Foleno B D, Lafredo S C, Fu K P
R. W. Johnson Pharmaceutical Research Institute, Raritan, N.J. 08869.
Chemotherapy. 1993 Mar-Apr;39(2):120-3. doi: 10.1159/000239112.
The in vitro activity of levofloxacin against coagulase-negative staphylococci (CNS) was investigated. In vitro, on the basis of MIC90 values, levofloxacin was as active as ciprofloxacin, inhibiting both methicillin-sensitive and -resistant staphylococci at 0.5 microgram/ml. The frequency of one-step development of levofloxacin-resistant CNS was < 1 x 10(-9). After repeated transfer of CNS in the presence of increasing concentrations of levofloxacin or other quinolones, there were 4-fold increases in MIC50 values for both levofloxacin and ofloxacin, whereas there were 64- to 128-fold increases for ciprofloxacin, norfloxacin and enoxacin. Based on MIC50 values, the concentrations of 1 or 2 micrograms/ml are clinically relevant. The mutant strains induced by levofloxacin showed less virulence based on the LD50 value in acute systemic murine infection.
研究了左氧氟沙星对凝固酶阴性葡萄球菌（CNS）的体外活性。在体外，基于MIC90值，左氧氟沙星与环丙沙星活性相当，在0.5微克/毫升时可抑制甲氧西林敏感和耐药葡萄球菌。左氧氟沙星耐药CNS一步产生的频率<1×10^(-9)。在浓度不断增加的左氧氟沙星或其他喹诺酮类药物存在下对CNS进行反复传代后，左氧氟沙星和氧氟沙星的MIC50值增加了4倍，而环丙沙星、诺氟沙星和依诺沙星的MIC50值增加了64至128倍。基于MIC50值，1或2微克/毫升的浓度具有临床相关性。在急性全身性小鼠感染中，基于LD50值，由左氧氟沙星诱导的突变菌株显示出较低的毒力。
