Department of Clinical Microbiology and Infectious Diseases, Kalmar County Hospital, 391 85 Kalmar, Sweden; Department of Clinical and Experimental Medicine (IKE), Division of Medical Microbiology, Linköping University, Linköping, Sweden.
Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden; Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden.
Int J Infect Dis. 2017 Feb;55:122-124. doi: 10.1016/j.ijid.2016.12.027. Epub 2017 Jan 6.
Patients with clinical infections caused by the Mycobacterium avium complex (MAC) are treated for at least 1 year following sputum conversion with a regimen that suffers from a suboptimal cure rate. The correlation between clinical outcome and drug susceptibility testing breakpoints other than for the macrolides is regarded to be poor. A systematic evaluation of clinical breakpoints for MAC has not been performed so far; thus, the aim of this study was to initiate the process by establishing minimum inhibitory concentration (MIC) distributions.
The MICs of the major drugs used in the treatment of MAC infections were determined for 229 clinical MAC isolates in cation-adjusted Mueller-Hinton II broth.
The MIC and MIC ranges were established and compared to suggested susceptibility breakpoints for clarithromycin (2; 0.064-128mg/l), rifabutin (0.25; ≤0.25-16mg/l), ethambutol (8; 0.5-32mg/l), amikacin (16; 1-128mg/l), moxifloxacin (2; 0.25-16mg/l), linezolid (32; 1-128mg/l), rifampicin (8; 0.125-16mg/l), and trimethoprim-sulfamethoxazole (2/38; 0.125/2-16/304mg/l).
These results, together with those from available studies, indicate that MICs are high for drugs such as rifabutin, rifampicin, ethambutol, linezolid, and moxifloxacin used against MAC at levels unlikely to be associated with clinical efficacy at current dosing. This may partly explain the poor correlation between susceptibility testing and clinical outcomes for drugs other than clarithromycin.
分枝杆菌复合群（MAC）引起的临床感染患者在痰培养转为阴性后，至少需要接受 1 年的治疗，而这一方案的治愈率并不理想。除大环内酯类药物外，临床疗效与药敏试验折点之间的相关性较差。到目前为止，尚未对 MAC 的临床折点进行系统评价；因此，本研究旨在通过建立最小抑菌浓度（MIC）分布来启动这一过程。
在阳离子调整的 Mueller-Hinton II 肉汤中，对 229 株临床 MAC 分离株进行了主要用于 MAC 感染治疗的药物的 MIC 测定。
确定了 MIC 和 MIC 范围，并与克拉霉素（2；0.064-128mg/l）、利福布汀（0.25；≤0.25-16mg/l）、乙胺丁醇（8；0.5-32mg/l）、阿米卡星（16；1-128mg/l）、莫西沙星（2；0.25-16mg/l）、利奈唑胺（32；1-128mg/l）、利福平（8；0.125-16mg/l）和磺胺甲恶唑（2/38；0.125/2-16/304mg/l）的建议药敏折点进行了比较。
这些结果与现有研究结果一起表明，用于治疗 MAC 的药物（如利福布汀、利福平、乙胺丁醇、利奈唑胺和莫西沙星）的 MIC 较高，而目前的用药剂量不太可能与临床疗效相关。这可能部分解释了除克拉霉素外，药敏试验与临床疗效之间相关性较差的原因。
