Evaluation of a polymerase chain reaction for the diagnosis of tuberculosis

Diagnosis and Management of Occult Cervical Tuberculous Lymphadenopathy

Objective: Some cervical tuberculous lymphadenopathy (CTL) presents no evidence of tuberculosis (TB), even after thorough examination of a fine-needle aspiration (FNA) specimen. After the examination of excisional specimens, when the polymerase chain reaction (PCR) analysis identifies the nucleic acid of Mycobacterium tuberculosis (Mtb) or the culture results are positive, then the diagnosis of CTL is established. We refer to this condition as occult CTL (OCTL). Patient and Methods: The present work is a retrospective review of a consecutive series of OCTL cases that were treated at the Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, between June 2015 and September 2020. When the diagnosis of OCTL was established, the patients received the standard anti-TB chemotherapy. Results: Fourteen cases of OCTL, including 9 female and 5 male patients, aged 24 to 71 years (median age 42 years), were included in the present study. The most commonly observed levels of lymph node involvement were level V and level II. Each level of the involved lymph nodes was removed entirely through en bloc surgical resection. An evaluation of the excisional specimens led to positive PCR results in all 14 cases, with 2 cases presenting positive culture and 3 cases exhibiting positive acid-fast bacilli (AFB) staining. Recovery was uneventful, and the anti-TB chemotherapy was completed in all cases. The median duration of follow-up was 29 months, during which no case of TB relapse was observed. Conclusions: Wide surgical excision is crucial for the diagnosis and management of OCTL, and when used in combination with anti-TB chemotherapy, it results in satisfactory patient outcomes.

Bacteriologically confirmed extra pulmonary tuberculosis and treatment outcome of patients consulted and treated under program conditions in the littoral region of Cameroon

BACKGROUND

Extra-pulmonary tuberculosis (EPTB) is defined as any bacteriologically confirmed or clinically diagnosed case of TB involving organs other than the lungs. It is frequently a diagnostic and therapeutic challenge with paucity of data available. The aim of this study was to assess the prevalence of bacteriologically confirmed EPTB; to determine the most affected organs and to evaluate the therapeutic outcome of EPTB patients treated under program conditions in the littoral region of Cameroon.

METHODS

A descriptive cross-sectional laboratory-based epidemiological survey was conducted from January 2016 to December 2017 and 109 specimens from 15 of the 39 diagnosis and treatment centers in the littoral region were obtained. Two diagnostic methods (Gene Xpert MTB and culture (LJ and MGIT) were used for EPTB diagnosis. Determine HIV1/2 and SD Biolinewere used for HIV diagnosis. Confirmed EPTB cases were treated following the national tuberculosis guide.

RESULTS

The prevalence of bacteriologically confirmed EPTB was 41.3% (45). All 45 cases were sensitive to rifampicin. Males were predominately more infected [26 (57.8%)] likewise the age group 31-45 years with 15 (33.3%) cases. The overall prevalence for HIV was 33.6% (36). HIV infection was present in 28.9% (13) of patients with EPTB. The most affected sites with EPTB were: Lymph nodes (66.5%), pleural cavity (15.6%), abdominal organs (11.1%), neuromeningeal (2.2%), joints (2.2%) and heart (2.2%). Overall, 84.4% of the study participants had a therapeutic success with males responding better 57.9% (p = 0.442). Therapeutic success was better (71.7%) in HIV negative EPTB patients (p = 0.787).

CONCLUSION

The prevalence of bacteriologically confirmed EPTB patients treated under program conditions in the littoral region of Cameroon is high with a therapeutic success of 84.4% and the lymph nodes is the most affected site.

Performance of an in-house real-time polymerase chain reaction for identification of Mycobacterium tuberculosis isolates in laboratory routine diagnosis from a high burden setting

Brazil is one of the high burden countries for tuberculosis, and a rapid diagnosis is essential for effective control of the disease. In the present study, an in-house real-time polymerase chain reaction (PCR) assay targeting the mpt64 gene for identification of Mycobacterium tuberculosis complex isolates was evaluated under routine diagnosis conditions in a reference laboratory. From May 2011 to July 2012, 1,520 isolates of mycobacteria were prospectively submitted for phenotypic and/or PRA-hsp65 identification and to real-time PCR. The mpt64 real-time PCR showed 99.7% sensitivity and 96% specificity and detected 79.4% of the cases missed by phenotypic and PRA-hsp65 identification. The in-house real-time PCR assay showed high sensitivity and specificity and was successfully implemented in the routine diagnosis of tuberculosis in a reference laboratory from a high burden setting.

Diagnosis and treatment of extrapulmonary tuberculosis

Extrapulmonary tuberculosis (EPTB) constitutes about 20% of all cases of tuberculosis (TB) in Korea. Diagnosing EPTB remains challenging because clinical samples obtained from relatively inaccessible sites may be paucibacillary, thus decreasing the sensitivity of diagnostic tests. Whenever practical, every effort should be made to obtain appropriate specimens for both mycobacteriologic and histopathologic examinations. The measurement of biochemical markers in TB-affected serosal fluids (adenosine deaminase or gamma interferon) and molecular biology techniques such as polymerase chain reaction may be useful adjuncts in the diagnosis of EPTB. Although the disease usually responds to standard anti-TB drug therapy, the ideal regimen and duration of treatment have not yet been established. A paradoxical response frequently occurs during anti-TB therapy. It should be distinguished from other causes of clinical deterioration. Surgery is required mainly to obtain valid diagnostic specimens and to manage complications. Because smear microscopy or culture is not available to monitor patients with EPTB, clinical monitoring is the usual way to assess the response to treatment.

Tuberculous pleural effusion

Tuberculous pleural effusion (TBPE) is the most common form of extrapulmonary tuberculosis (TB) in Spain, and is one of the most frequent causes of pleural effusion. Although the incidence has steadily declined (4.8 cases/100,000population in 2009), the percentage of TBPE remains steady with respect to the total number of TB cases (14.3%-19.3%). Almost two thirds are men, more than 60% are aged between 15-44years, and it is more common in patients with human immunodeficiency virus. The pathogenesis is usually a delayed hypersensitivity reaction. Symptoms vary depending on the population (more acute in young people and more prolonged in the elderly). The effusion is almost invariably a unilateral exudate (according to Light's criteria), more often on the right side, and the tuberculin test is negative in one third of cases. There are limitations in making a definitive diagnosis, so various pleural fluid biomarkers have been used for this. The combination of adenosine deaminase and lymphocyte percentage may be useful in this respect. Treatment is the same as for any TB. The addition of corticosteroids is not advisable, and chest drainage could help to improve symptoms more rapidly in large effusions.

