#6 Did You Know “Listeria Food Poisoning”?
Professor Emeritus at Hokkaido University
Advisor at Japan Food Research Laboratories
According to a news report from Denmark, a food-poisoning case has killed at least 12 people. Its causative food was a pork product called pancetta (Note1), and the causative substance was a microorganism named Listeria monocytogenes. Ministry of the Interior and Health of Denmark has confirmed that 20 people have displayed listerial symptoms since September 2013, and 15 of them experienced symptoms after June 2014. Among them, 12 people have died.
In the United States, 2011, a Listeria food poisoning, whose causative food was cantaloupe, killed 33 people. In Japan, no case caused by this microorganism has been reported in the food-poisoning statistics. However, a group health problem presumably caused by eating Listeria-contaminated natural cheese has been reported to the Ministry of Health, Labour and Welfare (Note2). In the West, a lot of mass Listeria food-poisoning cases have been reported. Estimated 2500 people suffer from serious Listeriosis in the United States every year, and 500 of them lose their lives.
A group health problem caused by coleslaw in Canada, 1981, was the first case in which food was scientifically determined as the source of Listeria infection. In the aftermath, a number of Listeria food-poisoning cases have been reported and their source of infection is as diverse as meat, milk, natural cheese, salad, smoked salmon, and so forth.
1) Features of Listeria
This microorganism is widely distributed in nature. It is a zoonotic disease agent and transmitted to human usually through food. Its growth temperature range is as wide as 0 to 45°C and it can multiply even in a refrigerator as shown in Figure2. It is halotolerant and can grow even in saline solutions of 10%. As it is non-sporulating, thermal killing is one of the effective countermeasures.
At the early phase of infection, flu-like symptoms rather than acute gastroenteritis are displayed. Symptoms such as fever ranging from 38 to 39 °C, headache, and vomiting appear, but healthy adults often does not experience any symptom at this phase. If it becomes severe after a long incubation period of averaging 3 weeks, it causes meningitis and septicemia sometimes accompanied by disturbed consciousness and/or spasm. Mortality rate after aggravation is about 20%. In case of fetus septicemia, Listeria is transmitted vertically from a pregnant woman to her baby in the womb, which can cause miscarriage or premature birth. Cardinal symptoms for pregnant women are fever, chill and back pain, and babies die postnatally in some cases. Pregnant women, infants, the elderly and people with disease should pay particular attention.
3) Prevention of food poisoning
Listeria exists in Japan and has been detected from various foods. We should take care to handle food in a hygienic way by practicing the instructions below.
(1) Handle food in a hygienic way.
(2) As Listeria is killed by heating, heat raw meats (such as beef, pork, chicken, and turkey) well.
(3) Wash fresh vegetables well before eating.
(4) Avoid contact of raw meats with vegetables or cooked foods.
(5) Do not use dishes that have been used for raw meats for other foods without washing or sterilizing.
(6) Wash hands, knives, cutting boards, and containers well after handling raw ingredients.
(7) Do not keep foods (either cooked or uncooked) which will not be reheated before eating in a refrigerator for a long time.
(8) High-risk people including pregnant women should avoid natural cheese made from unpasteurized milk. They are also recommended to reheat cooked meat products before eating.
(9) As shown in Figure2, Listeria is capable of proliferating, though slowly, even in a refrigerator. We should use refrigerators wisely without placing too much trust in them. WHO, World Health Organization, has issued a recommendation saying foods should not be left in the dangerous temperature zone of 5 to 60°C (see Figure3). Please focus attention on the fact that the lower limit of the danger zone is as low as 5°C.
5) Investigation on Listeria
In Japan, no Listeria-caused food poisoning has been described in an administrative report yet. However, according to the investigations by a science study group of the Health, Labour and Welfare Ministry represented by Dr. Igimi, Listeriosis patients has been identified around Japan (causal relationship with food has not been confirmed). It is estimated that annually-averaged 83 cases of severe Listeriosis occur, which is almost the same frequency as in Western countries. In consideration of the research results on Listerial food contamination in Japan, we can’t deny the possibility that Listeria food poisoning may occur in Japan someday. We should keep our eyes on this type of food poisoning as well.
Note1: http://www.europapress.es/internacional/noticia-encuentran-fuente-brote-listeria- matado-12-personas-dinamarca-20140812203605.html
References (all in Japanese)
BBC, Denmark links 12 listeria deaths to pork sausage Rullepoelse - file pic Rolled pork sausages are under suspicion in the outbreak,
delivered on August 12, 2014
Igimi, S. 2004. Health and Labour Sciences Research Grant (Food Safety Research Project). “Research on Health Problems Caused by Food-Borne Listeria.” Summary and Assigned Research Report 2003. (Note2)
Food Safety Commission of Japan. 2013. “Listeria Monocytogenes in Food.”