APR 23, 2018 09:20 AM PDT

Gut Bacteria may be Causing Brain Impairment in Sepsis Patients

WRITTEN BY: Carmen Leitch

After a serious illness or surgery, some people then have to face complications in the form of body or brain dysfunction. The causes of that brain impairment have been a mystery, but scientists have started to look at a connection between these problems and gut microbes. Reporting in the American Journal of Respiratory and Critical Care Medicine, researchers have suggested that gut bacteria may be to blame for brain dysfunction in sepsis patients. 

Sepsis can lead to a variety of other health problems.

"Many will experience cognitive impairments or emotional difficulties that are equivalent to mild traumatic brain injury and can persist for months or years after their hospitalization," said lead author Benjamin Singer, M.D., Ph.D., an assistant professor of internal medicine at Michigan Medicine.

"We already know from previous studies that sepsis results in long-term brain dysfunction and that neuroinflammation plays a role in brain injury during the infection," continued Singer. "But we hypothesized that the brain injury is directly related to gut bacteria independently moving to the brain and perhaps triggering an immune response that leads to longer-term effects from the injury."
 
The relationship between the brain and sepsis had not been explored until this study, although others have suggested that sepsis might increase the risk of lung inflammation. The team used brains from deceased patients and mice to assess whether they contained gut bacteria.

"The traditional thing to do in a microbiology lab is: take a sample and try to grow bacteria from it in the lab under particular conditions and see what you get," Singer said. "We know, though, that there are many bacteria that are important in the gut microbiome but that don't grow in the traditional methods.

"We can take a sample and isolate the DNA from it and sequence the 16S rRNA gene. Then we can compare the sequences of those genes to a database of known bacteria and identify many more bacteria in the tissue, instead of relying on what grows in a culture."

Indeed, the scientists found that gut bacteria was present in mice five days after they recovered from sepsis. Those bacteria, which were gone fourteen days after the illness, have been linked to a marker of neuroinflammation, called S100A8. The same marker was found in human patients. The team also saw small differences between people who died of sepsis and those whose death had noninfectious causes.

"Anytime someone dies, bacteria grow out of control because the immune system is not keeping the bacteria in the body in check," Singer explained. "But we found that the bacteria we isolated from patients that died of sepsis were quite different from the run-of-the-mill bacteria that sit in the body after a person dies -- and did appear to be associated with neuroinflammation in the brain."

Gut bacteria can migrate to other parts of the body, where they wreak havoc. / Image credit: Pixabay

It seems that sepsis is causing gut bacteria to migrate to the brain, where it resides until a few weeks after the illness subsides; it is therefore highly likely that gut bacteria are related to the brain disorder seen in sepsis patients.

"The larger question raised by this study is: Is there anything we can do to intervene and change the consequences of critical illness for survivors?" Singer noted. "Results from the microbiome and lung inflammation study and this one suggest that one, there are bacteria that are directly involved in organ injury, and two, the bacteria that have disseminated to different organs during sepsis are not always the bacteria that the clinical laboratory identifies in the blood culture and that are the target of your antibiotic treatment."

This work may impact patient care and could influence future studies that assess whether gut bacteria might be useful in the clinic as a brain therapeutic.

"Giving patients oral antibiotics to remove those bacteria in the gut may potentially reduce long-term effects of critical illness," Singer concluded.


Sources: AAAS/Eurekalert! Via Michigan Medicine, American Journal of Respiratory and Critical Care Medicine

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
NOV 21, 2019
Microbiology
NOV 21, 2019
Salmonella Becomes More Deadly and Drug-Resistant in Central Africa
An international team of scientists has identified strains of extensively drug-resistant Salmonella typhimurium....
NOV 21, 2019
Health & Medicine
NOV 21, 2019
Effectiveness of Different Hand-Drying Methods on Reducing Bacteria on Washed Hands
Hand hygiene is vital to prevent the spread of infectious organisms, especially in healthcare settings. It is well-documented in the literature about the i...
NOV 21, 2019
Clinical & Molecular DX
NOV 21, 2019
Meningitis and Encephalitis: Testing & Diagnosis Strategies for Effective Treatment
Meningitis is an inflammation of the membranes surrounding the brain (meninges) and spinal cord. Encephalitis, on the other hand, refers to inflammation of...
NOV 21, 2019
Microbiology
NOV 21, 2019
Probiotics Linked to Bloodstream Infections in ICU Patients
Probiotics, which are live microbes, are intended to improve human health, and they are sometimes given to intensive care unit patients of all ages....
NOV 21, 2019
Microbiology
NOV 21, 2019
How a Virus Can Help Treat Alcoholic Liver Disease
Viruses don't only infect humans, some, called bacteriophages or phages, infect bacteria. Image credit: Wikimedia Commons/AFADadcADSasd...
NOV 21, 2019
Microbiology
NOV 21, 2019
Flesh-Eating Infection Turns Deadly When Two Microbes Are to Blame
Some illnesses can happen because a person is infected with more than one microbial pathogen, and these pathogens can interact....
Loading Comments...