InVitro Antibacterial Activity ofa New Quinolone, NM394

andPseudomonas aeruginosa was equaltoor one-half thatofciprofloxacin. NM394was as active as ofloxacin against gram-positive bacteria andwas twotoeight times more active against gram-negative bacteria, including P. aeruginosa. NM394was twotoeight times more active thanenoxacin against gram-positive andgram-negative bacteria. TheMICsofNM394against Escherichia coilandP.aeruginosa atpH5.5were reduced 4to16times compared withthose atpH7.0. Ciprofloxacin, ofloxacin, andenoxacin were 2to32timesless active against these twobacteria andStaphylococcus aureusatan acidic pHthanthey were atpH7.0. Inthepresenceof5 mM Mg2+,theMICsofaUl ofthese drugs increased 2to32times, butthey were onlyslightly affected by5mM Ca2,typeofmedium, serum,orsize ofinoculum. NM394showed potent bactericidal activity andinhibited thesupercoiling activity ofE.coli DNA gyrase.Theinvitro antibacterial profile ofNM394issimilar tothatof other 6-fluoroquinolones.