Figure 6: Reduced intestinal E. coli expansion by sialidase inhibition.

(a) In vitro growth of E. coli EHV2 in minimal media containing 10 mM Glc or 3SL and the presence of caecal fluid and inhibitor Neu5Ac2en (0, 20, 50 and 100 μM). (b) Levels of Neu5Ac in the caecal fluid of control, and inhibitor-treated WT mice (2 h post 0.5 mg Neu5Ac2en administration) were measured by HPLC analysis. Control mice were administered with sterile PBS. In (a,b), the data are represented as mean±s.e.m. from two independent experiments, N=5, *P<0.05 (two-tailed Student’s t-test). (c) Relative abundance of intestinal E. coli in control (PBS-treated) and Neu5Ac2en-treated WT mice (10 mg kg⁻¹ per day) was determined at day 8 after initiation of DSS challenge. Data are represented as median values from two independent experiments, N=6–8, *P<0.05 (two-tailed Student’s t-test). (d) Relative change in body weight of control and Neu5Ac2en-treated WT mice during DSS challenge for 5 days. Arrowheads indicate the time points of Neu5Ac2en administration. (e) Colon length was measured at day 8 after initiation of DSS challenge. In (d,e), the data are represented as mean±s.e.m. from two independent experiments, N=6–8, *P<0.05 (two-tailed Student’s t-test). (f) Representative histological sections of colon tissues from untreated WT mice (Mock), DSS-treated mice (DSS) and DSS-treated mice administered with sialidase inhibitor (DSS/Neu5Ac2en). Arrowheads indicate infiltrating leukocytes. Scale bar, 100 μm. (g) Scoring of colitis severity by quantitative examination of tissue alteration and leukocytes infiltration. Each dot indicates an individual animal from two independent experiments.