Bacteria In The Blood Could Contribute To A Number Of Diseases

Dormant bacteria in the blood could be behind rising inflammation and impaired blood clotting 

While the blood of healthy individuals was once believed to be completely sterile, new research is revealing a dormant burden of bacteria that can be activated under certain conditions - with a range of consequences from inflammation to clotting. A range of diseases are linked to inflammation, including Alzheimer's, diabetes and arthritis. Many age-related diseases are also linked to abnormal protein folding and clotting behaviour; something which could also be connected to these blood borne bacteria. 

A hidden burden

There have been a number of studies suggesting that Alzheimer's could arise as a response to infection and inflammation, and researchers have been testing whether they could play a role in other conditions too. It was recently established that each millilitre of blood contains on average 1000 bacterial cells; challenging the mantra that blood was sterile. These appear to be largely dormant, but for a number of reasons including raised iron levels (and perhaps a depleted immune system), they can become active and secrete lipopolysaccharides (LPS). These are molecules presented on the bacterial cell wall that trigger an immune response. 

A catalyst

These LPS molecules are bad news. Scientists studying its effects discovered that LPS molecules derived from E. coli interact with fibrinogen, which is an important molecule involved with initiating clots. LPS appeared to alter fibrinogen, causing it to form abnormal clots resembling those formed in deep vein thrombosis and strokes. Just one molecule of LPS in 100 million fibrinogen molecules appeared sufficient to initiate a misfolding cascade, acting in a similar manner to prions and causing a harmful change in fibrinogen's structure.  

Credit: Anne Weston, LRI, CRUK. Wellcome Images

“In all inflammatory conditions we have noted a matted, denser fibrin structure, without the typical ‘spaghetti structure’ found in healthy individuals” 

We know that unusual clotting behaviour is tied to inflammatory conditions, and that there may be a specific link with iron levels in the blood. Levels of iron are normally kept low in the blood, partly to limit bacterial growth. If this situation is changed with age, then bacteria may become activated and begin wreaking havoc around the body.

At the moment it's not abundantly clear exactly how much of a role these microbes play in age-related disease, but it certainly raises interesting questions. Perhaps immune decline or dysfunctional gut tissue comes first, which then allows an increased microbial presence and in turn drives inflammation. It could also be a toxic cycle, in which increasing bacterial presence contributes to immune stress - raising systemic inflammation and causing widespread issues.

Read more at The New Scientist