Professor Antonella Castagna explains everything about Listeria monocytogenes bacterium and listeriosis: symptoms, death, where it is found, treatment and incubation.
These days, the word “outbreak” is always very scary. For this reason, when the Tre Valli farm decided to withdraw some batches of its own production of sausages from the market – as some packages had been contaminated by Listeria monocytogenes – the level of attention and concern immediately increased. The cause, in fact, lies in the number of cases (66) and deaths (3) caused by this bacterium from 2020 to today. The ministry of health specified that the 3 deaths concerned particularly fragile and immunocompromised people and occurred in December 2021, March 2022 and June 2022 respectively in Lombardy, Piedmont and Emilia Romagna. But what is it exactly, and what are the risks for those who contract Listeriosis, brought precisely by this bacterium? Professor Antonella Castagna, head of the Infectious Diseases Unit of the San Raffaele Hospital in Milan, explained this to Gazzetta Active.
Professor, what is happening and why is there so much talk about Listeria Monocytogenes?
“It is a ubiquitous bacterium, present in the environment, and we can find it both in raw elements and transformed during processing. Humans are generally infected by food, ingesting the bacterium that can be present in water, milk, or vegetables, soft cheeses, smoked fish, undercooked meat or inadequately preserved after processing. Listeria monocytogenes is in fact a very resistant bacterium, more than others; it can resist refrigeration, drying and freezing. We are witnessing a series of cases that could be attributable to a specific food contamination. In July, when a boy was hospitalized for Listeria, the offending bacterium was also identified in a package of chicken frankfurters he had at home. From there, the controls were triggered that made it possible to break the chain, withdrawing from the market the packages at risk, a necessary and correct procedure. We expect this to have a major positive impact on the number of new cases ”.
What are the risks for those who contract this bacterium?
“The bacterium in question causes listeriosis, a disease that can be serious in pregnant women and immunosuppressed patients, while in other people it generally causes a gastrointestinal-febrile syndrome that resolves spontaneously and fairly quickly. In fact, we only know the number of cases severe enough to require clinical attention, but we don’t know how many people may have had listeriosis and overcome it spontaneously. Listeria can give a serious disease when it enters the blood: this happens, as mentioned, in pregnant women, especially endangering the fetus, and in immunosuppressed patients, in which a characteristic picture of meningoencephalitis can develop, in which the the bacterium is therefore able to reach the central nervous system as well ”.
“There are specific antibiotics. Listeria is resistant to cephalosporins, so we basically use two drugs in combination: ampicillin and gentamicin. As for the milder cases, as mentioned, they hardly come to the doctor’s attention. If they are not very demanding cases, patients usually treat themselves at home by dealing with gastrointestinal symptoms ”.
Can it therefore happen that the bacterium remains active even after cooking the food? What can be done to prevent it?
“It is very important, when we buy a food, to always take into consideration the expiry date and the indications given for proper conservation. It is very important to wash your hands well before cooking or handling food. It is important not to consume foods that require cooking raw: cooking foods adequately reduces the bacterial load present and therefore the possibility that the bacterium causes disease if ingested. In addition, it is important to properly preserve cooked foods, if not consumed immediately, not leaving them at room temperature but keeping them in the refrigerator and then reheating them to a suitable temperature before consumption “.