Clinical evaluation of mtp40 polymerase chain reaction for the diagnosis of extra pulmonary tuberculosis

Rapid and sensitive detection of Mycobacterium tuberculosis from patient samples is vital for clinical diagnosis and treatment. The emergence of M. tuberculosis strains with either no copies or only a single copy of IS6110 in Asian countries makes the standard PCR based diagnosis of M. tuberculosis using IS6110 not reliable. We studied the diagnostic efficacy of the in-house PCR amplification of the candidate gene mtp40 as an alternative to IS6110 element based diagnosis. Clinical samples included pulmonary and extra-pulmonary specimens from TB suspected patients residing in Puducherry, South India and were analyzed using in-house PCR procedures targeting IS6110 element and mtp40 genes. Out of 317 clinical specimens analyzed, 132 (41.6 %) and 114 (36 %) were found positive for mtp40 PCR and IS6110 PCR, respectively. However, 18 specimens that were found to negative for IS6110 PCR were found positive for mtp40 PCR, which was further confirmed by DNA sequencing method. PCR amplification of mtp40 gene for the diagnosis of M. tuberculosis in clinical samples is fast, sensitive, and further identified clinical strains that lack IS6110 element in this region. It is clearly demonstrated that there is a significant difference between the two PCR procedures and the sensitivity and specificity levels of mtp40 PCR were found to be higher when compared with DNA sequencing method. Thus, mtp40 based PCR technique will be beneficial in diagnosis of TB where M. tuberculosis strains lack of IS6110 element is predominant.

Usefulness of multiplex PCR in the diagnosis of genital tuberculosis in females with infertility

The purpose of this investigation was to evaluate the usefulness of multiplex polymerase chain reaction (m-PCR) in detecting uterine tuberculosis in women with infertility. In a prospective study, endometrial curetting from 620 females with infertility were investigated using laparoscopy, hysteroscopy, histopathology, smear microscopy, mycobacterial culture in BACTEC MGIT™ 960, and in-house m-PCR. The mean age of the women was 29.75 ± 4.66 years. The majority (596) sought medical attention for infertility; of them, 455 (76.34 %) presented with primary and 141 (23.65 %) with secondary infertility. A total of 158 (25.48 %) women were diagnosed as having uterine tuberculosis by at least one of the diagnostic methods. Among them, laparoscopy was positive in 46 (29.11 %), hysteroscopy in 77 (48.73 %), histopathology in only 8 (5.06 %), smear for acid fast bacilli in 4 (2.53 %), and liquid culture in 24 (15.18 %) patients. The in-house m-PCR was positive in 135 (85.44 %) women. Of these, 129 (95.55 %) samples were positive for Mycobacterium tuberculosis, while 6 (4.44 %) were positive for non-tuberculous mycobacterial DNA. Of the 129 M. tuberculosis PCR-positive women, 112 received anti-tubercular treatment and 23 of these conceived and fell pregnant after the completion of treatment. For the diagnosis of uterine tuberculosis, m-PCR was found to be the most efficient diagnostic tool compared to the other methods.

Feasibility of the Interferon-γ Release Assay for the Diagnosis of Genitourinary Tuberculosis in an Endemic Area

Purpose

To evaluate the feasibility of the interferon-gamma release assay (IGRA) as a supplementary diagnostic tool for the diagnosis of genitourinary tuberculosis (GUTB).

Materials and Methods

Fifty-seven patients who were tested with the IGRA to diagnose GUTB were included. All patients had clinical or radiologic features suspicious for GUTB. Signs and symptoms included chronic dysuria with long-standing sterile pyuria, renal calcification with distorted renal calyces and contracted renal pelvis, and chronic epididymitis. Patients who had a history of tuberculosis in other organs were excluded. Tests including IGRA, urine acid-fast bacilli (AFB) stain and culture, urine tuberculosis polymerase chain reaction (UT-PCR), and radiological examinations were performed to confirm GUTB. The medical records of the patients were reviewed retrospectively.

Results

The IGRA result was positive in 30 patients (52.6%). The results of the urine AFB stain and culture were positive in 5 patients (8.8%) and 7 patients (12.2%), respectively. The results of UT-PCR were positive in 9 patients (15.8%). The 7 patients who showed positive results in the urine AFB stain and culture also had positive results on the IGRA. A UT-PCR-negative patient was diagnosed with GUTB by positive results on both the IGRA and AFB stain and culture.

Conclusions

The IGRA might feasibly be used as a supplementary or screening tool for the diagnosis of GUTB in addition to urine AFB stain and culture. Further studies for statistical evaluation of its sensitivity, specificity, and efficacy are needed.

Diagnostic value of PCR in genitourinary tuberculosis

Genitourinary tuberculosis is a disease of the genitourinary system which includes the entire urinary tract and reproductive system. Genital tuberculosis is an important cause of female infertility, especially in developing nations like India. In the present study, a total of 257 clinical specimens comprising of endometrial biopsy (109), endometrial curetting (42), menstrual blood (8), semen (17), placenta (11) and urine (70) were collected from patients and subjected for PCR, Culture and AFB detection. The endometrial biopsy, endometrial curetting, menstrual blood, semen, placenta, urine showed 30.2, 45.2,12.5, 5.8, 27.2, 31.4 %, positivity rate for tuberculosis by PCR, 7.3, 9.5, 25.0, 0, 9, 8.5 % by culture and 1.8, 2.3, 0, 0, 0, 2.8 % respectively by AFB smear. Being a novel, rapid technique, PCR is the method of choice for rapid diagnosis and management of genitourinary tuberculosis shared with the other concerned tests. This study reveals that genital tuberculosis can occur in any age group, however, the majority of patients were from reproductive age (nearly 75 % of them were from 20-45 years of age) group.

Rapid Diagnosis of Genital Tuberculosis by Real-time Polymerase Chain Reaction

Objective

Rapid diagnosis of genital tuberculosis (GTB) is essential as it is an important cause of infertility among women. Diagnosis can be done by imaging techniques, direct visualization by endoscopy, serology, histopathology, culture and polymerase chain reaction (PCR) tests. Laparoscopy detects macroscopic changes only; histology is only suggestive and not confirmatory unless acid fast bacilli (AFB) are demonstrated in the lesion but sensitivity is poor in paucibacillary disease. Culture methods are the gold standard but slow growth of most pathogenic mycobacteria delays the diagnosis. PCR can rapidly detect even few copies of DNA with high sensitivity and specificity.

