AmpliSensor—聚合酶链反应定量检测肺结核患者外周血结 …

目的 探讨ＡｍｐｌｉＳｅｎｓｏｒ－聚合酶链反应定量检测外周血中结核分支杆菌ＤＮＡ在肺结核的应用价值。方法 采用ＱｌＡａｍｐ和ＡｃｕＰｕｒｅ法提取，制备全血中模板ＴＢ－ＤＮＡ，应用ＡｍｐｌｉＳｅｎｓｏｒ－ＰＣＲ定量检测，并与ＩＳ６１１０－单管巢式聚合酶链反应（ＳＮ－ＰＣＲ）作比较。结果２００例肺结核患者的血液标本中，两种方法测得结核分支杆菌ＤＮＡ的阳性率分别为６０．５％、６３．５％。８５例非结核肺病     

Detection of Mycobacterium tuberculosis in bronchoalveolar lavage from patients with sputum smear-negative pulmonary tuberculosis using a polymerase chain reaction assay

Abstract The objective of this study was to evaluate the utility of a polymerase chain reaction (PCR) assay in detecting Mycobacterium tuberculosis in bronchoalveolar lavage (BAL) specimens of patients suspected of having active pulmonary tuberculosis (TB) but who were sputum smear-negative. Patients undergoing investigation for suspected pulmonary TB at the University Hospital, Kuala Lumpur, and who were sputum smear-negative underwent fibreoptic bronchoscopy and BAL. One portion of each lavage specimen was submitted for smear examination for acid-fast bacilli and mycobacterial culture and the other portion assayed by PCR for the presence of a 562-base pair DNA segment belonging to the insertion sequence IS986, unique to the M. tuberculosis complex. As controls, lavage specimens from patients with other lung lesions were also similarly tested. The PCR assay gave a positivity rate of 80.9% (55 of 68) compared with 8.8% of smear examination and 7.4% of culture for detecting M. tuberculosis in BAL specimens. The assay was positive in two of 45 BAL specimens from 35 control subjects. The PCR assay was more sensitive than smear and culture in detecting M. tuberculosis in BAL specimens of patients with sputum smear-negative pulmonary TB.     

The IS6110 repetitive DNA element of Mycobacterium tuberculosis is not detected in exhaled breath condensate of patients with active pulmonary tuberculosis

BACKGROUND: A large tertiary referral hospital in inner-city Chicago. OBJECTIVES: To determine whether the IS6110 repetitive DNA element of Mycobacterium tuberculosis is detected in exhaled breath condensate of patients with newly diagnosed active pulmonary tuberculosis. METHODS: Ten hospitalized patients with positive Ziehl-Neelson-stained sputum smears were studied. Concurrent sputum cultures for mycobacteria were performed as well. Exhaled breath condensate was collected from each patient within 6 days of initiating antituberculosis chemotherapy (median 1.5 days). These samples were analyzed by polymerase chain reaction (PCR) using primers designed to amplify the IS6110 DNA fragment of M. tuberculosis. Exogenous M. tuberculosis DNA was added to exhaled breath condensate samples to detect PCR inhibitors. Concurrent cultures of exhaled breath condensate for mycobacteria were performed. RESULTS:M. tuberculosis was identified in 9 of 10 sputum cultures. One isolate was identified as Mycobacterium kansasii. The IS6110 repetitive DNA element of M. tuberculosis was not detected in any of the 10 exhaled breath condensate samples. Exogenous M. tuberculosis DNA added to these samples elicited the characteristic band pattern of M. tuberculosis on agarose gel electrophoresis. No PCR inhibitors were detected. Cultures of exhaled breath condensate showed no growth of mycobacteria. CONCLUSIONS: The IS6110 repetitive DNA element of M. tuberculosis is not detected in exhaled breath condensate of patients with newly diagnosed active pulmonary tuberculosis.     

Evaluation of PCR-based methods for the diagnosis of tuberculosis by identification of mycobacterial DNA in urine samples.

