Monash discovery links gut bacteria and stroke

Dr Connie Wong

Monash University research has found that gut bacteria are the culprit in deadly post-stroke infections such as pneumonia, heralding a new approach to stroke patient management.

Stroke is one of Australia’s biggest killers affecting one in six people, with the condition killing more women than breast cancer and more men than prostate cancer. In addition to brain injury, bacterial pneumonia infections are common in stroke patients, often leading to death.

Monash research has found gut bacteria are the major cause of post stroke infections, with bacteria able to take advantage of a stroke patient’s weakened immune system to travel through the body causing infection.

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

 Dr Wong said the research explained why current treatments in fighting post-stroke infections were ineffective and provided stroke doctors with evidence that antibiotics were unhelpful. 

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

“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 said.

Head of Stroke at Monash Health, Associate Professor Henry Ma, said the research had 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 our hugely-diverse gut bacteria outnumbered our own cells ten-to-one, and had 100 times more genes than the human genome and contained 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,” Dr Wong 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).