cultures of babies with late-onset sepsis. Unpublished data from Neu’s research group show lower overall microbial diversity in sepsis babies 2 weeks before diagnosis, with few Proteobacteria detected. At the onset of sepsis, Proteobacteria bloom, which Neu observed is similar to what happens with NEC.

C-Section Versus Vaginal Delivery: Microbiome Differences

Neu explored in more detail a subject that Lita Proctor touched on, that is, microbiome differences between babies born vaginally versus those born via C-section. It is an important topic, Neu argued, because of the impact of the microbiome on development of the immune system during the first year of life and because of the growing number of C-section deliveries worldwide. In the United States, C-sections have increased from 24 to 34 percent over the past 15 years; in large cities in China, C-section delivery rates reach 60 percent; and in some South American countries, for example, Argentina and Brazil, C-section deliveries in private hospitals approximate 100 percent. Neu and Rushing (2011) listed a range of health outcomes associated with C-section deliveries, including allergic rhinitis, asthma, celiac disease, diabetes mellitus, and gastroenteritis.

With C-section delivery, lack of exposure to the vaginal microbiota results in “abnormal” microbial seeding of the GI tract and “abnormal” development of immunity, according to Neu. Dominguez-Bello and colleagues (2010) reported that with vaginal delivery, the baby’s first stool microbiota closely resembled the mother’s vaginal microbiota, whereas with C-section delivery, the baby’s first stool microbiota closely resembles the mother’s skin microbiota. Neu mentioned some unpublished data that show not only differences in microbial presence between C-section and vaginal deliveries, but also changes in those differences over time. Major phylum-level differences that exist at week 1 (e.g., greater Proteobacteria abundance in C-section babies, greater Bacteroides abundance in vaginal babies) disappear by week 4, while certain genus-level differences that are not present at week 1 emerge at week 4 (e.g., relative abundance of Enterococcus).

Pediatric Microbiome: Implications for Long-Term Health and Disease

In conclusion, Neu briefly described yet another early-life disease, type 1 diabetes, that has been associated with the pediatric microbiome. In addition to genetic predisposition and other factors, researchers have found significant differences in microbial ecology between children who develop type 1 diabetes and children who do not (Brown et al., 2011; Vaarala et al., 2008). Butyrate-producing bacteria appear to be especially important for maintaining a healthy gut and preventing type 1 diabetes (see Figure 3-1).

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