Hospital germs Staphylococci prefer blood

Hospital germs: bacteria in the blood

Hospital germs: According to a scientific study, staphylococci prefer human blood.
Every year, thousands of patients are infected with germs during hospital stays in Germany, 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 common in hospitals in particular. The iron needed to propagate the bacteria in an infection from the red blood cells of the host. The pathogens seem to have specialized in human hemoglobin, US scientists report in the latest issue of the medical journal „Cell Host & Microbe“.

Staphylococcus specialized in human hemoglobin
Staphylococci, like many other bacterial species, require iron to multiply. The bacteria will cover their steady iron needs in an infection from the iron-containing blood pigment hemoglobin, but the iron is packed relatively well to protect against such bacterial attacks in the red blood cells. To achieve iron anyway, Staphylococcus aureus has specific cell-binding proteins, according to Gleb Pishchany of Vanderbilt University Medical School, Nashville, Tennessee, USA, as part of their recent release. The receptors of staphylococci are specifically adapted to the molecular structure of human hemoglobin - only in an emergency, the pathogen to animal blood, according to the statement of 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 onto hemoglobin with its special binding molecule. Subsequently, the iron-containing nucleus of the red blood cells is extracted and decomposed in order to use the iron for propagation. Their research has shown that Staphylococcus aureus can use human hemoglobin more efficiently as an iron source for reproduction than the blood of mice, the US scientists write in their article. Thus, staphylococci kept in a nutrient solution had grown much slower, when the iron in the solution was available only from mouse hemoglobin and not from human hemoglobin, the researchers report. The final evidence was obtained in the study 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, said the microbiologists in their recent publication. In addition, the infection in the mice with gene defect was usually much worse and have spread to the whole body faster, the US scientists continue.

Development of inhibitors conceivable
From their findings, suggest that even smaller differences in the molecular structure of hemoglobin for the different individual susceptibility of humans to staphylococcal infections could be crucial, said the US researchers. „Why do some people become more likely to be infected with staphylococci or suffer from severe staphylococcal infections while others are not? Contributing factors could be differences in hemoglobin“, so the conclusion of the microbiologist Eric Skaar of Vanderbilt University. If this assumption is confirmed, the US scientists believe that a test could be developed that predicts a person's risk of staph infection. In addition, the development of inhibitors is conceivable, which block the docking of Staphylococcus aureus in hemoglobin and thus prevent the spread of infection, said Gleb Pishchany. Since the utilization of hemoglobin is a prerequisite for the germs can infect an organism, a Staphylococcal infection using inhibitors to block the hemoglobin receptors may possibly completely avoid, so the statement of the US scientists.

Block the hemoglobin receptors in multidrug-resistant bacteria
Since the number of multidrug-resistant bacteria Staphylococcus strains (MRSA) has greatly increased in recent years, such an inhibitor to prevent staphylococcal infection would be particularly desirable in the view of the researchers. Because with the multidrug-resistant pathogens, the classic treatment with antibiotics does not work. The bacteria have developed resistance to the drug due to the overuse of antibiotics and are no longer responsive to treatment. Such MRSA are relatively common in hospitals and lead to a variety of infections annually. An extrapolation from the Robert Koch Institute shows that in Germany in 2008, around 132,000 hospital patients suffered from an infection with MRSA. Blockers of hemoglobin receptors may well be suitable for multiresistant pathogens, US scientists hope. Also, vulnerable people, for example, could be better protected by hospital admission through special precautionary measures, Pishchany and colleagues said.

Staphylococci are very common
According to the researchers, although staphylococci are found in just under one third of all people on the nasal mucosa, only if the bacteria can penetrate the body, there is a risk of infection. However, if Staphylococcus aureus is given the opportunity to spread through favorable conditions or a weak immune system, life-threatening conditions such as pneumonia, inflammation of the heart lining (endocarditis), sepsis or Toxic Shock Syndrome (TSS) can in the worst case be triggered. With its specialization in human blood as an iron source, Staphylococcus aureus is not alone. Other bacterial species, such as the diphtheria pathogen Corynebacterium diphtheriae, prefer the human variant of hemoglobin, said the US researchers. The more medicine knew about the path of germs into the body, the easier it was to develop strategies for prevention and new therapeutic approaches, emphasized the US scientists. (Fp)

Also read:
Risk of infection in the hospital
Resistant bacteria in German hospitals

Picture: Gerd Altmann