Shubladze N, Tadumadze N, Bablishvili N
National Centre for Tuberculosis and Lung Diseases, Tbilisi, Georgia.
Int J Mycobacteriol. 2013 Jun 1;2(2):73-78. doi: 10.1016/j.ijmyco.2013.02.002.
Tuberculosis (TB) infections caused by multidrug-resistant (MDR MTB) remain a significant public health concern worldwide. Georgia has a high prevalence of MDR MTB. The genetic mechanisms underlying the emergence of MDR MTB strains in this region are poorly understood and need to be determined for developing better strategies for TB control. This study investigated the frequency of major drug resistance mutations across , and loci of Georgian MDR MTB strains and explored differences between new and previously treated patients. A total of 634 MTB strains were examined for which an MDR phenotype had been previously determined by the proportions method. The system was applied to screen the strains for the presence of (S531L, H526D, H526Y, and D516V), (S315T) and promoter region (C15T and T8C) mutations. The target loci were amplified by PCR and then hybridized with the respective site-specific and wild type (control) probes.
Out of the 634 isolates tested considered by phenotypic testing to be resistant to RIF and INH, this resistance was confirmed by the assay in 575 (90.7%) isolates. RIF resistance was seen in 589 (92.9%) and INH resistance was seen in 584 (92.1%); 67.2% and 84.3% of MDR strains harbored respectively S531L and S315T mutations (generally known as having low or no fitness cost in MTB). The C15T mutation was detected in 22.6% of the strains, whereas H526D, H526Y, D516V and T8C were revealed at a markedly lower frequency (≤5.2%). The specific mutations responsible for the RIF resistance of 110 isolates (17.4%) could not be detected as no corresponding mutant probe was indicated in the assay. There was no specific association of the presence of mutations with the gender/age groups. All types of prevailing mutations had higher levels in new cases. A great majority of the Georgian MDR MTB strains have a strong preference for the drug resistance mutations carrying no or low fitness cost. Thus, it can be suggested that MDR MTB strains with such mutations will continue to arise in Georgia at a high frequency even in the absence of antibiotic pressure.
耐多药结核分枝杆菌（MDR MTB）引起的结核病感染仍是全球重大的公共卫生问题。格鲁吉亚的耐多药结核分枝杆菌患病率很高。该地区耐多药结核分枝杆菌菌株出现的遗传机制了解甚少，需要确定这些机制以便制定更好的结核病控制策略。本研究调查了格鲁吉亚耐多药结核分枝杆菌菌株的katG、rpoB和启动子区域的主要耐药突变频率，并探讨新患者和既往治疗患者之间的差异。共检测了634株结核分枝杆菌菌株，此前已通过比例法确定其为耐多药表型。应用Line probe assay系统筛选菌株中katG（S531L、H526D、H526Y和D516V）、rpoB（S315T）和启动子区域（C15T和T8C）突变的存在情况。通过PCR扩增目标位点，然后与各自的位点特异性和野生型（对照）探针杂交。
在通过表型检测被认为对利福平（RIF）和异烟肼（INH）耐药的634株分离株中，Line probe assay检测确认其中575株（90.7%）耐药。589株（92.9%）出现利福平耐药，584株（92.1%）出现异烟肼耐药；67.2%和84.3%的耐多药菌株分别携带katG S531L和rpoB S315T突变（通常已知在结核分枝杆菌中适应性代价低或无适应性代价）。22.6%的菌株检测到启动子区域C15T突变，而katG H526D、katG H526Y、katG D516V和启动子区域T8C的频率明显较低（≤5.2%）。110株（17.4%）对利福平耐药的分离株中，由于检测中未显示相应的突变探针，因此未检测到导致利福平耐药的特定突变。突变的存在与性别/年龄组无特定关联。所有类型的常见突变在新病例中的水平较高。绝大多数格鲁吉亚耐多药结核分枝杆菌菌株强烈倾向于携带无适应性代价或低适应性代价的耐药突变。因此，可以认为即使在没有抗生素压力的情况下，格鲁吉亚仍会频繁出现携带此类突变的耐多药结核分枝杆菌菌株。
