Smith K R, Cobbs C G
Department of Medicine, University of Alabama, Birmingham 35294.
Eur J Clin Microbiol Infect Dis. 1992 Jan;11(1):55-8. doi: 10.1007/BF01971273.
Fluoroquinolones are variably active against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). The purpose of this study was to test the in vitro susceptibility of 50 isolates each of MRSA and MRSE to four of the new fluoroquinolones--sparfloxacin, ciprofloxacin, ofloxacin and norfloxacin--and to see if resistance could be induced in five susceptible strains of each species by serial passages with increasing concentrations of drug. A standard microdilution technique was used to determine minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of each drug for each isolate. Agar dilution plates were also prepared containing concentrations of drug varying from one-half of the reported MIC to 128 times the reported MIC, and microorganisms persisting were serially passaged. Initially, 98% of the strains of MRSA were susceptible to the fluoroquinolones. MBCs were essentially identical to MICs. Similarly, 96% of the strains of MRSE were susceptible. Following exposure to increasing concentrations of each fluoroquinolone, resistance appeared to emerge less rapidly to sparfloxacin and ofloxacin than to norfloxacin and ciprofloxacin.
氟喹诺酮类药物对耐甲氧西林金黄色葡萄球菌（MRSA）和耐甲氧西林表皮葡萄球菌（MRSE）的活性各不相同。本研究的目的是检测50株MRSA和50株MRSE对四种新型氟喹诺酮类药物——司帕沙星、环丙沙星、氧氟沙星和诺氟沙星——的体外敏感性，并观察每种菌株的五株敏感菌株在连续传代过程中，随着药物浓度增加是否会诱导产生耐药性。采用标准微量稀释技术测定每种药物对每种分离株的最低抑菌浓度（MIC）和最低杀菌浓度（MBC）。还制备了琼脂稀释平板，其中药物浓度从报告的MIC的一半到报告的MIC的128倍不等，并对持续存在的微生物进行连续传代。最初，98%的MRSA菌株对氟喹诺酮类药物敏感。MBC与MIC基本相同。同样，96%的MRSE菌株敏感。在接触浓度不断增加的每种氟喹诺酮类药物后，司帕沙星和氧氟沙星诱导产生耐药性的速度似乎比诺氟沙星和环丙沙星慢。
