Infection with salmonella, for example through contaminated food, causes an unpleasant acute inflammation of the intestine with diarrhea, headache, abdominal and joint pain, malaise and sometimes vomiting. After all, she is often not life-threatening. Those affected should drink a lot and counteract dehydration: this makes the infection dangerous in weakened people, the elderly and young children. In the medical industry, however, the typical outbreaks of the notifiable disease cause headaches, because some of the Salmonella can be treated very poorly in some patients. Despite treatment with antibiotics, they sometimes continue to excrete new pathogens long after the symptoms have subsided and can thus infect other people again.
The phenomenon of these so -called permanent outlets has been researched for a long time. It is speculated that the person's immune system plays a role and that part of the bacteria not killed by the antibiotic does not completely eliminate. However, the reasons for this were not clear, and it is also unknown who could be affected. Antibiotics are therefore only recommended for treatment in severe cases: a situation in which some bacteria can get used to antibiotics for a long time and form resistant trunks under the selection pressure of the active ingredient.
A team of researchers led by Dirk Bumann from the Biozentrum of the University of Basel has now investigated how typhoid-causing Salmonella in the body manages to avoid an antibiotic attack. This showed that salmonella in certain tissues of the body can hide more or less well from the attacks of the immune system in order to survive.
The scientists have investigated the bacteria in the body with positron emissomography (PET), whereby they first searched the spleen of infected mice for salmonella. It became clear that the vast majority of salmonella can be found in the red pulp of the spleen - the part of the inside of the spleen, which is well flowed through by the blood, in which, among other things, older red blood cells are broken down.
The salmonella in this part of the spleen is almost always completely killed by antibiotics, the researchers found. The situation is different with the few bacteria that appear in the white pulp of the spleen. The white pulp of the spleen is a heart of the lymphatic system and initiates attacks by the immune system – but the bacteria hidden in it survive antibiotic therapy well, Bumann and his team write in the journal PNAS.
Apparently, the coordinated attack of antibiotics and the immune system on the bacteria is working poorly, especially in the white part of the spleen, the researchers further determined. The decisive factor here are neutrophilic white blood cells, which can only be found in very small quantities in the white pulp – unlike in the red pulp – a few days after an infection and the start of antibiotic therapy. The germs that persist there can then always send new bacteria to the rest of the body and make the infection acute again and again for a long time despite treatment.
The researchers hope that a possible way out could be to boost body defense, for example with the help of immunotherapy: This could effectively increase the density of neutrophils in the white pulp of the spleen and make the treatment of patients more efficient.
