There are no data regarding the activity of clarithromycin's active metabolite, 14-hydroxy clarithromycin, against penicillin-intermediate, penicillin-resistant or erythromycin-resistant Streptococcus pneumoniae. Agar dilution MICs were determined for clarithromycin, 14-hydroxy clarithromycin (henceforth called ‘metabolite’), azithromycin, erythromycin and clarithromycin/metabolite (2:1 and 1:1 ratio) against 24 penicillin-intermediate and 14 penicillin-resistant strains, including 13 erythromycin-resistant clinical strains and one ATCC strain of S. pneumoniae. The interaction between clarithromycin and its metabolite was determined using an agar chequerboard assay against all isolates, and time–kill tests were performed against five penicillin-intermediate (macrolide-susceptible) and five penicillin-resistant (two macrolide-resistant) strains of S. pneumoniae using all antibiotics alone at simulated peak serum concentrations, and clarithromycin/metabolite in a 2:1 ratio (physiological). MICs were as follows: clarithromycin, 0.008–>64 mg/L; metabolite, 0.015–>64 mg/L; erythromycin, 0.015–>64 mg/L; azithromycin, 0.125–>64 mg/L; clarithromycin/metabolite (1:1 and 2:1 combinations), 0.001–>64 mg/L. The MIC of the clarithromycin/metabolite combination was one or more tube dilution lower than the MIC of clarithromycin in 28 of the isolates tested. In chequerboard testing, 13 strains (seven erythromycin susceptible and six erythromycin resistant) demonstrated synergy, 18 additivity and seven indifference. In time–kill testing, bacterial eradication below detection limits occurred with clarithromycin and metabolite in seven of 10 organisms. The combination of parent and metabolite was more rapidly bactericidal than clarithromycin alone in six of the seven isolates (P = 0.026). The metabolite has potent activity against S. pneumoniae and enhances the activity of the parent compound against this organism. The metabolite's activity must be considered in evaluating clarithromycin in vitro to avoid underestimation of clarithromycin's activity against the pneumococcus.
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克拉霉素的活性代谢物 1
4-羟基
克拉霉素对
青霉素中度耐药、
青霉素耐药或
红霉素耐药肺炎链球菌的活性的数据。测定了
克拉霉素、1
4-羟基
克拉霉素(以下称为 "代谢物")、
阿奇霉素、
红霉素和
克拉霉素/代谢物(2:1 和 1:1 比率)对 24 株
青霉素中型菌株和 14 株
青霉素耐药菌株(包括 13 株
红霉素耐药临床菌株和 1 株 A
TCC 肺炎链球菌菌株)的
琼脂稀释 MIC。使用
琼脂棋盘试验测定了
克拉霉素及其代谢物与所有分离株之间的相互作用,并对 5 株
青霉素中级(对
大环内酯类药物敏感)和 5 株
青霉素耐药(对两种
大环内酯类药物耐药)的肺炎双球菌进行了时间致死试验,在模拟血清峰值浓度下单独使用所有抗生素,
克拉霉素/代谢物的比例为 2:1(生理学)。MIC 值如下:
克拉霉素,0.008->64 毫克/升;代谢物,0.015->64 毫克/升;
红霉素,0.015->64 毫克/升;
阿奇霉素,0.125->64 毫克/升;
克拉霉素/代谢物(1:1 和 2:1 组合),0.001->64 毫克/升。在测试的 28 个分离株中,
克拉霉素/代谢物组合的 MIC 比
克拉霉素的 MIC 低一个或多个试管稀释度。在棋盘试验中,13 株菌株(7 株对
红霉素敏感,6 株对
红霉素耐药)显示出协同作用,18 株显示出相加作用,7 株显示出不相干作用。在时间杀灭试验中,使用
克拉霉素和代谢物的 10 种
生物中有 7 种的细菌根除率低于检测限。与单用
克拉霉素相比,母体和代谢物的组合对七种分离菌中的六种的杀菌速度更快(P = 0.026)。代谢物对肺炎双球菌有很强的活性,并能增强母体化合物对该病菌的活性。在对
克拉霉素进行体外评估时,必须考虑代谢物的活性,以避免低估
克拉霉素对肺炎球菌的活性。