Bacterial colonisation predisposes to asthma

Infants who have certain types of bacteria (Streptococcus pneumoniae, Haemophilus influenzae or Moraxella catarrhalis) in their throats have a higher risk for developing recurrent wheeze, asthma or allergy early in life. Researchers from the Copenhagen University Hospital in Denmark assessed the development of recurrent wheeze and asthma in 321 newborns born to mothers with asthma. Throat aspirates of these 1-month-old infants were cultured for common respiratory pathogens – Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus. Wheeze was monitored prospectively on diary cards during the first 5 years of life and lung function was measured and asthma was diagnosed at 5 years of age. Twenty-one per cent of infants were colonised with S. pneumoniae, H. influenzae, M. catarrhalis, or a combination of these organisms. Colonisation with these organisms (but not Staphylococcus aureus) more than doubled the risk of persistent wheeze, wheeze flare-up and hospitalisation for wheeze. The prevalence of asthma at the age of five years was significantly increased in children who harboured these organisms as newborns compared with children who did not (33 per cent versus 10 per cent). The findings suggest that the presence and growth of bacteria in the throat in the first four weeks of life indicates a defective innate immune response very early in life, which promotes the development of asthma. This opens new perspectives for the understanding and prediction of recurrent wheeze and asthma in young children.