Aim

Comparative evaluation of AFB smear examination, culture in Middlebrook 7H9 media and IS6110 based real-time PCR assay for the detection of mycobacteria in various female genital samples.

Materials and methods

A total of 555 female genital samples like endometrial and fallopian tube biopsies, menstrual blood and vaginal discharge were processed by modified Petroff's method. The deposit was used for detection of mycobacteria by AFB smear, culture on Middlebrook 7H9 media and IS6110 based real-time PCR.

Results

Out of 555 samples, 25.22 % (140/555) were positive by the combination of all the methods used. Overall positivity by real-time PCR alone was 23.78% (132/555), by culture 8.28% (46/555) and 2.70% (15/555) by AFB smear examination. Out of total positives, 94.28% (132/140) were positive by PCR alone, 32.85% (46/140) by culture and 10.71% (15/140) by AFB smear. Eight (5.71%) culture positive samples were negative by smear and PCR, six of these were nontubercular mycobacteria (NTM) and two samples had PCR inhibitors as confirmed by spiking with positive DNA. Contamination was observed in 25/555 (4.5%) which were reported negative by culture but three of these were PCR positive. AFB smear results were available in 1 hour, PCR in 1 day and culture in 4 to 6 weeks.

Conclusion

PCR was found to be the most rapid and sensitive (94.28%) method, 9-fold more sensitive than smear examination and 3-fold than the culture for detection of mycobacteria. Results were available in 4 to 6 weeks time for culture but in only 1 day by PCR. IS6110 PCR can detect only MTB and not the NTM. Use of multiplex PCR with genus and MTB specific primers will increase the sensitivity of test but care needs to be taken to prevent false positivity due to cross contamination and false negative due to PCR inhibitors.

How to cite this article

Malhotra B, Sinha P, Hooja S, Vyas L. Rapid Diagnosis of Genital Tuberculosis by Real-time Polymerase Chain Reaction. J South Asian Feder Obst Gynae 2012;4(1):39-42.

Targeted detection of 65 kDa heat shock protein gene in endometrial biopsies for reliable diagnosis of genital tuberculosis

OBJECTIVE

To evaluate the clinical utility of PCR compared with other available diagnostic modalities in prompt diagnosis of female genital tuberculosis causing infertility.

STUDY DESIGN

Prospective case-controlled trial. Premenstrual endometrial biopsy specimens were collected from 150 infertile women of reproductive age group suspected of having genital tuberculosis. All patients underwent diagnostic endoscopy (laparoscopy and hysteroscopy) and the samples obtained were subjected to microscopy, culture by the BACTEC 460 TB System, histopathology and polymerase chain reaction (PCR) for detection of 165 bp region of 65 kDa gene of Mycobacterium tuberculosis. The results were correlated with the laparoscopic findings.

RESULTS

While the laparoscopy/hysteroscopy findings were indicative of tuberculosis in 12.6% of cases, 14.6% of the specimens showed evidence of 65 kDa gene of M. tuberculosis and only 3.33%, 1.33% and 0.66% were positive by culture, smear and histopathology, respectively.

CONCLUSION

Since laparoscopy, hysteroscopy other endoscopic procedures are associated with operative risks and may cause flaring of infection, and other conventional laboratory tests including histopathology have poor sensitivity, PCR-based detection of 65 kDa gene of M. tuberculosis in endometrial biopsy specimens could be a promising molecular diagnostic technique compared to conventional methods of diagnosis.

Proinflammatory Cytokine Profile in Active Kidney Tuberculosis Patients

INTRODUCTION

Mycobacterium tuberculosis is a facultative intracellular pathogen that developes specific T cell response expressed by the production of IL-12, IFN-gamma, and TNF-alpha. The response has been quite well investigated in the experimental models, however, there is little information about certain cytokine levels in patients with extrapulmonary tuberculosis. The shortage of data pertains also to its most common form-kidney tuberculosis, especially when bacilli dissemination into the blood circulation has occurred.

OBJECTIVES

The aim of our study was to examine simultaneously the frequency of Mycobacterium tuberculosis presence in the blood circulation and the serum cytokine concentration during kidney tuberculosis to approach their relationship in the clinical infection process. It is considered that cytokine levels do not correlate with localisation of tuberculosis (pulmonary vs. extrapulmonary), however, there is little information about the cytokine levels in patients with kidney tuberculosis.

MATERIALS AND METHODS

30 patients attending the urology clinic with suspicion of kidney tuberculosis were evaluated. Serum concentrations of selected cytokines in patients with urine, urine and blood Mycobacterium tuberculosis presence were quantified by ELISA and compared to PCR negative patient and group of healthy people.

RESULTS

Our study demonstrates the increase of TNF-alpha and IL-12 level in comparison to control group. TNF-alpha concentration was about 2-fold higher in the positive patients than it was in control group; IL-12 concentration was about 4-fold higher and the differences between IL-12 levels were statistically important (p < 0.05). However, no significant differences were found in IFN-gamma level among all groups. Using Spearman correlation rank test, a significant correlation was found between TNF-alpha and IL-12 in the positive patient group. The correlation factor was more significant for the group of patients with Mycobacterium tuberculosis present in blood and urine than it was in urine positive PCR group (r = -0.66 vs. r = -0.51).

Diagnosis and treatment of tuberculous pleural effusion in 2006

Tuberculous (TB) pleural effusion occurs in approximately 5% of patients with Mycobacterium tuberculosis infection. The HIV pandemic has been associated with a doubling of the incidence of extrapulmonary TB, which has resulted in increased recognition of TB pleural effusions even in developed nations. Recent studies have provided insights into the immunopathogenesis of pleural TB, including memory T-cell homing and chemokine activation. The definitive diagnosis of TB pleural effusions depends on the demonstration of acid-fast bacilli in the sputum, pleural fluid, or pleural biopsy specimens. The diagnosis can be established in a majority of patients from the clinical features, pleural fluid examination, including cytology, biochemistry, and bacteriology, and pleural biopsy. Measurement of adenosine deaminase and interferon-gamma in the pleural fluid and polymerase chain reaction for M tuberculosis has gained wide acceptance in the diagnosis of TB pleural effusions. Although promising, these tests require further evaluation before their routine use can be recommended. The treatment of TB pleural effusions in patients with HIV/AIDS is essentially similar to that in HIV-negative patients. At present, evidence regarding the use of corticosteroids in the treatment of TB pleural effusion is not clear-cut.

