Objective：To investigate the distribution characteristics of oropharyngeal microbiota and the effects of different feeding methods on oropharyngeal microbiota colonization of healthy full term newborns in early -life. Methods：A total of 20 healthy term infants delivered between September 2021 and February 2022 at Shanghai Pudong New Area Health Care Hospital for Women and Children were recruited. According to feeding methods，infants were respectively divided into two groups，which were exclusively breastfeeding(n=8)and mixed-feeding(n=12). Oropharyngeal swab samples of all subjects were collected on the first day and day 5-7 after birth. The V3~V4 region of 16S rRNA gene was sequenced on Illumina MiseqTM/HiseqTM platform，and the results were analyzed by bioinformatics. Results：①36 phylum，84 class，144 order，292 family and 736 genus were identified in the 40 oropharyngeal swab samples. ②From day 1 to day 5~7 after birth，the relative abundance and diversity of oropharyngeal microbiota decreased gradually， and the differences between individuals decreased significantly. The α diversity of oropharyngeal microbiota in the exclusive breastfeeding group was lower than that in the mixed-feeding group. ③At the phylum level，Proteobacteria，Firmicutes，Actinobacteria and Bacteroidetes were the main phyla in different feeding groups. However，there was no significant difference in the four dominant phyla between two groups(P ＞ 0.05). Compared with day 1，the relative abundance of Firmicutes(P=0.008)，Actinobacteria(P=0.844)and Bacteroidetes(P=0.250)increased，but Proteobacteria decreased(P=0.055)on day 5~7 in the exclusive breastfeeding group；while Firmicutes(P ＜ 0.001)and Actinobacteria(P=0.733)increased，but Proteobacteria(P＜0.001)and Bacteroidetes(P=0.027)decreased in the mixed-feeding group. ④At the genus level，Bradyrhizobium，Staphylococcus，Acinetobacter，Burkholderia and Streptococcus were the main genera on day 1，while with the passage of birth time，Streptococcus，Staphylococcus，Bacteroides，Rothia and Bifidobacterium became the main genera at day 5~7. Streptococcus and Staphylococcus were the dominant genera in different feeding groups，and the abundance of Bacteroides，Rothia，Bifidobacterium and other anaerobes in exclusive breastfeeding group was higher than that in mixed- feeding group. Conclusion：The diversitly of oropharyngeal microbiota decrease gradually and the stability increased gradually in the early life of newborns. Different feeding methods have certain effects on the colonization and distribution of oropharyngeal microbiota in early life. Exclusive breastfeeding is helpful for the early colonization of anaerobes in the oropharynx of newborns.