SETTING: The Chest Clinic and the JICA (Japan International Cooperation Agency) Molecular Laboratories, University Teaching Hospital, Lusaka, Zambia, and the Department of Internal Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan. OBJECTIVE: To evaluate the polymerase chain reaction (PCR) as a laboratory test for the rapid diagnosis of pulmonary tuberculosis in the African situation by identifying mycobacterial DNA in urine samples using two commonly described molecular methods. DESIGN: Prospective collection and laboratory analysis of urine samples from adult Zambian patients with culture-confirmed pulmonary tuberculosis and healthy controls. METHODS: Urine was obtained from 63 patients with culture-confirmed active pulmonary tuberculosis and 63 'healthy' control patients with no active tuberculosis. DNA was isolated from urine sediment and subjected to analyses by two well-described PCR-based methods, 'the Sechi method' and 'the Githui method', for the identification of Mycobacterium tuberculosis DNA. The sensitivity and specificity of the two tests were determined. RESULTS: The sensitivity and specificity of the Githui method were 55.6% (35/63) and 98.4% (62/63), respectively. The sensitivity and specificity of the Sechi method were 28.6% (18/63) and 98.4% (62/63), respectively. Of the 63 patients, 50 (79%) were HIV sero-positive and the frequency of positive PCR urines using the Githui method was greater in HIV-positive patients than in HIV-negative patients (32/50 = 64% vs. 3/13 = 23%; P = 0.05). CONCLUSIONS: Neither the Githui method nor the Sechi method was sensitive enough to be recommended for routine use in clinical practice. PCR-based assays for the detection of M. tuberculosis DNA in urine will require further refinement before they can be recommended for use in clinical practice in Africa. The presence of mycobacterial DNA in urine samples of patients with pulmonary tuberculosis also requires further study.     

应用磁纳米捕获-PCR技术检测痰液结核分枝杆菌的研究

目的采用磁纳米捕获技术富集痰液中的结核分枝杆菌,以提高PCR检测的灵敏度,快速诊断结核病。方法以普通PCR为对照,采用磁纳米捕获技术富集187份结核和非结核呼吸系统疾病患者痰标本中的结核分枝杆菌,进行PCR检测。结果 152份肺结核患者痰标本41份(27.0%)涂片抗酸染色阳性,72份(47.4%)普通PCR检测阳性,126份(82.9%)磁纳米捕获-PCR检测阳性。35份非结核呼吸系统疾病患者,痰标本中抗酸染色均为阴性,1份普通PCR和磁纳米捕获-PCR检测均阳性,该患者临床诊断肺部感染合并陈旧性肺结核。结论采用磁纳米捕获技术富集痰液中的结核分枝杆菌,可显著提高PCR检测的灵敏度。     

聚合酶链反应DNA扩增对活动性肺结核的诊断价值

为探讨聚合酶链反应(PCR)DNA扩增对诊断活动性肺结核的临床价值,本文用PCR技术扩增结核杆菌特有的MPB64蛋白基因序列,对121例病人临床标本进行检测。发现34例活动性肺结核中有28例PCR阳性;疑诊为肺结核者33例中有18例阳性;非结核肺疾患54例中有10例阳性,其中有肺结核既往史者阳性6例,有结核接触史者阳性3例。提示PCR阳性并非为活动性肺结核所特有。     

Cytokine responses induced by Mycobacterium tuberculosis in patients with HIV-1 infection and tuberculosis.

OBJECTIVE: Tuberculosis (TB) is an important opportunistic infection in HIV patients. Immune responses to Mycobacterium tuberculosis in HIV/TB patients were evaluated. METHODS: Fifteen patients with HIV/TB, ten with HIV, four with TB, and five controls were enrolled. Peripheral blood mononuclear cells were isolated and stimulated with mycobacterial antigen (PPD). Interferon (IFN)-gamma and TNF-alpha in culture supernatants were measured by ELISA. RESULTS: IFN-gamma and TNF-alpha production after PPD stimulation was markedly decreased in HIV patients, but not in HIV/TB patients. In HIV patients with a CD4 cell count of less than 200/mm3, IFN-gamma and TNF-alpha production after PPD stimulation was higher in HIV/TB patients than in HIV patients. Cytokine responses to M. tuberculosis reconstituted after highly active antiretroviral therapy (HAART) and were prominent in HIV/TB patients. CONCLUSIONS: Cytokine responses to M. tuberculosis were retained in HIV-infected patients with tuberculosis, even in patients with a CD4 cell count of less than 200/mm3, and reconstituted after HAART.     

