FIGURE 2: Schematic time course of Bifidobacterium abundance from the age of 2 years to 6 years. The abundance of Bifidobacterium naturally declines at this age as the microbiota mature, but macrolide courses (red arrows) cause a transient loss of Bifidobacterium, which is replaced by LPS-producing Gram-negative bacteria. This may result in the weakening of intestinal barrier, potentially causing increased translocation of LPS into the circulation (pink zones).