Bacterial Colonization in Neonates May Lead to Asthma

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Summary and Comment

Bacterial Colonization in Neonates May Lead to Asthma

Neonatal colonization with respiratory bacterial species was associated with childhood asthma in a prospective study.

Investigators in Denmark previously proposed that bacterial airway colonization during infancy might increase the risk for childhood asthma. Now, they have tested this hypothesis in a prospective study of 321 term or near-term infants born to women with asthma.

Hypopharyngeal samples were obtained at ages 1 and 12 months and were cultured for Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus. Parents recorded wheezing-related respiratory symptoms in daily diaries for up to 5 years; symptoms that persisted for $≥$ 3 days were confirmed by physicians.

At age 1 month, 61% of infants were colonized with S. aureus, and 21% of infants were colonized with S. pneumoniae, H. influenzae, M. catarrhalis, or some combination thereof. At 12 months, only 13% of infants were colonized with S. aureus, and 71% were colonized with one or more of the other bacteria. During 5 years of follow-up, neonatal colonization with S. pneumoniae, H. influenzae, or M. catarrhalis was significantly associated with an increased risk for persistent wheeze, acute severe exacerbation of wheeze, and hospitalization for wheeze; such colonization also was significantly associated with increased risk for asthma diagnosis at age 5. Colonization at 12 months was not associated with wheezing-related outcomes, nor was colonization with S. aureus.

Comment: These results provide some insight into a major public health problem among children. However, the mechanism by which neonatal colonization stimulates the pathogenetic processes that result in childhood asthma is unclear. The authors suggest that neonatal asthma is associated with a neutrophilic exudate that perhaps is caused by bacterial colonization, but I am unsure which is the chicken and which is the egg.

— Robert S. Baltimore, MD

Published in Journal Watch Infectious Diseases October 10, 2007