Molecular characterization of Mycobacterium tuberculosis isolates from Tehran, Iran by restriction fragment length polymorphism analysis and spoligotyping

Abstract: INTRODUCTION Characterization of Mycobacterium tuberculosis (MTB) isolates by DNA fingerprinting has contributed to tuberculosis (TB) control. The aim of this study was to determine the genetic diversity of MTB isolates from Tehran province in Iran. METHODS MTB isolates from 60 Iranian and 10 Afghan TB patients were fingerprinted by standard IS6110-restriction fragment length polymorphism (RFLP) analysis and spoligotyping. RESULTS The copy number of IS6110 ranged from 10-24 per isolate. The isolates were classified into 22 clusters showing ≥ 80% similarity by RFLP analysis. Fourteen multidrug-resistant (MDR) isolates were grouped into 4 IS6110-RFLP clusters, with 10 isolates [71% (95% CI: 45-89%)] in 1 cluster, suggesting a possible epidemiological linkage. Eighteen Iranian isolates showed ≥ 80% similarity with Afghan isolates. There were no strains with identical fingerprints. Spoligotyping of 70 isolates produced 23 distinct patterns. Sixty (85.7%) isolates were grouped into 13 clusters, while the remaining 10 isolates (14.2%) were not clustered. Ural (formerly Haarlem4) (n = 22, 31.4%) was the most common family followed by Central Asian strain (CAS) (n = 18, 25.7%) and T (n = 9, 12.8%) families. Only 1strain was characterized as having the Beijing genotype. Among 60 Iranian and 10 Afghan MTB isolates, 25% (95% CI: 16-37) and 70% (95% CI: 39-89) were categorized as Ural lineage, respectively. CONCLUSIONS A higher prevalence of Ural family MTB isolates among Afghan patients than among Iranian patients suggests the possible transmission of this lineage following the immigration of Afghans to Iran.

摘要：
引言：采用DNA指纹技术对结核分枝杆菌（Mycobacterium tuberculosis, MTB）分离株进行分型，对结核病（tuberculosis, TB）防控工作具有重要意义。本研究旨在明确伊朗德黑兰省分离的MTB菌株的遗传多样性。
方法：本研究采用标准IS6110限制性片段长度多态性（restriction fragment length polymorphism, RFLP）分析及间隔区寡核苷酸分型（spoligotyping），对60名伊朗籍与10名阿富汗籍结核病患者的MTB分离株进行指纹分型。
结果：所有分离株的IS6110拷贝数介于10~24之间。经RFLP分析，所有分离株可被划分为22个相似度≥80%的聚类群。14株耐多药（multidrug-resistant, MDR）分离株被归入4个IS6110-RFLP聚类群，其中10株分离株（占比71%，95%置信区间：45%~89%）集中于1个聚类群，提示存在潜在的流行病学关联。18株伊朗籍分离株与阿富汗籍分离株的相似度≥80%。未发现指纹图谱完全一致的菌株。对70株分离株进行间隔区寡核苷酸分型后，共获得23种不同的分型模式。其中60株分离株（占比85.7%）被归入13个聚类群，剩余10株（占比14.2%）未被聚类。最常见的家族为乌拉尔谱系（原名为Haarlem4，n=22，占比31.4%），其次为中亚株（Central Asian strain, CAS，n=18，占比25.7%）与T家族（n=9，占比12.8%）。仅1株分离株被鉴定为北京基因型（Beijing genotype）。在60株伊朗籍与10株阿富汗籍MTB分离株中，分别有25%（95%置信区间：16%~37%）与70%（95%置信区间：39%~89%）被归类为乌拉尔谱系。
结论：阿富汗籍患者体内乌拉尔家族MTB分离株的检出率高于伊朗籍患者，提示该谱系可能随着阿富汗移民迁入伊朗而发生了传播。