荧光定量PCR测定支气管肺泡灌洗液中TbDNA对涂阴肺结核的诊断价值

目的探讨纤支镜肺泡灌洗液中结核分枝杆菌DNA在涂阴肺结核诊断中的价值。方法应用荧光定量聚合酶链反应（FQ-PCR）技术对300例涂阴肺结核,178例菌阳肺结核及119例肺炎或肺癌患者的纤支镜肺泡灌洗液标本进行结核分枝杆菌DNA检测。结果3种病因肺泡灌洗液结核分枝杆菌DNA阳性检出率分别为：74.3%（223/300）、94.9%（169/178）、17.6%（21/119）。结论荧光定量聚合酶链反应检测肺泡灌洗液结核分枝杆菌DNA,用于肺结核诊断可提高肺结核诊断的敏感性和准确性,明显优于痰抗酸染色,亦较痰结核菌培养诊断灵敏、快速,可作为肺结核诊断较可靠指标。     

Method for efficient storage and transportation of sputum specimens for molecular testing of tuberculosis.

SETTING: The polymerase chain reaction (PCR) is a highly sensitive method for the detection of Mycobacterium tuberculosis and is available in most countries, though to a lesser extent in rural areas. OBJECTIVE: To amplify M. tuberculosis DNA sequences of sputum spotted on FTA cards and compare them with the results of microscopic examination among culture-positive samples. DESIGN: A total of 102 sputum specimens of TB patients in treatment were spotted on FTA cards and stored at room temperature until DNA analysis. We assessed the IS6110 region of M. tuberculosis. The efficacy of the PCR assay for the direct detection of M. tuberculosis was evaluated and compared with the results of cultures (Middlebrook 7H9 broth) and smears of fresh sputum specimens. RESULTS: We were able to detect 10 fg/microl of mycobacterial DNA even after 6 months in storage. The PCR sensitivity and specificity using the FTA card system were 82% and 96%, while microscopic examination showed 41% and 95%, respectively. CONCLUSION: The FTA card system for the storage of bacterial DNA from sputum samples should be considered for the molecular diagnosis of tuberculosis. Samples can easily be obtained from geographically isolated populations and shipped by mail for accurate molecular diagnosis.     

西安市结核病的病原学调查

目的调查西安市结核病的分枝杆菌菌种类型及其分布。方法采用抽样调查方法收集结核病患者的痰标本及其背景资料,用痰涂片、痰培养以及PCR方法检测,用鉴别培养基对分离菌株进行菌种鉴定。结果共收集574例拟诊结核病病例,实验室检测1602份痰标本。采用痰涂片、痰培养和PCR3种方法联合应用,阳性者260例,分枝杆菌检测阳性率45.30。137例分枝杆菌培养阳性者中,结核分枝杆菌复合体占73.72,其中结核分枝杆菌和牛分枝杆菌分别为67.88和5.84;11.68为非结核分枝杆菌,14.60为混合感染,其中11.68为结核分枝杆菌与牛分枝杆菌,2.92为结核分枝杆菌与非结核分枝杆菌混合感染。结论西安市结核病的致病菌复杂,包括结核分枝杆菌、牛分枝杆菌和非结核分枝杆菌,尤其是非结核分枝杆菌混合感染应予以高度重视。     

Evaluation of the Idaho Technology LightCycler PCR for the direct detection of Mycobacterium tuberculosis in respiratory specimens.

SETTING: The rapid detection of Mycobacterium tuberculosis (TB) in clinical samples is an important goal. The LightCycler heralds an advance in thermal cycle technology combining rapid cycle DNA amplification with fluorimetry, eliminating the need to perform amplification and product analysis separately. OBJECTIVES: To evaluate the LightCycler for direct detection of M. tuberculosis complex in respiratory specimens. To evaluate a DNA extraction method based on Chelex 100 resin, heating and ultrasonication for the prevention of endogenous inhibitions in respiratory samples. DESIGN: DNA was extracted from sputum samples using the Chelex method and polymerase chain reaction (PCR) for TB performed with the LightCycler. RESULTS: For 88 sputum samples positive by microscopy and culture for M. tuberculosis, 95% were PCR-positive. None of the five sputum samples that were smear-negative but culture-positive for M. tuberculosis, the 79 culture-negative sputum samples and the 29 sputum samples that were culture-positive for mycobacteria other than TB yielded positive PCR results. PCR inhibitors were not detected in any of the samples. CONCLUSION: The LightCycler proved a simple, reproducible and rapid system, reducing the time to result from weeks (culture) or days (conventional PCR) to hours. The Chelex 100 resin method produced good results for the smear-positive specimens. However, a larger study is required to determine the efficacy of the method with smear-negative specimens and for specimens known to contain endogenous inhibitors.     

