A 16S rRNA gene sequencing analysis to chart the intestinal microbiome development during infancy in full-term and preterm babies and the influence of early environmental exposures

Early life events such as mode of delivery, antibiotic exposure and feeding may influence intestinal microbiota colonisation and potentially lead to long-term consequences on wellbeing and diseases into adulthood. This is of particular importance for premature infants who spend the initial months of life in NICU. The aim of this thesis was to investigate the effect of early life influences on the development of gut microbiota in premature infants over the first year of life and compared with full-term infants. In addition, to identify the potential microbial signatures associated with atopy development at 1 year of age. 16s rDNA sequencing method was utilised to study a cohort of 245 preterm and 42 healthy full-term infants with sample collected at 4 time-points over the first year of life. The difference in gut microbiota composition between full-term and preterm infants remained detectable up to four months after birth. Difference in α-diversity and β-diversity during the first 4 weeks of life and differences in the ratio of Facultative Anaerobes to Strict Anaerobes (FA/SA) during the first four months of life among full-term infant was attributed to the mode of delivery. Type of feeding during hospitalisation was the most influential early life factor on the dynamic and development of gut microbiota among preterm infants. Preterm infants fed with probiotics showed similar patterns of microbiota colonization to full-term infants, which differed from the other preterm groups on different feeding regime. Feeding via exclusive human milk or mixed feeding of human milk and prebiotic enriched formula appeared to have minimal effect on the microbial development in preterm infants. The overall microbiota composition was different between non-atopic and atopic infants in full-term group but not in preterm group. Atopic full-term infants had significant higher Bacteroides/Bifidobacterium ratio than non-atopic infants at week-4 and month-4. Early and diverse microbiota colonization may appear to be critical for the ...