Overview and diversity of the bacterial composition by clone library analysis. a) Shannon's diversity index on phylum level divided the NEC infants in two groups. This difference could not be explained by antibiotic treatments or the severity of the necrotizing enterocolitis b) The bacterial 16S rRNA gene composition from each of the eight necrotic intestinal tissue samples. Bacterial groups whose abundance were more than 10% in any sample are shown as bars. Enterococcus and Escherichia spp. were the most abundant in the samples with a low Shannon diversity index where Ralstonia sp. was the most frequent group of species in the samples with a high Shannon index.