Combined use of serum and urinary antibody for diagnosis of tuberculosis

Efforts to devise immunoassays for tuberculosis (TB) that can be adapted to rapid formats are ongoing. The present study was aimed at determining whether urinary anti-Mycobacterium tuberculosis antibodies are present in patients with TB, to evaluate the feasibility of developing a urine antibody-based diagnostic test. Urinary antibodies directed against the culture filtrate proteins of M. tuberculosis, MPT 32, and the 81-kDa GlcB protein were detectable in patients with TB, although the sensitivity of antibody detection was lower (53%-64%), compared with serum antibodies (68%-77%). Surprisingly, with all 3 antigens, the use of paired serum and urine samples provided higher sensitivities of antibody detection than either single specimen, and anti-GlcB antibodies were present in the serum and/or urine of 39 (90%) of 43 smear-positive patients with TB. Although, with the current methods and antigens, the level of sensitivity is insufficient to design a urinary antibody diagnostic test, these studies provide the foundation for further studies on the development of a urine antibody-based immunoassay for TB.     

Rapid and direct detection of Mycobacterium tuberculosis complex and mycobacteria in sputum by advanced method, PCR]

We developed two PCR methods, which amplify bovine tuberculous MPB70 gene and mycobacterial 16S rRNA gene, for detection of tubercle bacilli and mycobacteria in sputum, respectively. Among 27 Mycobacterium species and 57 species of 30 genuses other than Mycobacterium, only M. tuberculosis (TB) complex, i.e., M. tuberculosis, M. bovis, M. africanum, M. microti showed DNA amplification by PCR for MPB70, and amplification of 16S rRNA gene were observed specific in Mycobacterium species. A combination of these PCR abilities were available to differentiate the TB complex and nontuberculous mycobacteria (NTM). We investigated the correlation between these methods and conventional methods with 311 sputa that were suspected mycobacteriosis. The PCR method could detect 12 cases of TB complex and 4 cases of NTM in 17 specimens, which were positive by conventional methods, but could not for one specimen. Among 294 specimens that were negative with conventional methods, the PCR method detected 13 and 8 cases of TB complex and NTM, respectively. These results were confirmed by commercial tuberculous specific DNA probe or investigation of the clinical background of the patients. On the other hand, 273 specimens showed negative result either PCR nor conventional methods. The PCR method did not detect tuberculous DNA in normal 197 sputa, which were not suspected mycobacteriosis. These results indicate that each one of these PCR methods is highly specific to TB complex or Mycobacterium species. We concluded that these PCR methods are useful and advanced methods for rapid and direct detection of tuberculosis and mycobacteriosis.     

Detection of Neisseria gonorrhoeae in first-voided urine sediments from male urethritis patients by polymerase chain reaction]

Neisseria gonorrhoeae was detected from first-voided urine sediments of male patients with urethritis by polymerase chain reaction (PCR). Urine and urinary sediment were treated with proteinase K, and DNA was further purified by phenol extraction. Two oligonucleotides based on sequences within a ribosomal RNA gene from N. gonorrhoeae were used as primers for the PCR. A DNA fragment of 206 bp specific for N. gonorrhoeae was amplified by PCR and detected by agarose gel electrophoresis. In 19 specimens of urine sediments collected from 21 patients in whom N. gonorrhoeae was isolated from urethral swab by culture, 206 bp DNA fragment was amplified by PCR. In all specimens of urine sediments from 24 patients in whom cultures for N. gonorrhoeae were negative, no DNA was amplified by the PCR. The overall coincidence rate between the PCR for detecting N. gonorrhoeae in first-voided urine sediments and culture in urethral swab was 95.6% (43/45). PCR procedure for detection of pathogens from first-voided urine sediments would be noninvasive and would be applied for the diagnosis of gonococcal urethritis and chlamydial urethritis.     

