Patients prescribed antibiotics in hospitals to prevent sepsis and other bacterial infections are at increased risk of developing a life-threatening fungal infection called candidiasis because of disruption to the immune system in the gut, a new study warned.
Gut microbiomes are generally known to carry genetically encoded strategies to survive contact with antibiotics.
But the study, led by researchers from the University of Birmingham in the UK and the US National Institutes of Health, discovered that antibiotics disrupt the immune system in the intestines, meaning that fungal infections become poorly controlled in that area.
The team also found that where fungal infections developed, gut bacteria were also able to escape, leading to the additional risk of bacterial infection.
While the study, published in Cell Host and Microbe, demonstrated the potential for immune-boosting drugs, the researchers said their work also highlights how antibiotics can have additional effects on our bodies that affect how we fight infection and disease.
This in turn underscores the importance of careful stewardship of available antibiotics.
“We knew that antibiotics make fungal infections worse, but the discovery that bacterial co-infections can also develop through these interactions in the gut was surprising. These factors can add up to a complicated clinical situation – and by understanding these underlying causes, doctors will be better able to treat these patients effectively,” said lead author Dr. Rebecca Drummond, fungal immunologist at Birmingham.
In the study, the team used mice treated with a broad-spectrum antibiotic cocktail and then infected these animals with Candida albicans, the most common fungus that causes invasive candidiasis in humans. They found that although infected mice had increased mortality, this was caused by infection in the intestine, rather than in the kidneys or other organs.
In a further step, the team pinpointed what parts of the immune system were missing from the gut after antibiotic treatment, and then added these back into the mice using immune-boosting drugs similar to those used in humans. They found this approach helped reduce the severity of the fungal infection.
The researchers followed up the experiment by studying hospital records, where they were able to show that similar co-infections might occur in humans after they have been treated with antibiotics.
An estimated 1.2 million people worldwide died in 2019 from antibiotic-resistant infections, and this number is predicted to increase ten-fold by 2050.
The new “findings demonstrate the possible consequences of using antibiotics in patients who are at risk of developing fungal infections,” said Dr. Drummond. “If we limit or change how we prescribe antibiotics we can help reduce the number of people who become very ill from these additional infections – as well as tackling the huge and growing problem of antibiotic resistance.”