Enzyme-linked immunosorbent assay of nucleic acid sequence-based amplification for molecular detection of M. tuberculosis

An enzyme-linked immunosorbent assay of nucleic acid sequence-based amplification (NASBA-ELISA) was developed for molecular detection of Mycobacterium tuberculosis. The primers targeting 16S rRNA were used for the amplification of bacterial RNA by the isothermal digoxigenin (DIG)-labeling NASBA process, resulting in the accumulation of DIG-labeled RNA amplicons. The amplicons were hybridized with a specific biotinylated DNA probe which was non-covalently immobilized on streptavidin-coated microtiter plate. The RNA-DNA hybrids were colorimetrically detected by the addition of an anti-DIG antibody HRP conjugate and 2,2-azino-di-(3-ethylbenzthiazolinsulfonate) substrate. Using this method, as little as 1 x 10(2) CFU ml(-1) of M. tuberculosis was detected within less than 5h. Results obtained from the clinical specimens showed 85.7% and 96% sensitivity and specificity, respectively. No interference was encountered in the amplification and detection of M. tuberculosis in the presence of non-target bacteria, confirming the specificity of the method.

Differentiation of Mycobacterial species by hsp65 duplex PCR followed by duplex-PCR-based restriction analysis and direct sequencing

Here we describe a novel duplex PCR method which can differentiate Mycobacterium tuberculosis and nontuberculosis mycobacteria (NTM) strains by amplifying hsp65 DNAs of different sizes (195 and 515 bp, respectively). The devised technique was applied to 54 reference and 170 clinical isolates and differentiated all strains into their respective groups with 100% sensitivity and specificity. Furthermore, a duplex PCR-restriction analysis (duplex PRA) and a direct sequencing protocol were developed to differentiate NTM strains at the species and subspecies levels based on previously reported hsp65 DNA sequences (H. Kim et al., Int. J. Syst. Evol. Microbiol. 55:1649-1656, 2005) and then applied to 105 NTM clinical isolates. All NTM isolates were clearly differentiated at the species and subspecies levels by subsequent procedures (PRA or direct sequencing) targeting 515-bp NTM duplex PCR amplicons. Our results suggest that novel duplex PCR-based methods are sensitive and specific for identifying mycobacterial culture isolates at the species level.

Improved diagnostic value of PCR in the diagnosis of female genital tuberculosis leading to infertility

Histopathological and mycobacteriological examinations have limited utility in the diagnosis of genital tuberculosis. In this double-blind study, 61 samples, consisting of endometrial aspirates (EAs), endometrial biopsies (EBs) and fluid from the pouch of Douglas (POD), from 25 women suffering from infertility were investigated for the presence of the mpt64 gene of Mycobacterium tuberculosis by PCR and correlated with laparoscopic findings. PCR demonstrated M. tuberculosis DNA in 14 out of 25 patients (56.0 %), compared to one smear with acid-fast bacilli (1.6 %) and two culture-positive samples (3.2 %). The presence of M. tuberculosis DNA was observed in 53.3 % of EBs, 47.6 % of EAs and 16.0 % of POD fluid samples. All patients with laparoscopy suggestive of tuberculosis, 60 % of those with a probable diagnosis and 33 % of those with incidental findings were positive by PCR. However, one EA sample from an infertile patient with normal laparoscopy was also positive. Multiple sampling from different sites and amplification of the mpt64 gene segment by PCR offered increased sensitivity in determining tuberculous aetiology in female infertility.

In-house nucleic acid amplification tests for the detection of Mycobacterium tuberculosis in sputum specimens: meta-analysis and meta-regression

BACKGROUND

More than 200 studies related to nucleic acid amplification (NAA) tests to detect Mycobacterium tuberculosis directly from clinical specimens have appeared in the world literature since this technology was first introduced. NAA tests come as either commercial kits or as tests designed by the reporting investigators themselves (in-house tests). In-house tests vary widely in their accuracy, and factors that contribute to heterogeneity in test accuracy are not well characterized. Here, we used meta-analytical methods, including meta-regression, to identify factors related to study design and assay protocols that affect test accuracy in order to identify those factors associated with high estimates of accuracy.

RESULTS

By searching multiple databases and sources, we identified 2520 potentially relevant citations, and analyzed 84 separate studies from 65 publications that dealt with in-house NAA tests to detect M. tuberculosis in sputum samples. Sources of heterogeneity in test accuracy estimates were determined by subgroup and meta-regression analyses. Among 84 studies analyzed, the sensitivity and specificity estimates varied widely; sensitivity varied from 9.4% to 100%, and specificity estimates ranged from 5.6% to 100%. In the meta-regression analysis, the use of IS6110 as a target, and the use of nested PCR methods appeared to be significantly associated with higher diagnostic accuracy.

CONCLUSION

Estimates of accuracy of in-house NAA tests for tuberculosis are highly heterogeneous. The use of IS6110 as an amplification target, and the use of nested PCR methods appeared to be associated with higher diagnostic accuracy. However, the substantial heterogeneity in both sensitivity and specificity of the in-house NAA tests rendered clinically useful estimates of test accuracy difficult. Future development of NAA-based tests to detect M. tuberculosis from sputum specimens should take into consideration these findings in improving accuracy of in-house NAA tests.

Molecular analyses of mycobacteria other than the M. tuberculosis complex isolated from Northern Ireland cattle

Mycobacteria other than the Mycobacterium tuberculosis complex (MOTT), isolated from Northern Ireland cattle, were identified by PCR amplification of the 16S rRNA gene, and subsequent reverse cross blot hybridisation and sequence analyses. Elucidation of the MOTT species was to facilitate specificity testing of new and existing diagnostic test reagents for bovine tuberculosis. The presence of the genes for potential diagnostic antigens: MPB70, MPB64, ESAT-6 and CFP-10 in the isolated MOTT species was investigated. Molecular analyses of cultured isolates from bovine lymph node specimens of 48 cattle identified a wide variety of mycobacterial species including Mycobacterium nonchromogenicum, Mycobacterium malmoense, Mycobacterium bohemicum, Mycobacterium paratuberculosis, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium holsaticum, Mycobacterium palustre, Mycobacterium sp. IWGMT 90210, Mycobacterium sp. LIV-2129, a potentially novel mycobacterial species (EMBL/GenBank/DDBJ Accession Number AJ617495) and Rhodococcus equi. Apart from M. kansasii, the results of traditional (standard phenotypic and biochemical) and molecular identification methods did not correlate well, with traditional methods identifying fewer species. Most of the species identified were either recognised pathogenic or potential pathogenic species. The genes for ESAT-6, CFP-10 and, unusually, MPB64 were detected in M. kansasii only. The MPB70 gene was not detected in any of the species. This study supported restricted species distribution of these genes as well as identifying a different range of MOTT species that could be included in specificity testing of new diagnostic reagents for bovine tuberculosis.

