Moroizumi S, Kasitani F, Isikawa M, Iwata M, Ohno A, Yamaguchi K
Department of Clinical Laboratory, Omori Hospital, Toho University, Tokyo.
Rinsho Byori. 1994 Oct;42(10):1062-8.
Disc diffusion technique is useful to routine drug susceptibility testing for bacteria in clinical laboratories because of the advantages on simplicity and cost. Kirby-Bauer (KB) method recommended by NCCLS is using widely as a standard method of disk diffusion test, and simply categorize microorganisms as being susceptible, moderately susceptible, intermediate or resistant to different antimicrobial agents by the use of break point. In the determination of breakpoints, the relationship between MICs and clinical results and pharmacokinetics parameters (Cmax, T1/2 and AUC) are significantly considered. However, there are variance of pharmacokinetics among a race, moreover, breakpoint is not yet established in Japan. In report to doctor from clinical laboratory, the MIC might be better than that by breakpoint since there are such problems of breakpoint. Showa disk was developed as mono-disk method being able to deduce MIC from the linear regression between MIC and zone diameter. Therefore, it is thought that Showa disk is one of valuable methods for the routine drug susceptibility testing for bacteria in Japan. There is one problem, which is that MIC deduced by Showa disk is based on the relationship with agar dilution method although the determination method of MIC is going to turn into micro-dilution method, so we compared the MICs deduced from zone diameter of Showa disk method with the MICs determined by broth micro-dilution method by using a challenge set of 110 gram-positive and gram-negative bacteria for 7 antimicrobial agents. The total agreement of MIC within 1-log2 dilution difference was 77% and the correlation coefficient was 0.929. As results, a good relationship was obtained except the results of tetracycline and ofloxacin for beta-lactamase non-producing H. influenzae, and ceftizoxime for E. coli, and K. pneumoniae.
纸片扩散法因其操作简单和成本低的优点，对临床实验室中细菌的常规药敏试验很有用。美国国家临床实验室标准委员会（NCCLS）推荐的 Kirby-Bauer（KB）法作为纸片扩散试验的标准方法被广泛使用，通过使用折点将微生物简单地分类为对不同抗菌药物敏感、中度敏感、中介或耐药。在确定折点时，显著考虑了最低抑菌浓度（MIC）与临床结果以及药代动力学参数（Cmax、T1/2 和 AUC）之间的关系。然而，不同种族之间存在药代动力学差异，而且日本尚未建立折点。由于折点存在这些问题，在临床实验室向医生报告时，MIC 可能比折点更好。昭和纸片作为一种单纸片法被开发出来，能够从 MIC 与抑菌圈直径之间的线性回归推导出 MIC。因此，认为昭和纸片是日本细菌常规药敏试验的有价值方法之一。有一个问题是，尽管 MIC 的测定方法将转变为微量稀释法，但昭和纸片推导的 MIC 是基于与琼脂稀释法的关系，所以我们使用 110 株革兰氏阳性和革兰氏阴性细菌的挑战集，针对 7 种抗菌药物，比较了昭和纸片法抑菌圈直径推导的 MIC 与肉汤微量稀释法测定的 MIC。在 1 个对数 2 稀释差异内，MIC 的总一致性为 77%，相关系数为 0.929。结果，除了对产β-内酰胺酶阴性的流感嗜血杆菌的四环素和氧氟沙星，以及对大肠杆菌和肺炎克雷伯菌的头孢唑肟的结果外，获得了良好的相关性。
