新生儿早期通过母婴传播的菌群分析

Cell Host and Microbe刚刚上线的另一项母婴菌群传递的研究中，在44对母婴中，在菌株水平揭示了母亲向孩子传递肠道细菌的两种主要模式及决定因素，并分析了抗生素耐药基因在母婴间传播的情况。

论文摘要

Bacterialcommunity acquisition in the infant gut im- pacts immune education and diseasesusceptibility. We compared bacterial strains across and within families in aprospective birth cohort of 44 infants and their mothers, sampledlongitudinally in the first months of each child’s life. We identified mother-to-child bacterial transmission events and describe the incidence offamily-specific antibiotic resistance genes. We observed two inheritancepatterns across multiple species, where often the mother’s dominant strain istransmitted to the child, but oc- casionally her secondary strains colonize theinfant gut. In families where the secondary strain of B. uniformis wasinherited, a starch utilization gene cluster that was absent in the mother’sdomi- nant strain was identified in the child, suggesting the selectiveadvantage of a mother’s secondary strain in the infant gut. Our findings revealmother- to-child bacterial transmission events at high reso- lution and giveinsights into early colonization of the infant gut.

The infant gutmicrobial community plays an important role in human development, including thematuration of the immune system (Smith et al., 2013),nutrient utilization and modification (Nicholson et al., 2012; Sela et al., 2008), and the prevention of pathogencolonization (Sela and Mills,2010). This dynamiccom- munity is strongly affected by delivery mode (Biasucci et al., 2010; Dominguez-Bello etal., 2010; Jakobsson et al., 2014; Pen- ders et al., 2006; Yassour et al., 2016) and feeding (Ba€ckhed et al., 2015) and stabilizes by age 3, when it starts toresemble an adult gut community (Yatsunenko et al., 2012).Although considerable progress has been made in characterizing the taxonomicprofiles of these early-life gut communities (Ba€ckhed et al., 2015; Dominguez-Bello etal., 2010; Koenig et al., 2011; Yassour et al., 2016), questions concerning their origin and theextent of maternal transmission contributions remain largely unanswered (Perez-Mun ̃ oz et al., 2017). Here, longitudinal sam- pling from bothmother and child, coupled with deep metage- nomic sequencing, enables us to usestrain-level analysis to bridge this knowledge gap.

Children areexposed to diverse environmental sources of bacteria from the day they are born,yet which of these bacteria will end up colonizing their gut is still onlypartially understood. Multiple factors can influence this selection process,including the microbial composition of potential maternal sources (e.g.,vaginal/gut communities), the state of immune activation in the host (Cahenzli et al., 2013; Olszak et al., 2012), and the carbon sources found in the uniqueenvironment of the infant gut (Mar- cobal et al., 2011; Sela et al., 2008). Importantly, while the mother’s own gutbacteria provide a likely source of continual exposure, we know little aboutvertical inheritance events in determining early childhood gut composition.Such postnatal vertical transmission of the mother’s gut bacteria may provideearly colonizers that can reside in the child’s gut for many years (Faith et al., 2013).

Strain-level variations among isolated bacteria havebeen studied for over a century using culture-based methods, but metagenomicsequencing and new computational approaches have only recently become availableas important new tools to study strain variation in culture-free environmentalsamples and complex mixtures of bacteria (Luo et al., 2015; Truong et al., 2017). Different strains of the same species often share80%–90% of their genes, referred to as the species core genome. However, thenon-core genome confers important functional differences, such as antibioticresistance (AR) and car- bon source utilization, which may play an importantrole in the selection process in various environmental niches. The ability todetect such strain differences in early life and infer their func- tionalconsequences remains a challenge for the field.

实验综述

① 在44对母婴中，分析婴儿出生头3个月的肠道菌群动态，纵向评估母亲向婴儿传递肠道细菌的模式；

② 对某个菌种而言，多数情况下，孩子会继承母亲的优势菌株，但次要菌株的传递也时有发生；

③ 次要菌株的定殖似乎是由功能选择所驱动，比如：当母亲的单形拟杆菌的主要菌株缺乏促进代谢母乳的淀粉利用基因时，具有该基因的次要菌株可在孩子肠道内定殖；

④ 母亲菌群中的抗生素耐药基因也会传递给孩子。