Listeriosis, caused by bacteria, especially affects pregnant women and immunosuppressed people. If it is transmitted to the developing fetus, it can cause death. We explain how to prevent it.
Listeriosis is an infection caused by infection bacteria Listeria monocytogenes that can occur in pregnant – and transmitted to the fetus in development- in babies newborns. Generally, any individual with an immune system compromised (such as the elderly, patients with AIDS, diabetics, etc.) becomes severe or difficult to control in many patients.
The listeriosis outbreak broke out in the summer of 2019 in Andalusia, which has affected at least 210 people in this community. In addition to other cases under study and pending confirmation throughout the country, the consumption of shredded meat contaminated with the bacteria above is determined by the analyses carried out at the Carlos III Health Institute in Madrid. However, from the time a person ingests Listeria until he develops the disease, it can take two to six weeks, so it is sometimes difficult to accurately identify contaminated food.
How ‘Listeria monocytogenes is transmitted
The Listeria monocytogenes are widely distributed in the environment. Fresh water and wastewater, soil and farmland, vegetation, domestic and wild animals, however, the main mechanism of transmission to humans are the ingestion of the bacteria directly through food.
Cases of listeriosis outbreaks such as the one occurring in Andalusia are always associated with the consumption of food, both raw – vegetables, fruits, unpasteurized milk, and packaged products. In most cases – (sausages, meat, cheeses, smoked products, unpasteurized products) contaminated by the bacteria in question, which can also survive in the fridge at low temperatures.
On the other hand, it should be noted that Listeria monocytogenes does not cause disease in healthy humans but only affects immunosuppressed people by mechanisms that we will explain later. We can analyze samples from a healthy person’s intestine and see that there are Listeria monocytogenes without this being any problem.
What is ‘Listeria monocytogenes like
The Listeria monocytogenes is a bacterium of Gram-positive bacilli, i.e., it is elongated and stained purple with Gram stain, and in its outside wall has lipoteichoic acids involved in the virulence of the microbe. Around its body, it has flagella that work like propellers so that bacteria can move around at room temperature.
This microorganism owes its name to Joseph Lister, a 19th-century English physician who implanted aseptic and antiseptic surgery conditions, greatly reducing mortality rates. This scientist is not the discoverer of the bacterium, although it was named Listeria in his honor.
Causes of Listeriosis
When we talk about the causes of Listeriosis, we must point to the bacterium Listeria monocytogenes, which is introduced into our body. When we ingest it through the consumption of contaminated food, such as shredded meat, People can also become infected with Listeria by consuming unwashed raw vegetables (due to contamination of the soil or the fertilizer used in their production).
By drinking unpasteurized milk or by eating processed products contaminated in their packaging or handling. ( cold cuts, hot dog sausages, soft cheeses).
In all these cases, upon reaching the intestine, the bacteria come into contact with the enterocytes (cells that line the intestine wall on the inside) and pass inside. After that, the pathogen can pass from cell to cell without ever being in the external environment.
When this happens in healthy people, it does not have a major impact because Listeria is isolated in the intestine and is not dispersed throughout the body. Still, when it happens to a person with low cellular immunity, the bacteria can evade these weakened defenses and cause infection at various levels.
Who can be affected the most by listeria infection
The most vulnerable people to get a Listeria monocytogenes infection are the following:
- Elderly (it is estimated that 50% of those affected are over 65 years of age), especially if they suffer from any pathology.
- Poorly controlled diabetics or with many years of evolution of the disease.
- Patients with solid or hematological cancer are both due to cancer itself and the chemotherapy treatment it entails.
- Sick with AIDS.
- Patients on chronic treatment with corticosteroids.
- Liver or kidney disease.
- People who have undergone an organ transplant.
All these people have in common a more or less constant and more or less intense state of immune suppression. In the section on symptoms, we explain the clinical repercussion of Listeriosis in some of them due to their particular characteristics.