Antibiotics may be responsible for soaring asthma rates

ANTIBIOTICS may be responsible for surging rates of asthma, researchers said yesterday.

Researchers believe the way the drugs interfere with gut microbes affects the immune system in the lungs.

They say their findings, based on mice experiments, could explain why the number of people suffering from asthma has soared alongside the increasing use of antibiotics. Dr Gary Huffnagle, from the University of Michigan Medical School in the US, said: “Antibiotics knock out bacteria in the gut, allowing fungi to take over temporarily until the bacteria grow back after the antibiotics are stopped.

“Our research indicates that altering intestinal microflora this way can lead to changes in the entire immune system, which may produce symptoms elsewhere in the body.” The immune system normally prevents excessive inflammatory reactions to inhaled allergens, such as pollen and pet fur.

This is achieved via immune cells called regulatory T cells, which are produced in the gut in response to swallowed allergens.

Dr Huffnagle’s team believes fungi in the gut secrete molecules that block the generation of regulatory T cells. The result is a hyperactive immune response, which can produce allergy symptoms and asthma. To test the theory, the researchers gave a five-day course of antibiotics to laboratory mice to weaken naturally occurring bacteria in their gut. The mice were then given the yeast fungus Candida albicans to create a fungal colony in their stomachs and intestines. Two days after stopping the antibiotics, they were exposed to a common mould allergen by introducing spores into their nasal cavities. Mice treated with antibiotics and colonised with the yeast showed much greater lung sensitivity to mould than those not treated.

“After antibiotics changed the mix of microbes in the GI (gastrointestinal) tract, the mice developed an allergic response in the lungs when exposed to common mould spores,” said Dr Huffnagle. “Mice that didn’t receive the antibiotics were able to fight off the mould spores.”

The findings were presented yesterday at the annual meeting of the American Society for Microbiology in New Orleans.

Dr Huffnagle said research had shown that diet also affects the balance of gut flora. Antioxidants called polyphenols, found in fruits and vegetables, could limit fungal growth while a diet high in saturated fats and sugars slowed the recovery of normal gut microbes.

“The Mediterranean diet is rich in sources of polyphenols, so it’s intriguing that Mediterranean-diet countries have lower rates of allergies, asthma and other inflammatory diseases than Western-diet countries like the US, Canada and England,” he said.

He said it was important for anyone treated with antibiotics to eat a healthy low-sugar diet, including plentiful raw fruits and vegetables, to restore the normal mix of gut microbes.

“The old saying an apple a day keeps the doctor away may be more true than we thought,” he said.