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Managing to keep meat from spoiling has been with us since the Stone Age. We have made real progress in food processing, but to what advantae is yet to be seen. Listeria is one of many bacteria found in our environment and accounts for about 1% of foodborne illnesses.
It is impossible to avoid contact with Listeria bacteria, but it can be minimized by following a few simple rules. Listeria monocytogenes is naturally found all around us in soil, sewage and animals.
There is little chance to actually eradicate it. Infections in humans are rare. Infection is called Listeriosis and usually limited to those whose immune system is depleted or busy fighting other things. Examples are cancer patients, babies, pregnant women and the elderly.
Listeria is named after a prominent 19th century surgeon, Dr. Joseph Lister, 1st Baron Lister (1827-1912), who exposed and proclaimed the notion that invisible "germs" cause disease in humans. He insisted that surgeons wash their hands with a mild acid solution used to treat sewage.
Dr. Lister also insisted on wearing gloves during surgery, and single handedly changed the infection rates in many British Hospitals. Listerine is a bacterial mouth-wash named in his honor.
Listeria bacteria have a tail or flagellum and can be sub-typed. The sub-types provide a clue to a common source of infection such as the recent Maple Leaf Foods outbreak.
If a healthy person eats a great quantity of infected meat, he or she may get acute vomiting, fever and diarrhea as with most other stomach infections. In some people, Listeriosis is able to flourish in a latent or unnoticeable stage, and re-emerge weeks later as a more serious infection involving the brain and blood. It does this with a protein on its surface called Internalin B, which causes some cells of the intestine to allow the bacteria to enter and be shielded from patrolling immune destroyer cells.
For some reason, using antacids promotes this process. Listeriosis is a difficult infection to spot and track down. The acute infection usually involves diarrhea, but in the latent phase, this valuable symptom is long gone.
Unexplained fevers, joint aches, muscle pains and fatigue are vague clues that can have many other causes. It is not until the symptoms of brain infection, called meningitis, or blood infection, called septicemia, emerge that blood cultures and spinal taps are done to reveal the source as Listeria.
There is antibiotic treatment available, but other health factors often complicate the picture. These rare, but serious infections are difficult to survive.
The Listeria bacteria are hardy and can resist cold storage. They are susceptible to heat and pasteurization. Yearly Listeria cases number only a few dozen in our province (Ontario), but do result in several deaths. Hight risk foods include prepared ready to eat ones such as sandwich meats, paté, sushi, unpasteurized milk and honey.
Even leftovers, soft cheeses and stored salads can harbor bacteria. Thorough cooking and cleanliness is your best defence. Limiting processed meats is generally a healthy and wise choice anyway. See you on the sidewalks!