AUTHOR=Nagpal Ravinder , Tsuji Hirokazu , Takahashi Takuya , Kawashima Kazunari , Nagata Satoru , Nomoto Koji , Yamashiro Yuichiro 

TITLE=Sensitive Quantitative Analysis of the Meconium Bacterial Microbiota in Healthy Term Infants Born Vaginally or by Cesarean Section

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01997

DOI=10.3389/fmicb.2016.01997

ISSN=1664-302X

ABSTRACT=<p>For decades, babies were thought to be born germ-free, but recent evidences suggest that they are already exposed to various bacteria <italic>in utero</italic>. However, the data on population levels of such pioneer gut bacteria, particularly in context to birth mode, is sparse. We herein aimed to quantify such bacteria from the meconium of 151 healthy term Japanese infants born vaginally or by C-section. Neonatal first meconium was obtained within 24–48 h of delivery; RNA was extracted and subjected to reverse-transcription-quantitative PCR using specific primers for <italic>Clostridium coccoides</italic> group, <italic>C. leptum</italic> subgroup, <italic>Bacteroides fragilis</italic> group, <italic>Atopobium</italic> cluster, <italic>Prevotella, Bifidobacterium</italic>, <italic>Lactobacillus</italic>, <italic>Enterococcus</italic>, Enterobacteriaceae, <italic>Staphylococcus</italic>, <italic>Enterococcus</italic>, <italic>Streptococcus</italic>, <italic>C. perfringens</italic>, and <italic>C. difficile</italic>. We detected several bacterial groups in both vaginally- and cesarean-born infants. <italic>B. fragilis</italic> group, Enterobacteriaceae, <italic>Enterococcus</italic>, <italic>Streptococcus</italic>, and <italic>Staphylococcus</italic> were detected in more than 50% of infants, with counts ranging from 10<sup>5</sup> to 10<sup>8</sup> cells/g sample. About 30–35% samples harbored <italic>Bifidobacterium</italic> and <italic>Lactobacillus</italic> (10<sup>4</sup>–10<sup>5</sup> cells/g); whereas <italic>C. coccoides</italic> group, <italic>C. leptum</italic> subgroup and <italic>C. perfringens</italic> were detected in 10–20% infants (10<sup>3</sup>–10<sup>5</sup> cells/g). Compared to vaginally-born babies, cesarean-born babies were significantly less often colonized with <italic>Lactobacillus</italic> genus (6% vs. 37%; <italic>P</italic> = 0.01) and <italic>Lactobacillus gasseri</italic> subgroup (6% vs. 31%; <italic>P</italic> = 0.04). Overall, seven <italic>Lactobacillus</italic> subgroups/species, i.e., <italic>L. gasseri</italic> subgroup, <italic>L. ruminis</italic> subgroup, <italic>L. casei</italic> subgroup, <italic>L. reuteri</italic> subgroup, <italic>L. sakei</italic> subgroup, <italic>L. plantarum</italic> subgroup, and <italic>L. brevis</italic> were detected in the samples from vaginally-born group, whereas only two members, i.e., <italic>L. gasseri</italic> subgroup and <italic>L. brevis</italic> were detected in the cesarean group. These data corroborate that several bacterial clades may already be present before birth in term infants’ gut. Further, lower detection rate of lactobacilli in cesarean-born babies suggests that the primary source of lactobacilli in infant gut is mainly from maternal vaginal and–to a lesser extent–anal microbiota during vaginal delivery, and that the colonization by some important <italic>Lactobacillus</italic> species is delayed in babies delivered via cesarean-section.</p>