We explain how to avoid Listeria and how to know if you are at risk of infection.
In this article we explain everything about listeriosis, a disease with origin in the bacteriumListeria monocytogenes, a dangerous intracellular parasite, whose infection most often affects vulnerable groups, such as pregnant women and the population over 55 years.
Symptoms of Listeriosis
We could say that, in general, listeriosis occurs in two sequential clinical manifestations. During the “first phase” -which is usually the last-, the infection causes symptoms similar to those of an intestinal flu, with stomach pain, diarrhea, fever, joint pain, headache, etc. Typically, our immune system takes care of the infection before it progresses beyond the intestine.
In cases where the infection progresses, the “second phase” goes beyond the intestine, and the diseaseincreases in severity and dangerousness. This occurs more commonly in vulnerable groups, such as:
- Immunosuppressed people
- People with liver ailments (cirrhosis, alcoholism)
- People over 55 years old
- Pregnant women
- Developing fetuses
- Cancer patients
Among these groups, the diseasecauses symptoms that can be very varied. Once listeriosis has passed through the intestinal wall, which is known as invasive listeriosis, the severity of the infection depends mainly on the strength of our immune system. In general, the symptoms caused by this type of listeriosis, depending on the affected population, are:
1. In pregnant women
Symptoms in pregnant women are usually relatively mild for the mother, although pregnant womenaccount for 1 in 6 cases of listeriosis and are 10 times more likelyto contract the disease compared to other groups. You may notice flu-like symptoms, including headache, chills, joint pain, or fatigue. These symptoms are very easy to confuse with a viral flu.
Following the appearance of these symptoms, Listeria can invade the fetus through the placenta, causing miscarriages in fetuses, even those late in development . This miscarriage or death of the fetus occurs between 2 and 14 days after the onset of the symptoms described above.
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2. In non-pregnant adults
Non – pregnant adults will have very different symptoms , depending on the state of their immune system. Invasive listeriosis can lead to meningitis, severe changes in consciousness, movement disorders, and even paralysis of some nerves.
Since Listeria can invade many organs and tissues, they can cause infections of the liver, heart or lungs, for example. In addition, there is the risk of a blood infection, septicemia, quite serious.
3. Neonates
Neonates can contract listeriosis through the mother , mainly. Listeria, in addition to causing abortions and deaths of developing babies, is one of the main causes of meningitis in newborn babies.
Listeria, the culprit bacteria
Listeria Monocytogenesis an opportunistic pathogen, which has a relatively low infection rate. It exists ubiquitously in the natural environment, being found mainly in the earth and soil. It is capable of infecting livestock, such as ruminants, which can become asymptomatic carriers of the disease, which contaminate the soil with manure, in addition to posing a food risk.
We can find Listeria in fruits and vegetables that come from contaminated soils, as well as in meat and dairy products that go through an industrial process, but are consumed raw, such assome types of soft cheeses made with unpasteurized milk, or processed meats, such as sausages or shredded meat.
Listeria is an intracellular pathogen. This means that it is able to enter the cells, avoiding the action of our immune system (for example,it is able to prevent phagocytosis of macrophages). It reaches the blood through the liver, which infects after crossing the intestinal barrier. There, Listeria has the ability to infect several of our organs, especially if we have low defenses.
It is able to grow in very acidic or very salty environments, which are two of the ways we have to keep food free of bacterial pathogens. In addition, one of the most damaging characteristics of Listeria isits ability to live and reproduce in the cold of the fridge, something that few pathogenic bacteria can do.
Its high capacity to survive in conditions unviable for other pathogens, in addition to the severity of its infections in pregnant women and other vulnerable groups, make it avery great risk for the food industry, which must constantly control that the bacteria is not found in its products.
How to Prevent Listeria Infection
In 2019, Spain is currently experiencing an outbreak of Listeriosis, a priori caused by the contamination of a meat grinding machine in a factory in Andalusia.
By EU regulation, Listeria is one of the pathogens to be detected in a food analysis, and foods that contain it in even minimal quantities are considered contaminated and unfit for consumption. For this reason it is important to maintain strong microbiological control in companies that handle food and other products susceptible to biological contamination.
Listeriosis outbreaks in the developed world are often the resultof poor hygienic practices by a company, or, at best, one-off accidents committed by companies or workers of the company. The best prevention for listeriosis is high standards of health and constant surveillance at the microbiological level in companies, to avoid affecting the health of the population.
On a personal level, we can simplyavoid eating processed foods consumed raw, especially during a listeriosis epidemic. Its long incubation time makes it difficult to determine the exact magnitude of the outbreaks, so it is important that you know the possible sources of Listeria, especially if you are part of one of the groups with the highest risk of contracting it and suffering serious damage.
If you’re looking for which foods may contain Listeria, you can check out an extensive list of foods susceptible to Listeria contamination onthe CDC website. Luckily, this information is available in both Spanish and English.
References
- Vázquez-Boland, J. A., Kuhn, M., Berche, P., Chakraborty, T., Domínguez-Bernal, G., Goebel, W., … Kreft, J. (2001). Listeria pathogenesis and molecular virulence determinants. Clinical microbiology reviews, 14(3), 584–640. doi:10.1128/CMR.14.3.584-640.2001.
- Dussurget, O., Pizarro-Cerda, J., & Cossart, P. (2004). Molecular Determinants ofListeria monocytogenesVirulence. Annual Review of Microbiology, 58(1), 587–610. doi:10.1146/annurev.micro.57.030502.090934.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.
