| BackgroundDrug resistance in tuberculosis is a matter of great concern for TB control programs around the world, especially in the clinical treatment of spinal tuberculosis. Detection of drug resistance has been performed by a traditional method based on growth of MTB on L-J Medium. However, due to the low positive rates of this method, the long period of time necessary to obtain results, and more important, the bad biosafety, it is not suitable for clinical application. BACT/ALERT 3D system is able to shorter the time consumption of drug resistance testing , but it still has the shortness of high cost and limited types of drugs which can be tested. Therefore, there is an urgent need to develop a simple, fast and effective method to identify drug resistance in MTB. DNA chip technology,as a new genotypic technology with great efficiency and sensitivity, was developed and used to identify drug-resistance of Mycobacterium tuberculosis. It is necessary to study the feasibility of this new method in clinical application.ObjectiveTo assess the feasibility of DNA chip technology in drug resistance testing, we used DNA chip to detect the mutations associated with drug resistance to isoniazid (INH) and rifampin (RFP) in specimens collected from patients with spinal tuberculosis, and compare its results with a standard which was concluded by use of BACT/ALERT 3D system and absolute concentration drug susceptibility test. This study also provide theoretical basis for designing new DNA chips which can detect more types of anti-tuberculosis drugs simultaneously.MethodsFrom March 2009 to March 2010, 51 paitents with spinal tuberculosis were enrolled into this study. The diagnoses were established by assessment of clinical features, radiological results and history taking. Specimens were collected during surgery from the pus and cheese-like necrotic tissue in spinal lesions. After processed a routine laboratory procedure, the specimens were tested in two ways respectively:1. Inoculate the specimens into vials of the BACT/ALERT 3D system, and then perform the drug susceptibility test in specimens which tested positive by BACT/ALERT 3D system using absolute concentration drug susceptibility test.2. Strain identification and drug resistance testing using DNA chip.Assess the applicability of DNA chip technology in drug resistance in clinical application by compare its results with a standard which was concluded by use of BACT/ALERT 3D system and absolute concentration drug susceptibility test.Result1. BACT/ALERT 3D system culture and absolute concentration drug susceptibility test.The positive rate of MTB culture is 52.9% (27/51). The drug susceptibility testing showed a total drug resistance rate of 25.9% (7/27). The average detection time was 42d (ranged from 28～58d).2. Strain identification and drug resistance testing by using DNA chipThe positive rate of strain identification of MTB using DNA chip is 82.4% (42/51). Both sensitivity and specificity are 100% in INH resistance testing by DNA chip technology, Analogously,sensitivity and specificity in RFP resistance testing are 100% and 91.7%. The average detection time was 20h ( ranged from 18～23h).Conclusion1. The traditional method of drug resistance testing in tuberculosis based on growth of MTB on L-J Medium had a low positive rate, a long period of time to obtain results and bad biosafety. Obviously, it is not suitable for clinical application.2. Compared with traditional method, there are many advantages to adopt DNA chip technology for MTB drug resistance test, such as less time consumption, satisfactory positive detection rate, high sensitivity and specificity and good biosafety, so it is suitable for clinical application. 3. Currently, the DNA chip technology can only detect resitance of two kinds of anti-tuberculosis drugs, so the DNA chip which can detect more anti-tuberculosis drugs is urgently needed.
|
PDF Full Text Request