Purpose of review: Colonization of the newborn intestine is a complex process evolving over the first year of life. It is partly responsible for guiding immunologic development within the infant. Given the sharp escalation in immunologic diseases such as allergy and inflammatory bowel disease (IBD), this microbial-host interaction has become the focus of intense interest. DNA-based detection techniques have allowed increased identification of specific microbes involved in this symbiosis.
Recent findings: Epidemiologic studies have demonstrated a link between allergic diseases and alterations in the colonizing flora of infants. Concurrently, other work has demonstrated that interactions between gut flora and the intestinal epithelium seem to be central to the pathogenesis of IBD. In both allergy and IBD, certain bacteria seem to provide beneficial, protective effects via immune modulation.
Summary: There is a complex interaction between the bacteria within the developing gut and the immune system of the host. Colonization of the neonatal gut represents a critical window in this process. It appears clear that disruption within this flora has long-term health consequences as diverse as eczema, allergic rhinitis, and IBD. Guided establishment of specific species within the flora may reduce the incidence of these diseases.