Detection of Mycobacterium tuberculosis in sputum samples using a polymerase chain reaction

A polymerase chain reaction (PCR) assay for the rapid detection of Mycobacterium tuberculosis in sputum samples is described. The target DNA is a 123-base pair (bp) segment of IS6110, which is repeated in the M. tuberculosis chromosome and is specific for the M. tuberculosis complex. Methodology used to lyse the mycobacteria, extract the DNA, and amplify the 123-bp target DNA is presented. The amplified PCR product is detected by examination of ethidium-bromide-stained acrylamide gels. An internal control using the same primers as the target DNA has been constructed to assess the efficacy of each individual reaction. Of 162 sputum samples tested, 82 were smear-positive for acid-fast bacilli. Of the 94 specimens from patients in whom pulmonary tuberculosis was diagnosed, 51 were culture-positive, smear-positive, or both. Fifty of these were PCR positive. Of the 42 specimens from patients with nontuberculous mycobacterial pulmonary disease, 41 were PCR negative. All 26 specimens from patients without mycobacterial infection were PCR negative. This assay provides a sensitive and specific means for the laboratory diagnosis of tuberculosis within 48 h that is relatively simple to perform.     

Diagnosis of intestinal tuberculosis using a monoclonal antibody to Mycobacterium tuberculosis

AIM: To investigate the utility of immunohistochemical (IHC) staining with an antibody to Mycobacterium tuberculosis (M. tuberculosis) for the diagnosis of intestinal tuberculosis (TB).METHODS: We retrospectively identified 10 patients (4 males and 6 females; mean age = 65.1 ± 13.6 years) with intestinal TB. Clinical characteristics, including age, gender, underlying disease, and symptoms were obtained. Chest radiograph and laboratory tests, including sputum Ziehl-Neelsen (ZN) staining, M. tuberculosis culture, and sputum polymerase chain reaction (PCR) for tubercle bacilli DNA, as well as Tuberculin skin test (TST) and QuantiFERON-TB gold test (QFT), were examined. Colonoscopic records recorded on the basis of Sato’s classification were also reviewed, in addition to data from intestinal biopsies examined for histopathological findings, including hematoxylin and eosin staining, and ZN staining, as well as M. tuberculosis culture, and PCR for tubercle bacilli DNA. For the present study, archived formalin-fixed paraffin-embedded (FFPE) intestinal tissue samples were immunohistochemically stained using a commercially available species-specific monoclonal antibody to the 38-kDa antigen of the M. tuberculosis complex. These sections were also stained with the pan-macrophage marker CD68 antibody.RESULTS: From the clinical data, we found that no patients were immunocompromised, and that the main symptoms were diarrhea and weight loss. Three patients displayed active pulmonary TB, six patients (60%) had a positive TST, and 4 patients (40%) had a positive QFT. Colonoscopic findings revealed that all patients had type 1 findings (linear ulcers in a circumferential arrangement or linear ulcers arranged circumferentially with mucosa showing multiple nodules), all of which were located in the right hemicolon and/or terminal ileum. Seven patients (70%) had concomitant healed lesions in the ileocecal area. No acid-fast bacilli were detected with ZN staining of the intestinal tissue samples, and both M. tuberculosis culture and PCR for tubercle bacilli DNA were negative in all samples. The histopathological data revealed that tuberculous granulomas were present in 4 cases (40%). IHC staining in archived FFPE samples with anti-M. tuberculosis monoclonal antibody revealed positive findings in 4 patients (40%); the same patients in which granulomas were detected by hematoxylin and eosin staining. M. tuberculosis antigens were found to be mostly intracellular, granular in pattern, and primarily located in the CD68⁺ macrophages of the granulomas.CONCLUSION: IHC staining with a monoclonal antibody to M. tuberculosis may be an efficient and simple diagnostic tool in addition to classic examination methods for the diagnosis of intestinal TB.     

Detection of Chlamydia trachomatis in first-voided urine sediments from male urethritis by polymerase chain reaction]

Chlamydia trachomatis was detected from first-voided urine sediments of 97 male patients with urethritis by polymerase chain reaction (PCR). Since urine and urinary sediments only treated with proteinase K inhibited DNA amplification by PCR, DNA was further purified by phenol extraction and concentrated. Two oligonucleotides based on sequences within the major outer membrane gene from C. trachomatis serovar L2 were used as primers. A DNA fragment of 242 bp specific for C. trachomatis was amplified by PCR and detected by agarose gel electrophoresis. The DNA fragment was amplified by PCR in all specimens of urine sediments from 50 patients with Chlamydiazyme-positive urethral swab. In 38 specimens of urine sediments from 47 patients with Chlamydiazyme-negative urethral swab, PCR was negative. The overall coincidence rate between the PCR for detecting C. trachomatis in first-voided urine sediments and Clamydiazyme in urethral swab was 90.7% (88/97). Detection of C. trachomatis from first-voided urine sediments by PCR was considered to be noninvasive and useful for the diagnosis of male urethritis due to C. trachomatis.     

