NEW YORK (GenomeWeb) – Publishing their results today in a brief communication in Nature, a multi-center team has demonstrated for the first time that they can alter the microbiomes of babies delivered via cesarean section, bringing them closer to what is seen in vaginally delivered infants.
The effort is only a first step toward determining whether this type of microbiome restoration has any clinical benefit, something that will require much larger numbers of subjects followed over long time periods to resolve, the researchers said.
Epidemiological studies, while not proving a causal relationship, have shown that C-sections are associated with a variety of undesirable effects for children, including an increased risk for allergies, immune disorders, and metabolic conditions. Differences in the microbiomes of C-section versus vaginally delivered babies has been posited as a potential mechanism for these outcomes.
In the new study, researchers from NYU, Mount Sinai, and several other institutions, recruited a total of 18 mothers and infants — seven born vaginally and 11 delivered by C-section at the University of Puerto Rico hospital in San Juan — to test a protocol that involved swabbing the newborns' mouths, faces, and then the rest of their bodies, with a piece of gauze that had been incubated in the vagina of their mother for about an hour prior to the C-section surgery.
The team treated four of the C-section infants with this swabbing approach, while leaving the other three untreated.
Using a sequencing protocol targeting the V4 region of the 16S rRNA gene, as well as a variety of bioinformatics and statistical tools, the researchers were able to track the composition of the microbiota and how it changed over time in vaginally delivered, swabbed C-section, and unswabbed C-section newborns.
In all, the team collected about 15,000 samples and sequenced about 1,000 from the mothers' and infants' bodies at several time points in order to compare the three different groups.
Analyzing the sequencing results, the team found that the swabbed C-section infants were enriched for vaginal bacteria like Lactobacillus and Bacteroides — two bacterial families that have been linked to proper development of the immune system.
Though not a complete match, the swabbed babies seemed to achieve a microbial community in several sites of their body that looked much more like that of the vaginally delivered babies than that of the untreated infants, in (and on) whom these vaginal bacteria were largely absent.
One reason swabbed C-section infants may not achieve a full match of the microbiome conferred in vaginal delivery could be the relatively short period of exposure with swabbing compared to a labor than can last many hours, the authors wrote.
Though yet untested, in future studies an enhanced protocol that exposes newborns to maternal vaginal gauze swabbing repeatedly, rather than a single time, might potentially work better, the group hypothesized.
Absent in the results of this initial experiment is any evidence of whether the swabbing procedure actually influences the health of C-section babies. This will require longitudinal tracking of much larger cohorts, the authors wrote, something the NYU team is pursuing.
"This study has allowed us to demonstrate the feasibility of bacterial restoration in a small cohort, but we do not know yet whether this procedure alone is sufficient to restore the health benefits associated with vaginal delivery. … Studies that target children at risk for immune disorders, such as allergies, will be required to determine how microbial restoration affects health outcomes," Jose Clemente, one of the study's lead authors, said in a statement.