Because the disordered lung microbiome is involved in the pathogenesis of neutrophilic asthma and Th17/IL-17 plays a role in neutrophil recruitment in both bacteria-mediated diseases and asthma, there may be a link between Th17/IL-17-associated immune responses to some specific bacterial microbiota and the pathogenesis of severe or steroid-resistant neutrophilic asthma. This evidence concerns the gene IL17A and asthma.