Patients who have been prescribed antibiotics in hospitals are more likely to get fungal infections due to disorders of the intestinal immune system, according to a new study from the University of Birmingham and the National Institutes of Health.
Using immunosuppressive drugs in conjunction with antibiotics can reduce the health risks from these complex infections, the researchers say.
The life-threatening fungal infection invasive candidiasis is a major complication for inpatients who receive antibiotics to prevent sepsis and other bacterial infections that spread rapidly around hospitals (such as C. diff). Fungal infections can be more difficult to treat than bacterial infections, but the underlying factors that cause these infections are not well understood.
A team at the university’s institute of immunology and immunotherapy, in collaboration with researchers at the National Institutes of Health, discovered that antibiotics disrupt the immune system in the intestines, which means that fungal infections were poorly controlled in that area. Unexpectedly, the team also found that where fungal infections developed, intestinal bacteria could also escape, which led to an additional risk of bacterial infection.
The study, published in Cell host and microbe, shows the potential for immune-boosting drugs, but the researchers also say that their work also highlights how antibiotics can have additional effects on our bodies that affect how we fight infections and diseases. This in turn underlines the importance of careful management of available antibiotics.
Lead author Dr Rebecca Drummond said: “We knew that antibiotics make fungal infections worse, but the discovery that bacterial concomitant infections can also develop through these interactions in the gut was surprising. These factors can add to a complicated clinical situation – and by understanding these underlying causes physicians to better treat these patients effectively. “
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 gut, rather than in the kidneys or other organs.
In another step, the team found which parts of the immune system were missing in the gut after antibiotic treatment, and then added these back to the mice using immunosuppressive drugs similar to those used in humans. They found that 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 concomitant infections can occur in humans after they have been treated with antibiotics.
“These findings demonstrate the potential consequences of using antibiotics in patients at risk of developing fungal infections,” Drummond added. “If we limit or change the way we prescribe antibiotics, we can help reduce the number of people who become very ill from these additional infections – as well as address the huge and growing problem of antibiotic resistance.”