Statistical Analyses

The results of bacterial count (log₁₀ cells per gram of feces) are expressed as mean ± standard deviation. The detection rate was expressed as the percentage of infants in which the specific bacterium was detected. During analysis in the spread-sheets to calculate the mean bacterial count and the detection rate, the cells were left blank if the specific bacterium was not detected (i.e., below the detection limit) in a sample. The count of genus Lactobacillus was expressed as the sum of the counts of six subgroups (L. casei subgroup, L. gasseri subgroup, L. plantarum subgroup, L. reuteri subgroup, L. ruminis subgroup, and L. sakei subgroup) and two species (L. brevis and L. fermentum). The comparisons of fecal bacterial counts by the mode of delivery were calculated by unpaired Student’s t-test. Differences in the detection rate of bacteria were calculated by Fisher’s exact probability test. P < 0.05 was considered statistically significant.