Fig. 6

Relative abundance of different microbial groups in guts of preterm infants undergoing antibiotic prophylaxis at high/low doses. a At the phylum level. b At the genus level. On d14 gut microbiota were generally dominated by the phyla Proteobacteria (79.35% in the H group vs. 70.66% in the L group) and Firmicutes (19.33% in the H group vs. 14.81% in the L group). At the genus level, on d14 the microbiota structure in both groups was similar. The gut microbiota of the two groups remained predominantly populated with members of Klebsiella (55.91% in the H group vs. 36.15% in the L group) and Enterococcus (23% in the H group vs. 34.22% in the L group). Shigella and Streptococcus had a tendency to decrease in the H group