Mice were exposed to a previously published broad-spectrum regimen of enteric antibiotics as previously described (34 (link)). The following concentrations of antibiotics were administered via drinking water for 3 weeks before oxygen exposure: ampicillin (1 g/liter; Sigma-Aldrich), neomycin sulfate (1 g/liter; Sigma-Aldrich), metronidazole (1 g/liter; Sanofi-Aventis), and vancomycin (0.5 g/liter; Sandoz).