Brown-Elliott Barbara A, Hanson Kimberly, Vasireddy Sruthi, Iakhiaeva Elena, Nash Kevin A, Vasireddy Ravikiran, Parodi Nicholas, Smith Terry, Gee Martha, Strong Anita, Barker Adam, Cohen Samuel, Muir Haleina, Slechta E Susan, Wallace Richard J
Mycobacteria/Nocardia Laboratory, The University of Texas Health Science Center at Tyler, Tyler, Texas, USA
Pathology Laboratories, A.R.U.P., Salt Lake City, Utah, USA.
J Clin Microbiol. 2015 Mar;53(3):875-8. doi: 10.1128/JCM.02936-14. Epub 2015 Jan 7.
Macrolide resistance has been linked to the presence of a functional erythromycin ribosomal methylase (erm) gene in most species of pathogenic rapidly growing mycobacteria (RGM). For these Mycobacterium isolates, extended incubation in clarithromycin is necessary to determine macrolide susceptibility. In contrast, the absence of a detectable erm gene in isolates of M. chelonae, M. senegalense, and M. peregrinum and a nonfunctional erm gene in M. abscessus subsp. massiliense and 15% to 20% of M. abscessus subsp. abscessus isolates renders these species intrinsically macrolide susceptible. Not all RGM species have been screened for the presence of an erm gene, including the Mycobacterium mucogenicum group (M. mucogenicum, M. phocaicum, and M. aubagnense) and Mycobacterium immunogenum. A total of 356 isolates of these two pathogenic RGM taxa from two reference laboratories (A.R.U.P. Reference Laboratories and the Mycobacteria/Nocardia Laboratory at the University of Texas Health Science Center at Tyler) underwent clarithromycin susceptibility testing with readings at 3 to 5 days and 14 days. Only 13 of the 356 isolates had resistant clarithromycin MICs at initial extended MIC readings, and repeat values on all available isolates were ≤2 μg/ml. These studies suggest that these two additional RGM groups do not harbor functional erm genes and, like M. chelonae, do not require extended clarithromycin susceptibility testing. We propose to the Clinical Laboratory and Standards Institute that isolates belonging to these above-mentioned six rapidly growing mycobacterial groups based on molecular identification with no known functional erm genes undergo only 3 to 5 days of susceptibility testing (to exclude mutational resistance).
在大多数致病性快速生长分枝杆菌（RGM）物种中，大环内酯类耐药性与功能性红霉素核糖体甲基化酶（erm）基因的存在有关。对于这些分枝杆菌分离株，需要在克拉霉素中延长培养时间以确定大环内酯类药物敏感性。相比之下，在龟分枝杆菌、塞内加尔分枝杆菌和偶发分枝杆菌的分离株中未检测到erm基因，而脓肿分枝杆菌马赛亚种和15%至20%的脓肿分枝杆菌脓肿亚种分离株中的erm基因无功能，这使得这些菌种本质上对大环内酯类药物敏感。并非所有RGM物种都进行了erm基因筛查，包括产黏液分枝杆菌组（产黏液分枝杆菌、海豹分枝杆菌和奥巴涅分枝杆菌）和免疫分枝杆菌。来自两个参考实验室（A.R.U.P.参考实验室和德克萨斯大学泰勒健康科学中心的分枝杆菌/诺卡氏菌实验室）的这两种致病性RGM分类群的356株分离株进行了克拉霉素敏感性测试，分别在3至5天和14天读取结果。在最初的延长MIC读数中，356株分离株中只有13株克拉霉素MIC耐药，所有可用分离株的重复值均≤2μg/ml。这些研究表明，这两个额外的RGM组不含有功能性erm基因，并且像龟分枝杆菌一样，不需要延长克拉霉素敏感性测试。我们向临床实验室和标准协会提议，基于分子鉴定属于上述六个快速生长分枝杆菌组且无已知功能性erm基因的分离株仅进行3至5天的敏感性测试（以排除突变耐药性）。
