Introduction: The intestinal microbiome is essential for immune system maturation. Infants born via C-section have altered intestinal microbiome composition compared to those born vaginally with decreased colonization of immune-stimulating anaerobes and increased colonization of potential pathogens. The clinical relevance of these changes is unclear. Infants with congenital heart disease (CHD) are at high risk for infection, particularly after surgery with cardiopulmonary bypass (CPB). The extent to which microbiome changes in infants with CHD born by C-section influence postoperative infection risk is unclear. Methods: We enrolled infants < 6 months of age who underwent cardiac surgery with CPB and collected fecal samples. We collected clinical data, including delivery mode, feeding method, CHD severity variables, and factors known to influence microbiome or outcomes, and assessed their contribution to postop infection. Postop infection was defined as a positive culture from a sterile site. We also tested whether specific features of the microbiome differed by mode of delivery. Fecal samples were analyzed using 16S rRNA sequencing, and absolute bacterial abundance was measured via digital droplet PCR. We compared standard microbiome metrics and abundance by mode of delivery and tested their association with infection. Results: We enrolled 31 patients < 6 months of age, 11 of whom were delivered via cesarean section, who underwent cardiac surgery with CPB at the Children’s Hospital of Michigan. There was no significant difference in absolute bacterial abundance by delivery mode. When analyzing prominent bacterial taxa, Dysgonomonas (p=0.016) and Lachnospiraceae (p=0.05) were more abundant in infants born by C-section. There was no significant difference in community composition between C-section and vaginal births, and slightly higher alpha diversity (Shannon) in infants born by C-section. Random forest analysis identified Dysgonomonas, preterm birth, and prior ICU stay as the strongest predictors of infection. C-section was not predictive of infection. Conclusions: In our study, there were some differences in the microbiota after heart surgery in infants born by C-section, but no difference in infection. Further studies should analyze microbiome composition and immune function in high-risk populations.
Blankenstein et al. (Sun,) studied this question.