Scientists find bacterial extracellular vesicles in human blood

Belgian scientists have come to the surprising finding that vesicles coming from gut bacteria, are present in blood of patients with HIV, inflammatory bowel disease and cancer. Due to the increased permeability of the intestinal wall in these patients, bacterial vesicles end up in the bloodstream and can influence the immune system. This research sheds new light into the way the gut bacteria can communicate with different organs in the human body and is published in the scientific journal Gut.

Our body lives in symbiosis with trillions of bacteria. Most of these bacteria are located in the colon and a disturbance in this intestinal flora has recently been linked to the development of diseases such as diabetes, obesity, Alzheimer's disease, inflammatory bowel disease, HIV and cancer. Gut bacteria communicate with each other, but also with human cells, using different molecules (proteins, RNA, DNA,…). These molecules can be packaged in unique small particles that are formed by bacterial cells, bacterial extracellular vesicles.

Researchers at Ghent University, led by Professor An Hendrix, have now developed a sensitive technique to detect the presence of bacterial vesicles in blood. Experiments show that patients with increased permeability of the intestinal wall show increased concentrations of bacterial vesicles in their blood. Moreover, the amount of these vesicles in the bloodstream corresponds to the extent to which the intestinal wall is damaged. Bacterial vesicles also contain endotoxins that influence the immune system and can cause inflammation in different organs. Interestingly, despite the fact that more than 100 trillion of these vesicles are present in our gut, they are not or barely measurable in blood of healthy test persons. A healthy gut barrier is apparently able to stop these vesicles in a very efficient way.