Modulation of the intestinal flora of mice by treatment with aztreonam and tigemonam.

Oral and parenteral administration of aztreonam and oral administration of tigemonam to conventional mice caused a decrease in the number of aerobic gram-negative rods in the feces. Oral treatment with high doses of aztreonam (greater than or equal to 25 mg/kg/day) and tigemonam (100 mg/kg/day) adversely influenced colonization resistance, whereas oral treatment with lower doses of the monobactams or parenteral treatment with aztreonam did not.