McGrath B J, Kang S L, Kaatz G W, Rybak M J
College of Pharmacy and Allied Health Professions, Wayne State University, Detroit, Michigan.
Antimicrob Agents Chemother. 1994 Sep;38(9):2034-40. doi: 10.1128/AAC.38.9.2034.
We adapted an in vitro pharmacodynamic model of infection to incorporate simulated endocardial vegetations. The bactericidal activities of teicoplanin, vancomycin, gentamicin, and various combinations of these drugs were studied against a strain of methicillin-susceptible Staphylococcus aureus obtained from a patient being treated for endocarditis at Detroit Receiving Hospital. Bacteria were grown overnight, concentrated, and added to a mixture of cryoprecipitate (80%) and thrombin (10%) to achieve approximately 5 x 10(9) CFU/g. Fibrin clots (8 to 10) were suspended into the model, removed at 24, 48, and 72 h in duplicate, weighed, and homogenized in 1.25% trypsin. Control experiments were conducted to characterize the growth kinetics. The following antibiotics were administered to simulate the pharmacokinetics of the drugs in humans: teicoplanin at 3 and 15 mg/kg of body weight, vancomycin at 15 mg/kg, and gentamicin at 1 mg/kg. Fibrin clot samples used to detect resistance were plated on antibiotic-containing tryptic soy agar plates. For the teicoplanin and vancomycin regimens, protein binding to cryoprecipitate, thrombin, and fibrin clot was determined to be 32, 43, and 50% and 26, 28, and 29%, respectively. In comparison with no treatment, vancomycin or teicoplanin at 15 mg/kg or either of these regimens combined with gentamicin significantly reduced bacterial counts (P < 0.0001). Monotherapy with teicoplanin at 3 mg/kg or gentamicin resulted in no killing activity. Combination treatment with teicoplanin at 3 mg/kg and gentamicin resulted in the killing of approximately 2 log10 CFU/g by 72 h and the development of resistance to gentamicin. The results obtained with the in vitro model of endocarditis are similar to the results reported by several investigators with the rabbit model of infective endocarditis. This unique infection model is useful for designing initial drug dosage regimens and may be predictive of drug efficacy against infective endocarditis.
我们调整了一种感染的体外药效学模型，使其纳入模拟的心内膜赘生物。研究了替考拉宁、万古霉素、庆大霉素以及这些药物的各种组合对从底特律接收医院一名正在接受心内膜炎治疗的患者身上分离出的一株甲氧西林敏感金黄色葡萄球菌的杀菌活性。细菌过夜培养、浓缩后，加入冷沉淀（80%）和凝血酶（10%）的混合物中，使其浓度达到约5×10⁹CFU/g。将8至10个纤维蛋白凝块悬浮于模型中，在24、48和72小时时重复取出，称重，并在1.25%的胰蛋白酶中匀浆。进行对照实验以表征生长动力学。给予以下抗生素以模拟药物在人体中的药代动力学：替考拉宁剂量为3和15mg/kg体重，万古霉素剂量为15mg/kg，庆大霉素剂量为1mg/kg。用于检测耐药性的纤维蛋白凝块样本接种于含抗生素的胰蛋白胨大豆琼脂平板上。对于替考拉宁和万古霉素治疗方案，测定其与冷沉淀、凝血酶和纤维蛋白凝块的蛋白结合率分别为32%、43%和50%以及26%、28%和29%。与未治疗相比，15mg/kg的万古霉素或替考拉宁，或这两种治疗方案与庆大霉素联合使用均显著降低了细菌数量（P<0.0001）。3mg/kg的替考拉宁或庆大霉素单药治疗均无杀菌活性。3mg/kg的替考拉宁与庆大霉素联合治疗在72小时时导致约2log₁₀CFU/g的细菌被杀灭，并出现对庆大霉素的耐药性。心内膜炎体外模型所获得的结果与几位研究者在感染性心内膜炎兔模型中报告的结果相似。这种独特的感染模型有助于设计初始药物剂量方案，并且可能预测药物对感染性心内膜炎的疗效。
