A Stanford Medical School study has concluded that the microbiome – the collective genetic material of microbes in a given environment – in a healthy human lung is far less diverse than that of a cystic fibrosis patient.

This lack of diversity is as dangerous as the presence of an individual infectious agent, according to the researchers.

Cystic fibrosis is an inherited disease causing thick mucus in the lungs and digestive tract that causes chronic lung disorders. The research in this study showed that the presence of already well-documented pathogens is not the only differentiating factor about the lungs of cystic fibrosis patients.

The researchers used sputum samples – the mucus of the lower respiratory tract – from 16 people with and nine people without cystic fibrosis to compare microbe communities.

The study, co-authored by Stanford researchers Paul Blainey, David Cornfield, Carlos Milla and Stephen Quake, was published online Wednesday morning in Science Translational Medicine.

— Alice Phillips