Portrait of a Mystery: The Bacteria/Asthma Connection
January 7, 2011 
In my last post, I discussed some of the intriguing association between lung and gut bacteria, and asthma. The richer and more varied the bacterial community in a child’s respiratory and digestive system, the less likely that child is to suffer from asthma.
In experiments with mice, one researcher found that many courses of antibiotics seemed to make baby mice more likely to have asthma. This makes sense, for the antibiotics would diminish the presence of many species of bacteria living inside the mice.
This same association between antibiotics and asthma seems to be true of human children.
But about ten years ago, a study led by Dr Maija Leinonen showed that a possible cause of asthma in humans was infection by the bacterium Chlamydia pneumoniae. Leinonen thought a protein produced by this bacterium might sensitize patients’ immune systems and make them over-reactive to normally benign substances like dust or pet dander. She found that a course of antibiotics given to people who had suffered infection by C. pneumoniae alleviated asthma.
Around the same time, however, Stephen Holgate created a vaccine with dead soil bacteria, and found that this vaccine alleviated asthma symptoms in 67% of the members of a small study.
These are only two instances of confusing results of asthma studies. Yet notice that one of the wonders in all this material is the apparent connection between microbes in our bodies and asthma.