Listeriosis, an infection caused by listeria

In recent months we have heard a lot about food poisoning, especially listeria, now, are we clear what it is? Who can it affect the most? And what can we do to avoid disease caused by this bacterium?

What is listeria?

Listeria is a bacterium very resistant in the environment with great capacity to tolerate changes in temperature and that can reproduce itself in refrigeration temperatures, from 4ºC, being able to reach multiply very significantly if it has been kept for a long time at this temperature.

What is listeriosis?

Listeriosis is the infection that causes listeria, It's about a foodborne health problemIt's relatively rare but can be serious, especially in people at risk.

Incubation period

The time that passes from when we consume the food until the first symptoms of infection appear can be very long, between one and 90 days, which significantly hinders the identification of the food causing the disease.

Symptoms

In most of the population, listeria can cause a mild picture of fever and diarrhea. However, in people who are more sensitive, these symptoms can be aggravated, if this happens the best thing to do is. Warning symptoms range from headache, the fever and the muscle pains, to the neck stiffness, the confusion, the loss of balance, and seizures.

Risk foods

Foods with higher risk to transmit listeriosis generally those who without a pre-heat treatment, we are talking about:

• Raw milk: directly milked from cow, sheep or goat, without having undergone a heat treatment (pasteurization, boiling, etc.) Here you can link to the content that is this month about foods that should not be eaten raw
• Soft cheeses: we call them that, but in reality we are referring to cheeses made with unpasteurized milk. Its appearance may be more or less soft but the milk that has been used has not undergone a pasteurization treatment. We can always request this information in the store or restaurant establishment.
• Raw sprouts: these are products that are generally consumed without a previous heat treatment, therefore, in the presence of Listeria they can cause a poisoning.
• Meat and derivatives: these foods pose a risk because they are consumed without being cooked, since they are sold directly rolled or chopped, such as cold cuts, carpaccios. The fact of having a larger contact surface makes them more vulnerable to the action of microorganisms.
• Smoked fish: these are foods that do not undergo a subsequent cooking treatment, if this were the case, the risk would decrease significantly.
• Fruits and vegetables: the problem is not the whole fruits and vegetables that we peel and clean just before consuming, but those that we keep already chopped for a more or less long period of time. For example, salads already cut, fruits prepared in Macedonian, or any fruit or chopped vegetables that will not be cooked before consuming it.
• Raw vegetablesVegetables may be contaminated at the time of harvest since listeria is present in the soil. Thus, prior to consuming a salad or any raw vegetable preparation, we must thoroughly clean the vegetables and in the case of immunosuppressed people it is highly recommended to disinfect them as well.
• Leftover food: the risk of this type of food is that we keep it in the refrigerator for a long time, especially if the temperature in the refrigerator is higher than 4ºC, and that afterwards we do not reheat sufficiently to eliminate the possible Listeria that has grown in it weather.

What can we avoid listeriosis?

As we have commented, the most worrying thing is that people considered to be more likely to suffer a serious affectation by listeriosis consume potentially risky foods. Recommendations for avoid a serious problem of listeriosis are the following:

• Know the foods with greater risk, and avoid its consumption or consume them after a heat treatment that exceeds 70ºC.
• Do not consume raw milk, that is, unpasteurized.
• Do not consume cheeses made with raw milk. To verify that a cheese is made with pasteurized milk we have to check the label or ask the seller or the person in charge of the restaurant establishment.
• Intensive heating of food that have been left over and we have kept refrigerated, taking into account that they must reach a minimum temperature of 70ºC. If you are at risk of suffering serious meanings from listeriosis, it is not recommended that you consume leftover food that cannot be well reheated, for example, salads, cold sauces, etc.
• Avoid cold cuts, sliced ​​meat products, chilled patés, smoked fish, deli meats, sausages or hot dogs. They can be consumed if we cook them or heat them to more than 70ºC. One way to check this is by visualizing how steam comes out when you reheat them.
• Must always respect the expiration dates of foods that are kept refrigerated.
• The refrigerator should always be kept at a temperature equal to or preferably less than 4ºC.
• Leftover food should be keep refrigerated as soon as possible. A maximum of two hours should pass between its preparation and storage in the refrigerator. Inside the fridge we will keep them in containers with lids and we will consume them before two or three days have passed, if we have to keep them for longer, the choice is going to be.
• Vegetables that are to be consumed raw in hygienic conditions just before consuming them. Vegetables that are to be eaten raw should be washed well and it is recommended that those most at risk disinfect them. To disinfect them we must treat them prior to consumption with a hypochlorite solution for five minutes in the amounts indicated according to the manufacturer.
• Always keep the maximum hygiene of utensils kitchen surfaces, as well as hands, complying with the four fundamental rules of food safety: clean, separate, cook and cool.

People at higher risk

They are those that have their weakened immune system due to different causes. The main risk groups are:

• Newly born: The foods that we are going to offer to a baby should always be those with the lowest risk and the lowest bacterial load, since they do not have a fully developed immune system.
• People over 65 years of age: As we get older our immune system is diminished. In older people we must take extreme food hygiene conditions by cleaning well all those foods that we are going to consume raw, keeping them in the refrigerator for a short time, never leaving them at room temperature and cooking completely those that are cooked.
• Pregnant women: During pregnancy, the body is subjected to a situation of stress, the immune system of one is not at its best and therefore we must take extreme hygiene measures. In addition, in the case of listeria we must take into account that it is capable of crossing the placental barrier and affecting the fetus, causing serious consequences.
• Immunosuppressed people: We refer to people whose health has a compromised immune system (people undergoing chemotherapy, or who have received a transplant, cancer, diabetes, acquired immunodeficiency syndrome (AIDS), kidney or liver disease) .

• Listeria is a bacterium very resistant to changes in temperature and that they can reproduce in refrigeration temperatures between 4 and 6 degrees.
• Listeria infection is especially serious in people with a compromised immune system pregnant women, newborns, elderly and / or sick people.
• The food Raw milk and cheeses made with unpasteurized milk, smoked fish, deli meats, raw sprouts, raw fruits and vegetables, and leftover foods are most likely to transmit a listeria infection.

Bachelor of Food Science and Technology Diploma in Human Nutrition and Dietetics