Table 3.

Alterations in the preterm infant gut microbiota related to feeding type

Reference	Region	Sample size (n)			Sample time	Alterations in the GMa of PTIs
		MOM	DHM	Formula		MOM	DHM	Formula
Ford, et al. (2019)	USA	74	43	-	Within 6 weeks after birth	↑Alpha-diversity		-
					Week 4	↑Bacteroides, Bifidobacterium, and Enterococcus	↑Staphylococcus	-
Parra-Llorca, et al. (2018)	Spain	34	28	7	By the time of full enteral feeding	↓Clostridiaceae, ↑Bifidobacterium, Staphylococcus, Clostridium, Serratia, Coprococcus, Aggregatibacter, and Lactobacillus	↓Actinobacteria, ↑Bacteroidetes	-
							Acinetobacter genus was found	Bacteroidetes was highest; Staphylococcus and Klebsiella were dominant
Gregory, et al. (2016)	USA	10	10	10	First 60 days	Initial increase in diversity		Lactobacillales was highest
Wang, et al. (2020)	USA	10	-	10	At an average of 15 and 17 days after birth	Veillonella, Escherichia/Shigella, Staphylococcus, Clostridium, Enterococcus, and Streptococcus were dominant	-	↓Proteobacteria

^aGM, gut microbiota; PTIs, preterm infants; MOM, mother’s own milk; DHM, donor human milk