Penders J et al. (2007) Gut microbiota composition and development of atopic manifestations in infancy: the KOALA Birth Cohort Study. Gut 56: 661–667

Emerging evidence now suggests that the dramatic increases in the prevalence of childhood atopy in Western countries in recent decades result from Western diet and antibiotic use, rather than from reduced exposure to infections. Diet and antibiotics could perturb infant gut microbiotic composition, resulting in disruption of normal development of immune tolerance.

In this prospective, national study of 957 eligible infants (whose mothers were participants in the KOALA study), Penders et al. aimed to determine whether the presence or load of colonizing bacteria in 1-month-old infants (as determined by quantitative real-time polymerase chain reaction analysis of fecal samples) was associated with atopic symptoms in children aged up to 2 years. Parents provided questionnaire information on atopic symptoms and potential confounders at study enrollment (34 weeks' gestation) and months 3, 7, 12 and 24 postpartum. Trained nurses took blood samples from, and performed a physical examination for atopic dermatitis in, the 607 24-month-old-infants available for home visit.

After adjustment for confounders (subcohort, parental and sibling atopic history, age at fecal sample collection, infant's sex), the presence of Clostridium difficile was associated with a higher risk of all atopic outcomes: eczema (odds ratio [OR] 1.4), recurrent wheeze (OR 1.75), allergic sensitization (OR 1.54) and atopic dermatitis (OR 1.73). The presence of Escherichia coli was associated with a higher risk of eczema (OR 1.87); this risk increased with increasing count.

The findings provide support for a causal relationship between disturbances in infant gut microbiota composition and subsequent development of atopy.