TABLE 1.

Demographic and clinical information of infants enrolled in the study.

Infants ID (#)	Nutrition	Gender	Infant antibiotic use	Delivery type	Race/Ethnicity	Twin pair
1	Formula	F	0	Cs	C
2	Breast milk	M	1	Cs	C
3	Breast milk	F	0	Cs	C
7	Formula	F	0	V	N	A
8	Formula	M	0	V	N	A
9	Breast milk	M	0	Cs	C	B
10	Breast milk	M	0	Cs	C	B
11	Breast milk	F	1	V	C
13	Breast milk	F	0	Cs	C
15	Formula	M	0	V	N
16	Breast milk	F	1	V	C
18	Formula	M	1	Cs	N	C
19	Formula	F	1	Cs	N	C
20	Breast milk	F	1	V	C
21	Breast milk	F	1	Cs	C	D
22	Breast milk	F	1	Cs	C	D
23	Formula	M	1	Cs	C	E
24	Formula	M	1	Cs	C	E
25	Formula	F	1	Cs	N
27	Formula	M	0	Cs	C

Gender: F, female; M, male. Infant antibiotic use: 0, non-antibiotics; 1, received ampicillin/gentamicin antibiotic treatment. Delivery type: Cs, cesarean section; V, vaginal delivery. Race/Ethnicity: C, Caucasian; N, Native American. Twins: five pairs of twins were included – A, B, C, D, and E.