Impact of a new quinolone, DU-6859a, and two oral carbapenems, CS-834 and L-084, on the rat and mouse caecal microflora

We determined the influence of a new quinolone, DU-6859a, and two oral carbapenems, CS-834 and L-084, on the rat and mouse caecal microflora. The caecum-skin fistula-implanted rats and conventional mice were given oral antimicrobials at doses of 30 mg/kg bid for 5 days. DU-6859a generated a marked decrease in the numbers of caecal flora except for enterococci. CS-834 and L-084 had little impact on the rat caecal flora. CS-834 caused a great decrease in the numbers of mouse caecal flora but L-084 did not. In vitro studies suggest that the difference is due to the extension of inactivation of antimicrobials by caecum contents.