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Some of the deadliest bacteria react to human blood and are directed to it, because its serum contains substances that serve as food for them. American scientists talked about this phenomenon, which was called "bacterial vampirism".
Washington State University graduate student and one of the authors of the study Sienna Glenn under the microscope / © Washington State University, Ted S. Warren
A recent study published in the journal eLife, gives a new insight into the nature of bloodstream infections. Having better understood it, doctors will be able to offer more effective methods of treatment.
The Enterobacteriaceae family of bacteria includes both representatives of the normal microflora of the human body and a large number of pathogens, including salmonella and Escherichia coli.
Some of the enterobacteria are associated with gastrointestinal bleeding and bacteremia, and are considered the leading cause of death from sepsis in people with inflammatory bowel disease. However, the behavior of these microorganisms and the mechanisms that encourage them to enter the bloodstream have not been sufficiently studied. A team of specialists from the University of Washington State and the University of Oregon (both in the USA) undertook to fill the gap.
Researchers have established that blood serum attracts at least three types of pathogenic bacteria - Salmonella enterica, Escherichia coli і Citrobacter koseri. One of the attractive substances for them turned out to be the amino acid L-serine present in the blood, which is involved in the construction of almost all natural proteins. By the way, it is often included in protein shakes.
Using an experimental setup called Chemosensory Injection Rig Assay (CIRA), developed by one of the authors, researchers simulated intestinal bleeding outside a living organism and, with the help of a powerful microscope, observed in real time the reaction of pathogens to tiny injections of blood serum. It took the bacteria less than a minute to find the “food source”.
In addition, as part of the study, it was found that bacteria Salmonella there is a special protein receptor tr, which enables them to "hear" the blood serum and direct to it. Using the method of protein crystallography, scientists were able to see how chemoreceptor atoms bind to L-serine. It is as a result of this mechanism that bacteria recognize the amino acid and then absorb it.
Having compiled a map of the phylogenetic distribution of the chemoreceptor tr, researchers found its presence not only among enterobacteria, but also in families Morganelliaceae і Yersiniaceae. This allows us to assume that other pathogenic microorganisms are able to react to blood serum.
We would like to add that inflammatory bowel diseases include Crohn's disease and ulcerative colitis - recurring diseases characterized by chronic inflammation of various parts of the gastrointestinal tract, accompanied by diarrhea and abdominal pain. They develop at any age, but more often begin before the age of 30.
Data on the prevalence of inflammatory bowel diseases in the world vary. In the USA and the countries of Western Europe, higher indicators are noted than in other countries.
