Mice subjected to antibiotic treatment displayed heightened susceptibility to DSS-induced colitis as shown in the increased weight loss (Fig. 1H), disease activity indices (Fig. 1I), and higher colonic myeloperoxidase (MPO) activity (Fig. 1K), but less prone to inflammatory response than SPF colitis mice, as evidenced by the lower secretion of IL-10 in colon tissue (Fig. 1L), up-regulated Il-6 gene level, and the down-regulated Tnf-α and Il-1β expression (Fig. 1M). Here, MPO is linked to colitis.