Diagnosis of tuberculosis: available technologies, limitations, and possibilities

Rapid diagnosis and treatment are important for preventing transmission of Mycobacterium tuberculosis. However, the diagnosis of tuberculosis continues to pose serious problems, mainly because of difficulties in differentiating between patients with active tuberculosis and those with healed lesions, normal mycobacterium boris BCG (Bacillus Calmette Guerin) vaccinated individuals, and unvaccinated Manteux positives. Physicians still rely on conventional methods such as Ziehl-Neelsen (ZN) staining, fluorochrome staining, sputum culture, gastric lavage, and other non-traditional methods. Although the tuberculin test has aided in the diagnosis of tuberculosis for more than 85 years, its interpretation is difficult because sensitization with nontuberculous mycobacteria leads to false-positive tests. There have been numerous unsuccessful attempts to develop clinically useful serodiagnostic kits for tuberculosis. A number of proteinaceous and nonprotein antigens (such as acyltrehaloses and phenolglycolipids) have been explored from time to time for the development of such assays but they have not proved to be clinically useful. It has been difficult to develop an ELISA utilizing a suitable antigen because M. tuberculosis shares a large number of antigenic proteins with other microorganisms that may or may not be pathogenic. With the advent of molecular biology techniques, there have been significant advances in nucleic acid-based amplification and hybridization, which are helping to rectify existing flaws in the diagnosis of tuberculosis. The detection of mycobacterial DNA in clinical samples by polymerase chain reaction (PCR) is a promising approach for the rapid diagnosis of tuberculous infection. However, the PCR results must be corrected for the presence of inhibitors as well as for DNA contamination. In the modern era of genetics, marked by proteomics and genomics, the day is not far off when DNA chip-based hybridization assays will instantly reveal mycobacterial infections.

Mtp-40 and alpha antigen gene fragment amplification for the detection of Mycobacterium tuberculosis in Colombian clinical specimens

In this study, the use of Mtp-40 and alpha antigen polymerase chain reaction (PCR) amplification fragments for the precise tuberculosis (TB) diagnosis was evaluated. One hundred and ninety two different samples were obtained from 113 patients with suspected TB. Mtp-40 and alpha antigen protein genes were amplified by the PCR technique and compared to both the "gold standard" (culture) test, as well as the clinical parameters (including a clinical record and X-ray film exam in 113 patients). Thirty-eight of the 113 patients had a presumptive clinical diagnosis of TB; 74% being detected by PCR technique, 58% by culture and 44% by direct microscopic visualization. Weconclude that it is possible to use PCR as a suitable technique for the detection of any mycobacteria by means of the alpha antigen product, or the specific infection of Mycobacterium tuberculosis by means of the mtp-40 gene. This might be a good supporting tool in difficult clinical TB diagnosis and pauci-bacillary cases.

Clinical evaluation of Amplicor Mycobacterium detection system for the diagnosis of pulmonary mycobacterial infection using sputum

SETTING

The Amplicor Mycobacterium detection kit was evaluated for the diagnosis of active pulmonary mycobacterial infection using sputum.

OBJECTIVE

To assess the clinical usefulness of the Amplicor Mycobacterium kit for the diagnosis of pulmonary tuberculosis and non-tuberculous mycobacterial infection in the country of medium prevalence.

DESIGN

All the patients were diagnosed with bacterial, histopathological, and clinical 'gold standard'. The sensitivity and specificity for diagnosing clinically active pulmonary tuberculosis and Mycobacterium avium and Mycobacterium intracellulare infections were evaluated comparing Amplicor results and clinical diagnosis.

RESULTS

A total of 1088 sputum specimens were collected from 780 in and out patients. Mycobacteria were recovered from 339 specimens by culture. The sensitivity and specificity of conventional culture method for the diagnosis of pulmonary tuberculosis were 60.2% and 99.8% respectively based on the number of patients. The figures for Amplicor were 61.8% and 97.4% respectively. There was no statistical significant difference between these methods. In rapidity, the Amplicor was significantly superior to the microscopy method in sensitivity.

CONCLUSION

Patients with Amplicor positive and conventional negative result had mostly mycobacteria related diseases. The Amplicor positive result indicated mostly active mycobacterial infection and was clinically useful for rapid diagnosis.

Specificities and functions of the recA and pps1 intein genes of Mycobacterium tuberculosis and application for diagnosis of tuberculosis

The worldwide recrudescence of tuberculosis and the widespread appearance of antibiotic resistance have strengthened the need for rapid and specific diagnostic tools. The prevailing microbiological identification of Mycobacterium tuberculosis, the causative agent of tuberculosis, which implies the use of in vitro cultures and acid-fast staining microscopy, is time-consuming. Detection of M. tuberculosis directly in clinical samples through PCR amplification of mycobacterium-specific genes, designed to shorten diagnostic delay, demonstrated reliability and high sensitivity. However, the quality of the diagnosis depends on the specificity of the target sequence for M. tuberculosis complex strains. In the present study, we demonstrated the specificity of recA and pps1 inteins for this complex and thus the feasibility of using intein-coding sequences as a new target for PCR diagnosis. Indeed, the recA and pps1 genes of 36 clinical isolates of M. tuberculosis and 10 field strains of M. bovis were found to be interrupted by an intein sequence at the RecA-a and Pps1-b sites, respectively, while a large number of nontuberculous mycobacterial species failed to demonstrate these insertions. Besides, the MtuPps1, which was cloned and expressed in Escherichia coli, was shown to possess an endonuclease activity. The intein cleaves the 40-bp sequence spanning the intein insertion site Pps1-b in the inteinless pps1 gene. In addition to the PCR amplification of recA and pps1 intein genes as a tool for diagnosis, the specific endonuclease activity could represent a new molecular approach to identify M. tuberculosis.

