Analysis of microbial colonies from the first-pass meconium of healthy neonates: Comparison of vaginally and cesarean section born

Background: The colonization and diversification of early microbes in the infant digestive tract are crucial to the health and pathophysiology of all neonates. Fundamentally, whether the gut is sterile at birth is the key question in understanding human microbial colonization. Although the gut of an infant at birth has long been believed sterile, this paradigm has been challenged. Objectives: To confirm or reject the fist-pass meconium is sterile. Methods: The first-pass meconium of healthy term infants was collected and examined by the bacterial inoculation and identification, and molecular analysis. Results were correlated with their delivery modes. First-pass meconium was immediately collected from 60 full-term newborns. Fresh meconium was examined by the bacterial inoculation and identification. DNA was extracted from the meconium samples for real-time polymerase chain reaction. The comparisons of fecal bacterial counts by the mode of delivery were calculated by using unpaired Student’s t test. Differences in the detection rate of bacteria were calculated by Fisher’s exact probability test (Statistical Package for the Social Sciences [SPSS], version 10). P < 0.05 was considered statistically significant. Results: In the vaginally born (VB) group, 46.34% of meconium samples had detectable microbes, which were associated with vaginosis and existed in the urine and stool. In the cesarean-section born (CB) group, although microbes could not be isolated by the traditional bacterial culture methods, the bacterial counts and bacterial DNAs were detected by molecular technology. Conclusion: Meconium is not sterile. Bacteria were present in the first-pass meconium of term, healthy, VB and CB infants.