Variation of cultured skin microbiota in mothers and their infants during the first year postpartum

Background/Objectives The establishment of newborn skin flora depends on the ongoing skin maturation and the existence of potential microbial colonizers within the environment of the infant during a period of intense mother-infant physical interaction. This longitudinal study assessed culturable skin bacteria in the mother-infant dyad during the first year of life. Methods A total of 17 mother-infant dyads were swabbed within 24 hours postpartum and at 3, 6, 9, and 12 months. Skin swabbing was performed on two anatomical areas per individual (mothers: chest-abdomen; infants: forehead-buttocks) and were incubated in five different solid culture media to optimize yield. Isolated bacterial species were identified to genus or species level using the API system (BioMerieux, Marcy l'Etoile, France). Results A total of 444 microbial strains were isolated belonging to 22 genera: 6 "frequent" (isolated from > 5% samples: S aureus, Proteus, Klebsiella, Pseudomonas, Enterobacter, and Enterococcus) and 16 "infrequent." Isolated genera per individual peaked at 6 months postpartum for mothers and infants (P < 0.05). Enterobacter, Enterococcus, Klebsiella, and Pseudomonas isolation rates varied significantly as a function of sampling time contrary to the rather constant isolation rates of Proteus and S aureus. The rates of concordant isolation of the same microbial species within the mother-infant dyad tended to drop from birth to the end of the first year postpartum. Conclusions Distinct variations in the isolation rates of skin commensals from specific anatomical sites of the mother-infant dyad indicate bidirectional microbial transmission. Increasing skin flora individuality of the growing infant was recorded, manifested by declining rates of concordant isolation of the same microbial species from mother and her infant.