Potential use of Amplicor PCR kit in diagnosing pulmonary tuberculosis from gastric aspirate

Polymerase chain reaction (PCR) detection of mycobacteria from gastric aspirate for the diagnosis of tuberculosis is not fully evaluated up to now. A total of 116 gastric aspirate specimens were collected from patients with suspected pulmonary tuberculosis. The breakdown of diagnosis was 67 pulmonary tuberculosis, 16 nontuberculous mycobacterial infection, 5 extra pulmonary tuberculosis, and 28 other lung diseases. The conventional methods were shown to have a sensitivity of 47.8% and a specificity of 79.6%; on the other hand, Amplicor had 34.9% and 97.0%, respectively. The Amplicor provided a more rapid and specific method for diagnosing tuberculosis and was more useful than the conventional.

Detection and diagnosis of mycobacterial pathogens using PCR

In the year 2001, it is estimated that 3 million people will die from tuberculosis, caused by the infectious agent, Mycobacterium tuberculosis. After decades of decline in the disease, the resurgence of tuberculosis seen worldwide in the 1990s sparked a renewed interest and commitment of funds for research into M. tuberculosis and other pathogenic mycobacterial species. The discovery of the PCR in the 1980s has had a major influence on the progress made possible in the study of these fastidious, tough-walled and slow-growing mycobacterial species. In the last 10 years, PCR has allowed us to amplify parts of the genome, decipher the nucleotide sequence, discover new mycobacterial species, determine epidemiological relationships between strains and identify genetic changes involved in drug resistance.

Polymerase chain reaction in clinically suspected genitourinary tuberculosis: comparison with intravenous urography, bladder biopsy, and urine acid fast bacilli culture

OBJECTIVES

To evaluate the role of urinary polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis (MTb) in patients with a clinical suspicion of genitourinary tuberculosis (GUTB) and to compare its sensitivity with intravenous urography (IVU), bladder biopsy, and urine culture for acid fast bacilli (AFB).

METHODS

The study was carried out between September 1997 and December 1998 in 42 patients with a clinical suspicion of GUTB. Their clinical features, organ involvement, and investigation results were studied. The diagnostic yield of urinary PCR for MTb and its sensitivity in comparison with routine urine AFB culture, bladder biopsy, and IVU were assessed.

RESULTS

There were 25 male and 17 female patients, with a mean age of 31.04 years. Patients suspected of having GUTB most often presented with irritative voiding symptoms. Two patients had abnormal renal parameters. Of the 42 patients clinically suspected of having GUTB, radiologic abnormalities suggestive of GUTB were found in 37 (88.09%); MTb was isolated in the urine AFB culture in 13 (30.95%); bladder biopsy was positive in 11 (45.83%); and urinary PCR for MTb was positive in 34 cases (80.95%). Of 35 cases of proven GUTB, IVU was suggestive of the diagnosis in 32 (91.42%) and MTb was isolated in the urine AFB culture in 13 cases (37.14%). Bladder biopsy was positive in 11 (45. 83%) of 24 patients in whom biopsy was taken, and urinary PCR for MTb was positive in 33 (94.29%).

CONCLUSIONS

A high index of suspicion is necessary for a diagnosis of GUTB. In clinically suspected cases, IVU may be suggestive of GUTB, but it is not specific. In the present study, IVU was suggestive in 88.09% of patients. MTb was isolated in the urine AFB culture in only 37.14% of patients, and bladder biopsy was positive in 45.83%. Urinary PCR for MTb was the most sensitive indicator and was positive in 94.29% of patients. It is evident from this series that PCR provides a much faster diagnosis of urinary MTb. It is a rapid, sensitive, and specific diagnostic method and avoids a delay in starting treatment.

Polymerase chain reaction in the diagnosis of tuberculosis

A rapid, sensitive, specific and yet economical method for the diagnosis ofM. tuberculosis and other mycobacteria in clinical specimen is a desperate and urgent requirement of the day in the laboratory diagnosis and hence management of tuberculosis. This need is further accentuated by emerging diseases like multi drug resistant tuberculosis, tuberculosis in AIDS patients and opportunistic mycobacterial infections, which do not respond to conventional anti TB therapy. Molecular methods, particularly PCR based detection ofM. tuberculosis, has come a long way since it was first described about fifteen years ago. Several probes have been developed and some of them, particularly the IS6110 and TB400 have been validated on several clinical samples. The latter has been validated on a variety of clinical specimens along with a simple sample processing method. Polymerase chain reaction based diagnosis ofM. tuberculosis has been introduced as one of the routine/confirmatory tests in clinical microbiology laboratory in some countries like Canada, the United States and the United Kingdom several years ago. The possibility of introducing PCR based direct diagnosis of drug resistance is being explored in some laboratories, particularly for drugs like rifampicin. The evolution and application of PCR for diagnosis ofM. tuberculosis is being analysed and discussed in this review.

A PCR-colorimetric microwell plate hybridization assay for detection of Mycobacterium tuberculosis and M. avium from culture samples and Ziehl-Neelsen-positive smears

Differentiation between Mycobacterium tuberculosis and M. avium is essential for the treatment of mycobacterial infections. We have developed an easy and rapid detection assay for the diagnosis of mycobacterial diseases. This is a PCR-hybridization assay based on selective amplification of a 16S rRNA gene sequence using pan-Mycobacterium primers followed by hybridization of the amplification products to biotinylated M. tuberculosis and M. avium-specific probes. A total of 55 mycobacterial isolates were tested. For all isolates, results concordant with those of conventional identification methods were obtained. Moreover, we developed a method for extraction of DNA from Ziehl-Neelsen-positive smears which allows the recovery of intact target DNA in our PCR-hybridization assay. Our method was able to confirm all culture results for 59 Ziehl-Neelsen-positive smears from clinical specimens (35 sputum, 11 lymph node biopsy, 6 stool, 4 pus, 2 urine, and 1 pericardial fluid specimens). These data suggest that our PCR-hybridization assay, which is simple to perform and less expensive than commercial probe methods, may be suitable for the identification of M. tuberculosis and M. avium. It could become a valuable alternative approach for the diagnosis of mycobacterial infections when applied directly to DNA extracted from Ziehl-Neelsen-positive smears as well.

