Microbiome and Exacerbations in Neutrophilic Asthma

Neutrophilic asthma (NA) is the least known severe asthma phenotype. It is associated with more exacerbations, worse control and impaired lung function. One of its possible etiologies is bronchial infections. The study of bronchial microbiology and its relationship with exacerbations is a new line of research.

Objectives: 1) To analyze bronchial microbiome in patients with AN and non-neutrophilic (ANN), with frequent exacerbations and without exacerbations. 2) To relate the presence of bronchial infections with differences in the microbiome. 3) Correlate the characteristics of the microbiome with other evidence used in exacerbations.

Methods: Prospective study involving 40 non-smoking asthmatics without bronchiectasis (20 with AN and 20 with ANN). Of these, 10 in each group will have frequent exacerbations (>2 rounds of systemic steroids in the last year, of >3 days each) and 10 non- frequent exacerbations. AN will be defined as >65% neutrophils in stable phase sputum. All patients will have two stable visits in which clinical variables, asthma control, lung function and induced sputum samples will be collected (for analysis of bronchial inflammatory cell count and for the study of the microbiome by 16 subunit rRNA). Specific Immunoglobulin A (IgA) for Chlamydia Pneumoniae will be determined. In exacerbations, sputum samples will be collected for culture and nasopharyngeal smears for the study of major respiratory viruses and bacteria by multiple polymerase chain reaction.