EFFECT OF GROWTH-CONDITIONS ON ANTIMICROBIAL ACTIVITY OF DU-6859A ANDITS BACTERICIDAL ACTIVITY DETERMINED BY THE KILLING CURVE METHOD

The effect of growth conditions on the antibacterial activity of DU-68 59a against Staphylococcus auerus, Escherichia coli, and Pseudomonas a eruginosa was compared with those of levofloxacin, sparfloxacin, and c iprofloxacin. This activity was not affected by different media, inocu lum size or the addition of human serum, but was decreased under acidi c conditions, in human urine, and in the presence of magnesium and fer rous ion, as were the other quinolones tested. Time-kill curve studies demonstrated the bactericidal action of DU-6859a against S. aureus, S treptococcus pneumoniae, E. coli, and P. aeruginosa. Morphological alt eration of these bacteria after exposure to DU-6859a also demonstrated its bactericidal activity. The frequency of spontaneous resistance to DU-6859a was less than or equal to those of the reference drugs.