Food safetyListeriosis outbreak causes 29 deaths, costs producer $150 million

Published 23 November 2011

Four outbreak strains of L. monocytogenes, the bacterium that causes listeriosis, were found in twenty-six states, leading to twenty-nine deaths and thirty-three additional illnesses; settlements to the families may cost $150 million; an investigation by the FDA and CDC identify a Colorado cantaloupe producer as the source of the outbreak

The bacterium that causes listeriosis, L. monocytogenes, produces different symptoms depending on a person’s risk factors. Listeriosis normally starts with diarrhea followed by fever and muscle aches, similar to the symptoms of flu. If pregnant women develop the flu-like symptoms they may also endure complications including miscarriage, stillbirth, premature delivery, or a fatal infection of the newborn infant. Elderly people with defective immune systems and young children can develop headaches, stiff neck, mental confusion, loss of balance and convulsions, and can result in fatal meningitis or encephalitis. The onset of symptoms can occur anytime between three days to two months after infection occurs.

An SGS release reports that the Colorado Department of Public Health and Environment reported it had nine cases of listeriosis including two deaths on 2 September 2011 prompting the U.S. Food and Drug Administration (FDA) and U.S. Centers for Disease Control and Prevention (CDC) to launch an urgent investigation of the multiple state outbreak in which cantaloupe was the suspected infection vehicle.

On 10 September 2011 the FDA and Colorado state officials visited cantaloupe producer Jensen Farms to collect multiple samples. Of the thirty swabs taken, thirteen were confirmed positive for L. monocytogenes with pulsed-field gel electrophoresis (PFGE) pattern combinations matching three of the four outbreak strains. In addition, cantaloupes from the firm’s cold storage area confirmed positive for the bacteria with PFGE pattern combinations matching two of the four outbreak strains.

The FDA identified several factors that most likely caused the introduction, spread, and growth of L. monocytogenes at Jensen Farms. The problem may have stemmed from bacteria in the field where the cantaloupes were grown or through contamination of the packing facility by a truck that hauled reject cantaloupes to a cattle operation. The bacteria may also have spread in water near the machinery and employee walkways, hard-to-clean floors or machinery in the packing facility, or from equipment previously used for other agricultural products. Bacteria growth is likely promoted by condensation, due to a missing pre-cooling step prior to cold storage.

The FDA concluded that if the facility had followed the non-binding recommendations for minimizing microbial food safety hazards in melons, as published by the FDA in July 2009, these problems might have been avoided.

Obligatory standards will soon be enforced under the Food Safety Modernization Act of 2010, providing new authorities for the FDA.

The release notes that in all, four outbreak strains of L. monocytogenes were found in twenty-six states, leading to twenty-nine deaths and thirty-three additional illnesses. Settlements to the families may cost $150 million.