Heteroduplex mobility assay for rapid, sensitive and specific detection of mycobacteria

We report an improved method for the detection and identification of mycobacteria using PCR and the heteroduplex mobility shift assay (HMA). The HMA for detection of mycobacteria was based on the microheterogeneity within the DNA coding sequences for 16S rRNA. A remarkable shift between single-stranded, heteroduplex and homoduplex bands in PAGE was observed among the Mycobacterium spp. tested. The Mycobacteria HMA (MHMA) of amplified PCR products from mycobacteria DNA coding for 16S rDNA derived from culture showed a specific heteroduplexes formed among different Mycobacterium species. Other bacterium species were distinguished from Mycobaterium due to slow migrating heteroduplexes mobility bands observed when M. bovis (BCG), M. avium, or M. fortuitum were used as a standard. The specific heteroduplexes were detected when as little as 1 etag of DNA template was used, although better results were obtained with 5 etag and when PCR products of sample test and mycobacterium standard were mixed at a ratio of 1.8. To correctly evaluate the feasibility of using MHMA to detect and identify mycobacteria, 15 clinical sample patients were tested. All MTB-positive clinical samples were identified by MHMA as well as the negative samples. In addition, MHMA will, in principle, be applicable to the detection and classification of any microorganism showing differences within the 16S rRNA as well as to the identification of new and unrecognized bacterial species.

PCR based detection of mycobacteria in paraffin wax embedded material routinely processed for morphological examination

BACKGROUND

The incidence of mycobacterial infections has increased during the past five years. A prompt diagnosis is indispensable for initiating appropriate treatment. Because culturing of mycobacteria takes three to six weeks and sensitivity of microscopic detection of acid fast bacilli is low, amplification methods provide promising possibilities. Recently, the polymerase chain reaction (PCR) has been shown to be useful for confirming a mycobacterial infection, especially in cases with unexpected histological findings or lack of suitable material for culturing.

AIMS

To evaluate the impact of PCR based techniques in the detection of mycobacterial infections in uncultured routine histological specimens as an alternative to surgical pathology.

METHODS

Two hundred and twenty nine formalin fixed and paraffin wax embedded samples from 141 patients with clinical or histological suspicion of a mycobacterial infection were investigated using three different PCR assays and Southern blotting. PCR results were compared with histology and culture and the patients' clinical findings.

RESULTS

When using culture as the reference method, the sensitivity for the detection of mycobacteria of the tuberculosis complex was 90%, specificity was 92%, the positive predictive value was 81%, and the negative predictive value was 96%. The sensitivity for the detection of nontuberculous mycobacteria was 100% and specificity was 78%, the positive predictive value was 26%, and the negative predictive value was 100%. The patients' clinical findings supported the PCR positive results, indicating a mycobacterial infection in 11 of 18 initially culture negative cases and in 21 of 35 PCR positive cases without culture results.

CONCLUSIONS

These results indicate that PCR based techniques are sensitive, specific, and rapid methods for the detection of mycobacteria in routinely processed paraffin wax embedded and formalin fixed histological samples.

Detection ofAspergillus Fumigatus based on Asp fl gene in clinical specimens

Oligonucleotide primers were synthesised based on the gene sequence of an 18 kDa allergen/antigen ofA. fumigatus isolated from a pathogenic strain. Polymerase chain reaction (PCR) was carried out using the forward and reverse primers and genomic DNA ofA. fumigatus, A. flavus andA. niger as template. This resulted in a PCR product of 480 bp with onlyA. fumigatus. The absence of PCR product inA. flavus andA. niger with the primers of Asp fl facilitated use of these primers for detection ofA. fumigatus in clinical specimens of patients. The results were compared with microscopy, culture and serology. Application of PCR test to clinical samples of aspergillosis patients is discussed.

Detection of IgG and IgA against the mycobacterial antigen A60 in patients with extrapulmonary tuberculosis

BACKGROUND

Diagnosis of extrapulmonary tuberculosis is often difficult to establish using standard methods. Serological techniques based on detection of antibodies against mycobacterial antigen A60 have shown good sensitivity and specificity in pulmonary tuberculosis. The present study was undertaken to define the diagnostic accuracy of testing for IgG and IgA against A60 in extrapulmonary tuberculosis.

METHODS

One hundred and ninety eight subjects were studied: 42 patients with extrapulmonary tuberculosis confirmed by microbiology and/or histology, 24 subjects with healed pulmonary or extrapulmonary tuberculosis, 44 patients with a defined non-tuberculous disease, and 88 healthy volunteers (44 PPD negative and 44 PPD positive). Detection of IgG and IgA against A60 antigen was carried out by enzyme-linked immunosorbent assay. Cut off values were determined by receiver operating characteristic curves.

RESULTS

Sensitivity of the IgG test was 73.8% in extrapulmonary tuberculosis, while the specificity was 96.1%. The IgA test showed a sensitivity of 69.0% with a specificity of 93.6%. Combination of the IgG and IgA tests showed a sensitivity of 80.9% and a specificity of 92.3%. Patients with extrapulmonary tuberculosis showed significantly higher titres of both IgG and IgA against A60 than other groups.

CONCLUSIONS

Anti-A60 IgG or IgA tests are characterised by good sensitivity and specificity. The combined use of both tests allows an increase in diagnostic accuracy of extrapulmonary tuberculosis.

Rapid diagnosis and strain differentiation of Mycobacterium bovis in radiometric culture by spoligotyping

An assessment of spoligotyping for rapid detection and strain typing of Mycobacterium bovis isolates in radiometric culture was made. Spoligotyping was applied to BACTEC 12B broth cultures of 54 lesioned bovine lymph node specimens from 44 herds in Northern Ireland. A nucleic acid sequence capture technique was performed on BACTEC cultures at growth index points of approximately (approximately) 60, approximately 200, and 999. Definitive spoligotype patterns were obtained for 90.4% and 94.2% of all 52 BACTEC culture-positives at growth indexes approximately 60 and approximately 200, respectively. Within 10 days, definitive spoligotype patterns were obtained for 84.6% of the culture-positives. This technique, therefore, allowed earlier and more accurate diagnosis of M. bovis than traditional methodologies, as well as simultaneous strain differentiation. Application of this molecular tool to BACTEC cultures would be a significant advance in bovine tuberculosis eradication programmes. Seven distinct spoligotype patterns were identified in this study, 2 of which (ST21 and ST25), had not been identified previously in cattle from Northern Ireland. Two spoligotype patterns (ST1 and ST2) accounted for 80.7% of the culture-positives. These were found to have widespread geographic distribution, whereas 1 spoligotype pattern (ST14) had limited geographical distribution.

