These chicken legs from DekaMarkt are best avoided. They may be contaminated with salmonella. Usually, such a contamination results in fever and vomiting, but in some cases, it can be dangerous or even fatal. What exactly is salmonella?
In the Netherlands, an estimated 30,000 people annually experience acute gastrointestinal infection due to salmonella, according to the RIVM. “Salmonella is the collective name for a group of pathogenic bacteria that occur in humans and animals,” says Jacques Neefjes, professor of chemical immunology at the Leiden University Medical Center (LUMC).
There are about fifteen hundred types of salmonella. “The two best known are Salmonella enteritidis and Salmonella typhimurium. The first variant is transmitted through chickens and cattle, so by eating contaminated raw eggs and raw meat. The second variant is transmitted by sick mice, whose excrements end up on vegetables and fruit. The chance that a human infects another human is small.”
Salmonella generally causes diarrhea and intestinal complaints. These complaints are, according to the professor, harmless and comparable to being very sick for a day from food poisoning. But there are exceptions: “This concerns a vulnerable group of people whose immune system does not work as well,” says Norbert Vaessen, medical microbiologist at the Franciscus Gasthuis & Vlietland. “Think of babies, people over fifty, people with underlying diseases, and people with vascular prostheses.”
With fatty foods, you get sick faster from fewer bacteria
In this group, only a small amount of bacteria is needed to become ill. In the worst case, the bacterium goes through the intestinal wall and then into the bloodstream, attacking the bones, liver, and even the brain. “We see this severe clinical picture especially with Salmonella typhi and Salmonella paratyphi, which mainly occur in Africa. There, salmonella is the main cause of death among babies.”
People without good stomach acid production form another risk group that is not quickly thought of, according to Vaessen. “Stomach acid destroys the bacterium,” explains the medical microbiologist. “In people who have little stomach acid, salmonella goes directly to the intestines. They also need fewer bacteria to become ill,” he continues.
“How sick you become depends on the amount of bacteria you ingest and how you ingest them. With fatty foods, you get sick faster from a small amount of bacteria, which is why a number of people became so sick from those contaminated chocolate eggs (from the brand Kinder, ed.).”
Research shows a link between salmonella and bowel cancer
Neefjes has been researching the link between salmonella and cancer for years. For example, the professor showed how salmonella can convert healthy cells into cancer in mice. Later, he conducted research in collaboration with the RIVM, the Antoni van Leeuwenhoek, and the VUmc in Amsterdam. This showed that there is a link between salmonella and bowel cancer.
People infected with Salmonella enteritidis would be three times more likely to get the disease. “Red meat increases that chance 1.2 times,” he says. “We must be careful with this outcome, because other causes always remain possible.” Comparison site Independer reports that each form of bowel cancer has a different way of treatment.
Listeria is also transmitted via food, especially via raw milk cheeses, such as brie, roquefort, gorgonzola, and camembert. “Generally, listeria causes mild flu symptoms,” says Neefjes. “In pregnant women, it can cause premature birth or miscarriage.”
Wash hands after contact with animals
Listeria, like salmonella, can be indirectly fatal for a vulnerable group. Sepsis can occur, and an infection can, in rare cases, lead to meningitis.
However, the professor adds a small caveat: “You have to realize that there are about ten times as many bacteria in and on you as you have cells yourself. Some are useful, others find us useful. But a few make us sick, and we have antibiotics for that.”
A salmonella infection can be easily prevented by heating food to above 70 degrees Celsius. “Then the salmonella bacteria die,” explains the medical microbiologist. “Also, always keep raw meat separate from other food and cut it on different cutting boards.”
“What is often forgotten is that pets can also be a source. Not only dogs and cats, but also reptiles, for example. About 1 percent of salmonella comes from reptiles. Their terrariums are often full of excrement. So always wash your hands when you have been in contact with animals.”