Influence of HLA-DR antigens on lymphocyte response to Mycobacterium tuberculosis culture filtrate antigens and mitogens in pulmonary tuberculosis.

SETTING: Influence of HLA-DR antigens and lymphocyte responses in pulmonary TB patients. OBJECTIVE: To elucidate the role of HLA-DR genes/gene products on lymphocyte responses to Mycobacterium tuberculosis antigens and mitogens, the present study was carried out in pulmonary tuberculosis during active and cured stage of the disease. DESIGN: Serological determination of HLA-DR antigens was carried out in 50 active TB patients, 44 cured TB patients and 58 normal healthy control subjects. The influence of HLA-DR antigens on peripheral blood lymphocyte responses to M. tuberculosis culture filtrate antigens and mitogens such as phytohaemagglutinin (PHA) and concanavalin-A (Con-A) was studied in the patients as well as normal healthy control subjects. RESULTS: Of all the DR antigens studied, patients (active TB and cured TB) with DR2 antigen showed an increased lymphocyte response (stimulation index) to a higher dose of antigenic (10 micrograms/ml) stimulation. A significantly lower lymphocyte response to antigen and mitogens was seen in HLA-DR3 positive normal healthy subjects than non-DR3 (DR3 negative) subjects. CONCLUSION: The present study suggests that HLA-DR genes/gene products may be playing an immunoregulatory role in eliciting an immune response against M. tuberculosis antigens and mitogens induced lymphocyte response in pulmonary TB patients and normal healthy subjects.     

Recurrent tuberculosis in Houston, Texas: a population-based study.

OBJECTIVE: To determine the predictors of recurrence of tuberculosis (TB), the drug resistance pattern of Mycobacterium tuberculosis strains recovered from recurrent TB patients, and the frequency of re-infection with a new M. tuberculosis strain among patients with recurrent disease. DESIGN: A population-based, retrospective case-control study using the Houston Tuberculosis Initiative database. RESULTS: We found that, among 100 patients with recurrent TB who completed adequate therapy for a first episode of TB, not receiving directly observed therapy, pulmonary disease, HIV/AIDS diagnosis, not having a family physician, being unemployed and using public transportation were predictors of recurrent disease. There was a significant increase in drug-resistant M. tuberculosis strains in the second episode of disease compared to the first episode (21.3% vs. 8.2%, P = 0.04). Exogenous re-infection with a new strain of M. tuberculosis was found to cause 24-31% of recurrent TB. CONCLUSION: Recurrent TB in Houston is associated with a significant increase in drug-resistant M. tuberculosis strains. Re-infection with a new M. tuberculosis strain causes a significant proportion of recurrent TB in an area of low TB incidence. Patients with HIV/AIDS constitute a population at increased risk of disease recurrence.     

Comparative assays of the rpoB gene for identification of Mycobacterium tuberculosis isolated from patients in Sudan.

OBJECTIVES: To characterise mycobacterial clinical isolates based on amplification of the rpoB gene. SETTING: One hundred and thirty-five mycobacterial isolates cultured from suspected pulmonary tuberculosis (TB) patients were identified phenotypically. Molecular characterisation of the isolates was performed based on amplification of the rpoB gene, using duplex polymerase chain reaction (DPCR), PCR-restriction fragment length polymorphism (RFLP) and nested PCR-based sequence analysis techniques. RESULTS: The DPCR assay identified 129 of 135 (95.5%) clinical isolates as Mycobacterium tuberculosis complex species. Restriction enzyme analysis of the rpoB PCR product using Hind II identified 134 of the 135 (99.3%) isolates as M. tuberculosis complex, while nested PCR sequence analysis of the rpoB gene identified 133/133 examined isolates (100%) as M. tuberculosis species. No mycobacteria other than M. tuberculosis (MOTT) were detected among the studied isolates. CONCLUSION: DPCR, PCR/RFLP Hind II and nested PCR sequence analysis of the rpoB gene techniques showed comparable efficiency in the characterisation of Mycobacterium isolates. Nested PCR sequence analysis of the rpoB gene was superior to PCR/RFLP for characterisation of suspected M. tuberculosis isolates, while the DPCR technique showed less sensitivity. As PCR-RFLP requires less sophisticated laboratory facilities than nested PCR sequence analysis, it would be more appropriate to be adopted for accurate characterisation of mycobacteria in countries with a weak infrastructure.