Figure 1.

Schematic overview of antibiotic-altered microbiota experiments. The caecum of conventional mice (normal microbiota) exhibited low sialic acid levels compared to antibiotic-treated mice (altered microbiota). C. difficile mutant expansion was significantly compromised in conventional mice and the C. difficile nan operon was highly induced in antibiotic-treated mice. S. Typhimurium mutants displayed a competitive defect in antibiotic-treated mice relative to conventional mice. All results are consistent with the concept that liberated sialic acid allows for the growth and proliferation of WT S. Typhimurium and C. difficile within an antibiotic-disturbed gut microbiota.