ABCs of the lung microbiome.

The lungs of healthy humans have traditionally been considered to be sterile when examined by culture-based techniques. However, molecular identification techniques are now being used to explore the lung microbiome in ways that mirror study of other body sites and organ systems. Familiarity with population definitions and indices of diversity will lead to better understanding of the literature now coming to publication. Differences in methodology and sampling may contribute significantly to experimental variability, and the field has not coalesced around standard ways to present data or to perform statistical comparisons. This emerging and exciting field of investigation is leading to new ways of thinking about the lung and about lung disease.