms recalled in mid-September, should be off store shelves by now. But the number of illnesses may grow, as the symptoms of listeriosis can take up to two months to appear.
The CDC on Tuesday confirmed a sixth death in Colorado and a second in New York. Indiana, Kansas, Louisiana, Maryland, Missouri, Nebraska, New Mexico, Oklahoma, Texas and Wyoming have also reported deaths.
People at high risk for listeriosis include older adults, pregnant women, newborns, and adults with weakened immunity. Symptoms include fever, chills, muscle aches, and stiff neck. The infection can be cured with antibiotics if they're given promptly.
The CDC has more on Listeria.