Cantaloupe! yummy!

                You sit down for breakfast and decide you’re going to have that juicy slice of cantaloupe you have had your eye on. Little do you know that because you had that craving for some cantaloupe you will now die within 30 days. Does this sound farfetched?  Last fall that is exactly what happened to 30 people in the US. This week in infectious diseases we looked at infections of the central nervous system. In lab we received a cerebrospinal fluid (CSF) sample from a patient and we were tasked with attempting to isolate the causative organism of our patient’s symptoms. From my CSF I was able to isolate Listeria monocytogenes. This is the same bacterium that was the causative agent of an outbreak in September to October of 2011 that infected 146 persons across 28 states and led to 30 deaths and one miscarriage. The mortality rate from listeric meningitis is fairly high ranging from 20% - 80%. So if only 20% of the people that get listeric meningitis survive how do you get it? First of all not everyone exposed to the bacteria will get listeric meningitis. The infectious dose is not known but it is known that neonates, elderly, pregnant women and immunocompromised individuals are at the highest risk. People without those risk factors can be affected however it is rare. My patient was an elderly patient and this fits with meningitis since the elderly are at a higher risk for listeriosis. So you probably are thinking that you can just avoid cantaloupe and you will be ok. Listeria monocytogenes is widespread in the environment. It has been recovered from soil, water, vegetation animal products such as raw milk, cheese, poultry, and processed meats. The frequency of listeriosis according to a prospectively collected study by the CDC in 1987 showed 1600 cases of listeriosis with 415 deaths per year in the U.S. The outbreak of Listeria monocytogenes last fall was tracked back to cantaloupes from Jensen Farms in the southeast of Colorodo. This was actually the first listeriosis outbreak associated with a whole fruit or vegetable. Factors that the FDA list as possible contributing factors included:

Growing Environment:

·         Low level sporadic Listeria monocytogenes in the agricultural environment and incoming cantaloupe may have contributed to the introduction of the pathogen into the packing facility.

Packing Facility and cold Storage:

·         A truck used to haul culled cantaloupe to a cattle operation was parked adjacent to the packing facility and could have introduced contamination into the facility;

·         Facility design allowed for the pooling of water on the packing facility floor adjacent to equipment and employee walkway access to grading stations;

·         The packing facility floor was constructed in a manner that was not easily cleanable;

·         The packing equipment was not easily cleaned and sanitized;

·         The washing and drying equipment used for cantaloupe packing was previously used for postharvest handling of another raw agricultural commodity; and

·         There was no pre-cooling step to remove field heat from the cantaloupes before cold storage.

The FDA made recommendations for prevention of Listeria monocytogenes based on their findings and they included the following:

·         Assess produce facility and equipment design to ensure adequately cleanable surfaces and eliminate opportunities for introduction, growth, and spread of Listeria monocytogenes and other pathogens. 

·         Assess and minimize opportunities for introduction of Listeria monocytogenes and other pathogens in packing facilities. 

·         Implement cleaning and sanitizing procedures.

·         Verify the efficacy of cleaning and sanitizing procedures.

·         Periodically evaluate the processes and equipment used in packing facilities to assure they do not contribute to fresh produce contamination. 

 Let me know if you have additional questions. You can also find additional information about Listeria monocytogenes or the the outbreak previously discussed at: http://www.cdc.gov/listeria/