Inflammatory phenotypes are recognised in stable adult asthma, but are less established in childhood and acute asthma. Additionally, Chlamydophyla pneumoniae infection as a cause of noneosinophilic asthma is controversial. This study examined the prevalence of inflammatory phenotypes and the presence of current Chlamydophyla pneumoniae infection in adults and children with stable and acute asthma.

Adults with stable(n=29) or acute(n=22) asthma, healthy adults(n=11), and children with stable(n=49) or acute(n=28) asthma and healthy children(n=9) underwent clinical assessment and sputum induction. Sputum was assessed for inflammatory cells, and DNA was extracted from sputum cell suspensions and supernatant for Chlamydophyla pneumoniae detection using real-time PCR.

Asthma phenotype was predominantly eosinophilic in children with acute asthma (50%) but neutrophilic in adults with acute asthma (82%). Paucigranulocytic asthma was the most common phenotype in both adults and children with stable asthma. Chlamydophyla pneumoniae was not detected in 99% of samples.

The pattern of inflammatory phenotypes differs between adults and children, with eosinophilic inflammation being more prevalent in both acute and stable childhood asthma, and neutrophilic inflammation being the dominant pattern of acute asthma in adults. The aetiology of neutrophilic asthma is unknown and is not explained by the presence of current active Chlamydophyla pneumoniae infection.