Laboratory of Microbiology, Dept Preclinical Sciences LITA Vialba, University of Milan, Via GB Grassi 74, Milan 20157, Italy.
BMC Microbiol. 2010 Apr 21;10:119. doi: 10.1186/1471-2180-10-119.
Fluoroquinolones are potent antimicrobial agents used for the treatment of a wide variety of community- and nosocomial- infections. However, resistance to fluoroquinolones in Enterobacteriaceae is increasingly reported. Studies assessing the ability of fluoroquinolones to select for resistance have often used antimicrobial concentrations quite different from those actually acquired at the site of infection. The present study compared the ability to select for resistance of levofloxacin, ciprofloxacin and prulifloxacin at concentrations observed in vivo in twenty strains of Escherichia coli and Klebsiella spp. isolated from patients with respiratory and urinary infections. The frequencies of spontaneous single-step mutations at plasma peak and trough antibiotic concentrations were calculated. Multi-step selection of resistance was evaluated by performing 10 serial cultures on agar plates containing a linear gradient from trough to peak antimicrobial concentrations, followed by 10 subcultures on antibiotic-free agar. E. coli resistant strains selected after multi-step selection were characterized for DNA mutations by sequencing gyrA, gyrB, parC and parE genes.
Frequencies of mutations for levofloxacin and ciprofloxacin were less than 10-11 at peak concentration, while for prulifloxacin they ranged from <10-11 to 10-5. The lowest number of resistant mutants after multistep selection was selected by levofloxacin followed by ciprofloxacin and prulifloxacin. Both ciprofloxacin- and prulifloxacin-resistant mutants presented mutations in gyrA and parC, while levofloxacin resistance was found associated only to mutations in gyrA.
Among the tested fluoroquinolones, levofloxacin was the most capable of limiting the occurrence of resistance.
氟喹诺酮类药物是一种强有力的抗菌药物，用于治疗多种社区和医院获得性感染。然而，肠杆菌科对氟喹诺酮类药物的耐药性日益增加。评估氟喹诺酮类药物选择耐药性的研究通常使用的抗菌浓度与实际感染部位获得的浓度有很大不同。本研究比较了左氧氟沙星、环丙沙星和普卢利沙星在 20 株从呼吸道和尿路感染患者中分离的大肠埃希菌和克雷伯菌中体内观察到的浓度下选择耐药性的能力。计算了在血浆峰和谷抗生素浓度下自发单步突变的频率。通过在含有从谷浓度到峰浓度的线性抗生素浓度的琼脂平板上进行 10 次连续培养，然后在无抗生素琼脂上进行 10 次亚培养，评估多步选择耐药性。多步选择后选择的耐药菌株通过测序 gyrA、gyrB、parC 和 parE 基因来鉴定 DNA 突变。
左氧氟沙星和环丙沙星的突变频率在峰浓度时小于 10-11，而普卢利沙星的突变频率在 10-11 到 10-5 之间。经过多步选择，左氧氟沙星选择的耐药突变体数量最少，其次是环丙沙星和普卢利氟沙星。环丙沙星和普卢利沙星耐药突变体均在 gyrA 和 parC 中发生突变，而左氧氟沙星耐药仅与 gyrA 中的突变有关。
在测试的氟喹诺酮类药物中，左氧氟沙星最能限制耐药性的发生。
