Sagar T, Singh N P, Kashyap B, Kaur I R
Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, Delhi, India.
J Postgrad Med. 2013 Jul-Sep;59(3):173-6. doi: 10.4103/0022-3859.118031.
Multidrug resistant tuberculosis (MDR-TB) is caused by infection due to Mycobacterium tuberculosis which is resistant to both isoniazid (INH) and rifampicin (RIF). It is caused by selection of resistant mutant strains due to inadequate treatment and poor compliance. MDR-TB is a major public health problem as the treatment is complicated, cure rates are well below those for drug susceptible tuberculosis and patient remains infectious for months despite receiving the best available therapy. The drug susceptibility pattern of M. tuberculosis is essential for proper control of MDR-TB in every health care setting, hence the study was initiated with the aim of studying the prevalence of MDR-TB in patients attending a tertiary care hospital in east Delhi.
Five hundred and forty-three pulmonary and extrapulmonary samples from suspected cases of tuberculosis received in the mycobacteriology laboratory from November 2009 through October 2010 were investigated for M. tuberculosis. All the samples were subjected to direct microscopic examination for demonstration of acid fast bacilli followed by culture on Lowenstein-Jensen (LJ) medium to isolate M. tuberculosis. Identification was done by conventional biochemical methods. Drug susceptibility of isolated M. tuberculosis strains was done by conventional 1% proportion method followed by sequencing of RIF resistant isolates to detect mutations to confirm resistance.
M. tuberculosis was isolated from 75 out of 543 suspected cases of pulmonary/extrapulmonary TB. Three of the total 75 M. tuberculosis isolates (4%) showed resistance to any one of the first line drugs. Prevalence of MDR-TB was 1.3%. The sequencing of single MDR strain showed mutations at codons 516, 517, and 518. Amplification of rpoB and sequential analysis of the amplicon is a better way of detection of mutation and the evidence of new mutation in this study indicate that mutations continue to arise, probably due to the ability of M. tuberculosis to adapt to drug exposure.
耐多药结核病（MDR-TB）是由对异烟肼（INH）和利福平（RIF）均耐药的结核分枝杆菌感染所致。它是由于治疗不充分和依从性差导致耐药突变菌株被选择而引起的。MDR-TB是一个主要的公共卫生问题，因为其治疗复杂，治愈率远低于药物敏感结核病，并且患者尽管接受了最佳可用治疗，但仍会在数月内具有传染性。结核分枝杆菌的药敏模式对于在每个医疗环境中妥善控制MDR-TB至关重要，因此启动了本研究，旨在研究德里东部一家三级医院就诊患者中MDR-TB的患病率。
对2009年11月至2010年10月在分枝杆菌学实验室收到的543份疑似结核病患者的肺和肺外样本进行结核分枝杆菌调查。所有样本均进行直接显微镜检查以显示抗酸杆菌，随后在罗-琴（LJ）培养基上培养以分离结核分枝杆菌。通过传统生化方法进行鉴定。分离出的结核分枝杆菌菌株的药敏试验采用传统的1%比例法，随后对利福平耐药菌株进行测序以检测突变来确认耐药性。
在543例疑似肺/肺外结核病病例中，有75例分离出结核分枝杆菌。75株结核分枝杆菌分离株中有3株（4%）对一线药物中的任何一种耐药。MDR-TB的患病率为1.3%。单个MDR菌株的测序显示密码子516、517和518处发生突变。rpoB基因的扩增和扩增子的序列分析是检测突变的更好方法，本研究中新突变的证据表明突变仍在不断出现，这可能是由于结核分枝杆菌适应药物暴露的能力所致。
