Bolotin Shelly, Alexander David C, Chedore Pamela, Drews Steven J, Jamieson Frances
Ontario Agency for Health Protection and Promotion, 81 Resources Road, Toronto, Ontario, Canada M9P 3T1.
J Antimicrob Chemother. 2009 Aug;64(2):263-6. doi: 10.1093/jac/dkp183. Epub 2009 Jun 11.
Ontario bears the greatest burden of tuberculosis in Canada, with 40% of all cases and 60% of multidrug-resistant cases. The purpose of this study was to genotypically characterize isoniazid- and rifampicin-resistant isolates and compare these results with phenotypic drug susceptibility testing data. This is the first Canadian study to examine gene mutations that contribute to multidrug-resistant tuberculosis.
A total of 751 tuberculosis isolates were tested for drug resistance using phenotypic antimicrobial susceptibility testing methods. Isolates were then characterized using molecular methods. Following DNA extraction, PCR amplification and sequence analysis were performed on the rifampicin resistance region of rpoB, as well as the region surrounding katG315 and the inhA promoter region associated with isoniazid resistance.
Eighteen different mutation types were found in the rpoB region of rifampicin-resistant isolates. Isolates with mutations at residues rpoB531 (64.1%), rpoB526 (15.2%) and rpoB516 (8.7%) were the most common. In addition, an insertion was found at residue 514. Three phenotypically rifampicin-resistant isolates (3.3%) were genotypically wild-type. In isoniazid-resistant strains, mutations were found most commonly at katG315 (45.4%) as well as at the inhA promoter region (28.6%). Thirty-nine isolates (25.3%) were phenotypically isoniazid-resistant but genotypically wild-type. The katG315 mutation was statistically associated with multidrug-resistant isolates.
This study expands the knowledge of mutations that potentially contribute to drug resistance in tuberculosis and lays the foundation for developing molecular-based tests to determine drug resistance in clinical tuberculosis isolates.
安大略省承担着加拿大结核病的最大负担，占所有病例的40%以及耐多药病例的60%。本研究的目的是对异烟肼和利福平耐药菌株进行基因分型，并将这些结果与表型药敏试验数据进行比较。这是加拿大第一项研究导致耐多药结核病的基因突变。
使用表型抗菌药敏试验方法对总共751株结核分枝杆菌进行耐药性检测。然后使用分子方法对菌株进行特征分析。提取DNA后，对rpoB的利福平耐药区域以及与异烟肼耐药相关的katG315周围区域和inhA启动子区域进行PCR扩增和序列分析。
在利福平耐药菌株的rpoB区域发现了18种不同的突变类型。rpoB531（64.1%）、rpoB526（15.2%）和rpoB516（8.7%）位点发生突变的菌株最为常见。此外，在514位点发现了一个插入。三株表型耐利福平菌株（3.3%）基因分型为野生型。在异烟肼耐药菌株中，最常见的突变发生在katG315（45.4%）以及inhA启动子区域（28.6%）。39株菌株（25.3%）表型耐异烟肼但基因分型为野生型。katG315突变与耐多药菌株在统计学上相关。
本研究扩展了对可能导致结核病耐药的突变的认识，并为开发基于分子的检测方法以确定临床结核分枝杆菌分离株的耐药性奠定了基础。
