Musa Humberto R, Ambroggi Marta, Souto Alejandro, Angeby K A Kristian
Laboratorio de Micobacteriología, Hospital F. J. Muñiz, Buenos Aires, Argentina.
J Clin Microbiol. 2005 Jul;43(7):3159-61. doi: 10.1128/JCM.43.7.3159-3161.2005.
Current methods for drug susceptibility testing of Mycobacterium tuberculosis are either costly or slow. As the prevalence of multidrug-resistant strains increases, the need for fast, reliable, and inexpensive methods that can also be applied in settings with scarce resources is obvious. We evaluated a rapid colorimetric nitrate reductase assay (NRA) for direct drug susceptibility testing of M. tuberculosis directly from clinical sputum samples with positive microscopy results for acid-fast bacilli with more than 10 acid-fast bacilli per high-power field. We have saved valuable time by omitting the preisolation step. The sensitivity (ability to detect true drug resistance) and specificity (ability to detect true drug susceptibility) of the direct NRA, using the direct proportion method as the reference, were 100 and 100%, 93 and 100%, 76 and 100%, and 55 and 99% for rifampin, isoniazid, streptomycin, and ethambutol, respectively, when tested on M. tuberculosis strains present in 121 samples. The results were in most cases available in 14 days. The direct NRA could be used as a rapid, inexpensive, and accurate method to determine rifampin and isoniazid susceptibility directly from sputum. The technique might become a valid alternative to traditional methods, especially in low-income countries.
目前用于结核分枝杆菌药敏试验的方法要么成本高昂，要么速度缓慢。随着耐多药菌株的流行率增加，显然需要能够在资源匮乏环境中应用的快速、可靠且廉价的方法。我们评估了一种快速比色硝酸还原酶试验（NRA），用于直接从临床痰标本中对结核分枝杆菌进行药敏试验，这些痰标本经显微镜检查显示抗酸杆菌阳性，每高倍视野有超过10条抗酸杆菌。我们通过省略预分离步骤节省了宝贵的时间。以直接比例法为参考，直接NRA对利福平、异烟肼、链霉素和乙胺丁醇的敏感性（检测真正耐药性的能力）和特异性（检测真正药敏性的能力），在对121份样本中存在的结核分枝杆菌菌株进行测试时，分别为100%和100%、93%和100%、76%和100%、55%和99%。大多数情况下，结果在14天内可得。直接NRA可作为一种快速、廉价且准确的方法，直接从痰液中确定利福平和异烟肼的药敏性。该技术可能成为传统方法的有效替代方法，尤其是在低收入国家。
