World first discovery links gut bacteria and stroke

World first discovery links gut bacteria and stroke

Gut bacteria take advantage of a patient’s weakened immune system after stroke, and travel throughout the body causing infection, according to latest research at Monash University.

Published today in the prestigious Nature Medicine journal, the research was led by Dr Connie Wong from the Centre for Inflammatory Diseases, School of Clinical Sciences at Monash Health.

Stroke is one of Australia’s biggest killers. In addition to brain injury, infections, especially bacterial pneumonia, are common in stroke patients and often lead to death.

“We’ve known for a long time that stroke patients are highly susceptible to infections but we didn’t really understand why,” said Dr Wong.

“Our research has shown for the first time that stroke compromises the immune system, enabling bacteria to take an opportunistic journey from the gut into other organs, including the lungs.”

“We’ve shown that stroke injury can cause cellular changes which leads to barrier dysfunctions in the gut. This allows gut bacteria to spread throughout the body.”

“This is a huge concern when the gut bacteria are antibiotic-resistant, and especially when they get into other organs such as the lungs, which can lead to pneumonia and other dangerous infections.”

Dr Wong’s research explains why current treatments in fighting post-stroke infections are ineffective and provides stroke doctors with evidence that antibiotics are unhelpful.

Associate Professor Henry Ma, Head of Stroke at Monash Health, said the research has the potential to change clinical practice in managing stroke patients.

“We know that patients are susceptible to infection after a stroke, but this particular pathway for infection is not something we’d seen before. We often prescribe antibiotics for patients after a stroke but sometimes this is not effective at preventing or treating infection.”

Dr Wong said that our hugely-diverse gut bacteria outnumbers our own cells ten-to-one, and has 100 times more genes than the human genome and contains many pathogens.

“Usually our immune system keeps these gut bacteria under control. However a shock to the system, such as in a stroke, can compromise immunity, enabling bacteria to travel from the gut into organs including the lung, liver and spleen.” she said.

This discovery may change the management of stroke patients, reducing the use of unnecessary and ineffective antibiotics.

This pivotal research has been supported by the Australian Research Council (ARC), National Heart Foundation and the National Health and Medical Research Council (NHMRC).