Development of the Human Mycobiome over the First Month of Life and across Body Sites.
Ward TL, Dominguez-Bello MG, Heisel T, Al-Ghalith G, Knights D, Gale CA
COMMENT: Early-life microbial colonization plays an important role in the healthy development of an infant. Extensive epidemiological surveys of the human microbiome have improved our understanding of how factors such as birth mode, diet, and exposure to antibiotics shape the bacterial microbiome in early life. Recent studies have also begun to elucidate key members of the bacterial community that may play specific roles in the health outcomes of infants. Studies characterizing infant microbial colonization have focused mostly on bacteria in the microbiome and have largely neglected fungi (the mycobiome), despite their relevance to mucosal infections in healthy infants.
The knowledge about the succession of fungal colonization in early life and whether it may relate to long-term health is scarce. To better understand fungal colonization and its sources, the authors studied the skin, oral, and anal mycobiomes of healthy term infants (n = 17) and the vaginal and anal mycobiomes of their mothers (n = 16) by internal transcribed spacer 2 (ITS2) amplicon sequencing.
Generally, infants were colonized by few fungal taxa, and fungal alpha diversity did not increase over the first month of life. There was no clear community maturation over the first month of life, regardless of body site. Key body-site-specific taxa, but not overall fungal community structures, were impacted by birth mode.
They found that infant mycobiomes differed by body site, with the infant mycobiomes at the anal sites being different from those at the skin and oral sites. The relative abundances of body site-specific taxa differed by birth mode, with significantly more Candida albicans fungi present on the skin of vaginally born infants on day 30 and significantly more Candida orthopsilosis fungi present in the oral cavity of caesarean section-born infants throughout the first month of life.
They also found the mycobiomes within individual infants to be variable over the first month of life, and vaginal birth did not result in infant mycobiomes that were more similar to the mother's vaginal mycobiome. Therefore, although vertical transmission of specific fungal isolates from mother to infant has been reported, it is likely that other sources (environment, other caregivers) also contribute to early-life mycobiome establishment.
Future longitudinal studies of mycobiome and bacterial microbiome codevelopment, with dense sampling from birth to beyond the first month of life, are warranted.