Hospital germs: According to a scientific study, staphylococci prefer human blood.
Every year, thousands of patients in Germany are infected with germs during a hospital stay, often with fatal consequences for the health of those affected - deaths are not uncommon. US scientists have now carefully analyzed how one of the most common pathogens, Staphylococcus aureus, multiplies. Staphylococci (Staphylococcus aureus) are relatively widespread, especially in hospitals. The bacteria get the iron they need for reproduction from the red blood cells of the host when they become infected. The pathogens apparently specialize in human hemoglobin, US scientists report in the current issue of the medical journal "Cell Host & Microbe".
Staphylococci specializing in human hemoglobin Like many other types of bacteria, staphylococci require iron to multiply. The bacteria cover their constant need for iron when they are infected with the iron-containing blood pigment hemoglobin, but the iron is relatively well packaged in the red blood cells to protect it from such bacterial attacks. In order to get the iron anyway, Staphylococcus aureus has special binding proteins in the cell envelope, report Gleb Pishchany from Vanderbilt University Medical School in Nashville (Tennessee, USA) in the context of their current publication. The receptors of the staphylococci are specially adapted to the molecular structure of human hemoglobin - the pathogens only switch to animal blood in an emergency, according to the US scientists.
Staphylococcus extracts the iron from hemoglobin If staphylococci enter the bloodstream, the pathogen attacks the red blood cells, pierces their outer shell and docks with their special binding molecule on the hemoglobin. The iron-containing cell nucleus of the red blood cells is then extracted and decomposed so that the iron can be used for reproduction. Her research has shown that Staphylococcus aureus can use human hemoglobin more efficiently as an iron source to reproduce than the blood of mice, the US scientists write in their article. The researchers report that staphylococci that were kept in a nutrient solution grew significantly more slowly if the iron in the solution was only available from mouse hemoglobin and not from human hemoglobin. The final proof was successful in the investigation of mice that formed human hemoglobin due to a genetic modification. Because the animals were far more susceptible to invasive staphylococcal infections than genetically unchanged mice, the microbiologists said in their current publication. In addition, the infection in mice with a genetic defect was usually much worse and spread to the whole body more quickly, the US scientists continued.
The development of inhibitors conceivable based on your findings suggests that even small differences in the molecular structure of hemoglobin could be decisive for the different individual susceptibility of humans to staphylococcal infections, the US researchers explained. “Why are some people more likely to get staph or have very serious staph infections while others don't? Differences in hemoglobin could be partly responsible for this, ”concluded microbiologist Eric Skaar from Vanderbilt University. If this assumption is confirmed, the U.S. scientists believe a test could be developed that predicts a person's risk of staph infection. In addition, the development of inhibitors is conceivable that block the docking sites of Staphylococcus aureus with hemoglobin and thus prevent the infection from spreading, explained Gleb Pishchany. Since the utilization of hemoglobin is a prerequisite for the germs to be able to infect an organism, a staphylococcal infection with the help of inhibitors to block the hemoglobin receptors can possibly be completely avoided, according to the US scientists.
Blocking the Hemoglobin Receptors in Multi-Resistant Germs Since the number of multi-resistant bacteria Staphylococcus strains (MRSA) has increased significantly in recent years, such an inhibitor to avoid staphylococcal infection would be particularly desirable in the researchers' opinion. Because with the multi-resistant pathogens, the classic antibiotic treatment does not work. The bacteria have developed resistance to the active ingredient due to the overuse of antibiotics and no longer respond to the treatment. Such MRSA are relatively common, especially in hospitals, and lead to a large number of infections every year. An extrapolation from the Robert Koch Institute shows that around 132,000 hospital patients in Germany suffered from an MRSA infection in 2008. Inhibitors to block the hemoglobin receptors could well be suitable for therapy with multi-resistant infectious agents, so the hope of the US scientists. Pishchany and colleagues explained that particularly vulnerable people could be better protected, for example, when they are admitted to a hospital, through special precautionary measures.
Staphylococci are widespread According to the researchers, staphylococci can be detected on the nasal mucosa in almost a third of all people, but only if the bacteria can penetrate the body is there a risk of infection. If, however, favorable conditions or a weak immune system give Staphylococcus aureus the opportunity to spread, life-threatening illnesses such as pneumonia, inflammation of the inner skin of the heart (endocarditis), blood poisoning (sepsis) or the toxic shock syndrome (TSS) can be triggered in the worst case. With its specialization in human blood as an iron source, Staphylococcus aureus is not alone. Other types of bacteria, such as the diphtheria pathogen Corynebacterium diphtheriae, also prefer the human variant of hemoglobin, the US researchers explained. The more the medicine knows about the path of germs in the body, the easier it will be to develop prevention strategies and new therapeutic approaches, the US scientists emphasized. (fp)
Infection risk in the hospital
Resistant bacteria in German hospitals
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