Mycobacterial DNA not detected in liver sections from patients with primary biliary cirrhosis

BACKGROUND/AIMS

Recent studies in primary biliary cirrhosis have reported the detection of serum antibodies against Mycobacterium gordonae and of mycobacterial DNA in liver sections. The aim of this study was to investigate whether mycobacterial DNA is present in liver biopsy material in primary biliary cirrhosis.

METHODS

Archival liver biopsy specimens from 11 patients with primary biliary cirrhosis (10 female, mean age 52 years) and 11 patients with autoimmune hepatitis (10 female, mean age 53 years) were identified. Positive control tissue comprised five archival lymph node specimens from patients with tuberculous lymphadenopathy, three of which had stained positive on ZN staining, and also a liver biopsy specimen from a patient with tuberculous hepatitis (ZN positive). Fixed sections were deparaffinised and DNA was extracted by mechanical disruption with glass beads. DNA was purified by use of diatoms and lysis in guanidinium thiocyanate in a technique previously validated for archival DNA. Primers were directed to amplify a partial 16S ribosomal RNA gene yielding the species-specific character for mycobacteria, and also to amplify the constitutively-expressed human gene GAPDH.

RESULTS

The polymerase chain reaction was shown to be capable of detecting 1 fg of M. gordonae DNA in 'spiked' samples, equivalent to 1-5 bacterial cells. No mycobacterial DNA was detected in liver biopsy samples from either the primary biliary cirrhosis or autoimmune hepatitis groups. Of the tuberculous control sections, mycobacterial DNA was detected in four of five lymph nodes and the liver biopsy specimen. GAPDH amplification was detected in all tested samples from liver disease and tuberculous control samples.

CONCLUSION

These data do not support a role for mycobacteria in the aetiology of primary biliary cirrhosis.

Immuno-polymerase chain reaction for detection ofAspergillus fumigatus

A number of Aspergillus infections are caused by the opportunistic fungal pathogenAspergillus fumigatus in humans especially under immunosuppressed conditions. Major forms of the disease include invasive aspergillosis, allergic bronchopulmonary aspergillosis and aspergilloma. A procedure that uses chitinase and microwave treatment is described for the extraction of genomic DNA of Aspergillus species from the sputum and bronchial aspirate of patients with established aspergillosis. Detection ofA.fumigatus was compared by culture, microscopy, serology by ELISA, immunodiffusion, agarose gel electrophoresis of PCR products and colorimetric immuno-PCR. A colorimetric method for the detection of PCR product was developed based on immunoaffinity reactions. Out of the clinical samples tested from nineteen patients, fourteen were positive and five were negative by all the methods tested. It was established that at least 1 pg of DNA was extractable from the clinical samples sufficient to produce enough quantities of PCR product for detection on agarose gel or by immunoaffinity based color reaction. An absorbance value of 0.9 to 1.5 against 0.2 for negative control was obtained at 405 nm for colorimetric immuno-PCR. This method can be exploited for screening large number of clinical samples from immunocompromized as well as from suspected cases of aspergillosis.

Comparison of two different PCR detection methods. Application to the diagnosis of pulmonary tuberculosis

The objectives are to assess the influence of the detection of the amplified DNA fragment on the sensitivity and specificity of the polymerase chain reaction (PCR). One hundred seventy-five sputum samples from 123 patients were processed. Sixty samples were taken from 60 subjects without tuberculosis, and the rest were taken from subjects with tuberculosis confirmed by culture. A fragment of the IS6110 sequence of Mycobacterium tuberculosis, which was detected using two different methods, was amplified. The detection methods used were a digoxigenin-labeled specific probe and chemiluminescent development and reamplification (nested PCR) combined with agarose gel electrophoresis. Sensitivity with probe detection was 75.65% and specificity 100%. Using the nested PCR technique, sensitivity rose to 93.04%, but specificity decreased to 96.6%. PCR is a quick and adequate way to diagnose pulmonary tuberculosis in cases where staining is negative yet there is a clinical suspicion of tuberculosis, even though a standardization process and large scale evaluation are still needed to determine its true usefulness.

Gene amplification in the diagnosis of mycobacterial infections

The number of importance of infections caused by Mycobacterium tuberculosis and other mycobacterial species is increasing. Since the detection and identification of mycobacteria by conventional laboratory methods (cultivation, staining, and biochemical tests) is a slow and complex procedure, rapid diagnostic methods are urgently needed. Several amplification methods based on different techniques have been applied in the detection of mycobacteria directly from clinical specimens. Most experience has been obtained from different polymerase chain reaction (PCR) assays and their general performance is good. However, their sensitivity in the analysis of samples containing small amounts of mycobacteria or samples containing inhibitory substances has been low. Furthermore, the risk of false positives caused by contamination is high, and the clinical relevance of the results may be unclear. Thus, these gene amplification techniques are a valuable adjunct to the diagnosis of mycobacteria, but so far they cannot replace conventional microbiological methods.

Evaluation of polymerase chain reaction for rapid diagnosis of clinically suspected tuberculous meningitis

SETTING

Since conventional bacteriological methods rarely detect Mycobacterium tuberculosis in cerebrospinal fluid (CSF) and are of limited use in the diagnosis of tuberculous meningitis (TBM), clinical features suggestive of TBM supported by indirect evidence such as CSF examination and computerized tomography (CT) of the head have been used for the early diagnosis of TBM.

OBJECTIVE

We evaluated the efficacy of polymerase chain reaction (PCR) in the diagnosis of TBM.

METHODS

Coded CSF samples from 40 patients with TBM and from 49 patients with other neurological disorders were processed. In the absence of a reliable sensitive and specific test for M. tuberculosis in CSF, we used a set of established clinical criteria as the gold standard. Accordingly, the patients were divided into definite, highly probable, probable and possible TBM. The samples were decoded only after completion of the laboratory tests.

RESULTS

PCR was positive in 2/4, 19/20, 13/16 patients with highly probable, probable and possible TBM respectively. None of the samples were positive by conventional bacteriological methods. However, 3/49 CSF samples from non-TBM patients were also found positive by PCR. PCR detected M. tuberculosis genomic DNA in the CSF of 85% of clinically suspected TBM cases and 6.1% of non-tuberculous controls.

CONCLUSION

PCR, along with the suggested clinical criteria, offers a rapid and fairly accurate diagnosis of TBM.