Development and Functions of the Infant Gut Microflora: Western vs. Indian Infants

Table 1

Evolution of the gut microflora in Western breastfed infants [1, 14, 55, 57, 58].

Phase of infancy		Family/genus/species	Phylum	Aerobic/anaerobic
Initial phase of bacterial acquisition (first 1-2 weeks after birth)	Immediately after birth	Escherichia coli	Proteobacteria	Facultative anaerobe
		Streptococcus	Firmicutes	Facultative anaerobe
	Subsequently	Staphylococcus	Firmicutes	Facultative anaerobe
		Enterococcus	Firmicutes	Facultative anaerobe
		Lactobacillus	Firmicutes	Facultative anaerobe/microaerophile
	Postnatal day 4-7	Bacteroides	Bacteroidetes	Obligate anaerobe
		Bifidobacterium	Actinobacteria	Anaerobe
		Clostridium	Firmicutes	Obligate anaerobe
Remaining period of exclusive breastfeeding (up to approximately 4 months of age)		Bifidobacterium (predominant)	Actinobacteria	Anaerobe
		E. coli (decrease in proportion)	Proteobacteria	Facultative anaerobe
		Streptococcus (decrease in proportion)	Firmicutes	Facultative anaerobe
		Bacteroides (decrease in proportion)	Bacteroidetes	Obligate anaerobe
		Clostridium (decrease in proportion)	Firmicutes	Obligate anaerobe
From introduction of solid food (4-6 months of age) to cessation of breastfeeding (around 1 year of age)		Enterobacteriaceae	Proteobacteria	Facultative anaerobe
		Enterococcus	Firmicutes	Facultative anaerobe
		Bacteroides	Bacteroidetes	Obligate anaerobe
		Clostridium	Firmicutes	Obligate anaerobe
		Anaerobic Streptococcus	Firmicutes	Anaerobe
		Bifidobacterium	Actinobacteria	Anaerobe
		Lactobacillus	Firmicutes	Facultative anaerobe/microaerophile
After completion of weaning (approximately 2 years of age)		Gut microflora begins to resemble that of adults