Multiplex PCR for rapid diagnosis of tuberculous meningitis

Recent advances in microbiological and molecular biological detection techniques of tuberculous meningitis

Tuberculous meningitis (TBM) is the most common type of central nervous system tuberculosis (TB) and has the highest mortality and disability rate. Early diagnosis is key to improving the prognosis and survival rate of patients. However, laboratory diagnosis of TBM is often difficult due to its paucibacillary nature and sub optimal sensitivity of conventional microbiology and molecular tools which often fails to detect the pathogen. The gold standard for TBM diagnosis is the presence of MTB in the CSF. The recognised methods for the identification of MTB are acid-fast bacilli (AFB) detected under CSF smear microscopy, MTB cultured in CSF, and MTB detected by polymerase chain reaction (PCR). Currently, many studies consider that all diagnostic techniques for TBM are not perfect, and no single technique is considered simple, fast, cheap, and efficient. A definite diagnosis of TBM is still difficult in current clinical practice. In this review, we summarise the current state of microbiological and molecular biological diagnostics for TBM, the latest advances in research, and discuss the advantages of these techniques, as well as the issues and challenges faced in terms of diagnostic effectiveness, laboratory infrastructure, testing costs, and clinical expertise, for clinicians to select appropriate testing methods.

Molecular diagnosis of Tuberculous meningitis: sdaA-based multi-targeted LAMP and GeneXpert Ultra

SETTING

Nucleic acid amplification techniques like GeneXpert and GeneXpert Ultra (Xpert Ultra), the first-line tests for diagnosing Tuberculous meningitis (TBM), are expensive and depend on sophisticated equipment.

OBJECTIVE

The diagnostic potential of multitargeted loop-mediated isothermal assay (MLAMP), a low-cost simple test using novel gene combination, was evaluated for TBM.

DESIGN

300 CSF specimen (200 TBM patients, 100 controls) processed between January 2017 and December 2021 were subjected to MLAMP (using sdaA, IS1081 and IS6110 gene targets), sdaA PCR and Xpert Ultra. The performance was evaluated against uniform case definition as per Marais criteria, and against culture.

RESULTS

Uniform case definition classified 50 as definite TBM and 150 as probable or definite TBM. Against this uniform case definition, the sensitivity and specificity of MLAMP was 88% and 100%, respectively. The sensitivity was 96% against culture-positive cases and 85.3% against culture-negative cases. The sensitivity of sdaA-LAMP, IS1081-LAMP, IS6110-LAMP, Xpert Ultra and sdaA-PCR was 82.5%, 80.5%, 85.3%, 67% and 71%, respectively against uniform case definition. sdaA-LAMP detected additional two cases and IS1081-LAMP detected nine. 11 of 134 (8.2%) cases were reported rifampicin resistant by Xpert Ultra.

CONCLUSION

MLAMP, incorporating sdaA and IS1081, is a cheap, easy and accurate first-line diagnostic test for TBM.

Comparison of Protein B Polymerase Chain Reaction (PCR) With IS6110 PCR for Diagnosis of Tuberculous Meningitis Patients

Purpose Tuberculous meningitis (TBM) is a diagnostic challenge. With the conventional staining and culture techniques being too insensitive and time-consuming, and the commercial detection systems being costly, polymerase chain reaction (PCR) seems lucrative for routine laboratories. The purpose of this study was to evaluate the diagnostic potential of protein b antigen polymerase chain reaction (Pab PCR) for TBM, in comparison to IS6110. Another purpose was to compute a cut-off at which adenosine deaminase (ADA) could diagnose TBM. Material and methods This is a prospective case-control study to measure the diagnostic accuracy of PCR, BACTEC culture, Lowenstein-Jensen (LJ) culture, ADA, and acid-fast bacilli (AFB) smear tests in TBM. CSF from 50 TBM patients (10 confirmed, 40 clinically suspected) and 40 controls was subjected to Pab PCR and IS6110 PCR, and performance was compared against culture and composite reference standards. Results The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of Pab PCR in diagnosing TBM were 82%, 100%, 100%, and 81.63%, respectively, and that of IS6110 PCR were 74%, 100%, 100%, and 75.47%, respectively. Both PCRs outperformed culture (p<0.001). Though performance of both PCRs was comparable (p=0.335) with excellent agreement (k=0.86), Pab PCR detected four additional cases, one culture-positive and three culture-negative clinically suspected. ADA of 6.5 IU/L was able to differentiate between TBM and non-TBM with 86% sensitivity and 63% specificity. Conclusions Molecular tools such as PCR have the potential to increase the clinician's ability to diagnose tuberculous meningitis. Pab PCR is a rapid and reliable method for diagnosing TBM in routine microbiology laboratories.

Advances in tuberculous meningitis diagnosis

Introduction: Tuberculous meningitis (TBM) is the most devastating form of central nervous system tuberculosis (TB) and causes high mortality worldwide. Nonspecific clinical manifestations and limited sensitivity of existing laboratory methods make the diagnosis elusive due to the paucibacillary nature of the infection. Areas Covered: We reviewed current literature on the adequacy and limitations of globally existing laboratory methods for diagnosing TBM. Expert opinion: TBM is deadliest among all TB forms, as the outcome may lead to death in 50% of cases, and survivors undergo irreversible neurological disorders. Therefore, early diagnosis and prompt treatment are cornerstones of effective disease management. Conventional microscopy and culture are widely used modalities but remain inadequate in most TBM cases. Although expanded use of rapid molecular tests such as real-time PCR and Xpert Ultra, even in resource-limited settings, hold promising results for TB diagnosis but need optimization for early detection of TBM. Moreover, CSF IGRA is also used but unable to differentiate between active and latent TB. Overall no single test for diagnosing TBM has adequate accuracy so, there is an urgent need to devise a point-of-care test.

Molecular diagnosis, genetic diversity and drug sensitivity patterns of Mycobacterium tuberculosis strains isolated from tuberculous meningitis patients at a tertiary care hospital in South India

Tuberculous meningitis (TBM) is the most severe form of Mycobacterium tuberculosis (Mtb) infection in humans and is a public health concern worldwide. We evaluated the performance of GeneXpert MTB/RIF (GeneXpert) for the diagnosis of TBM. In addition, genetic diversity and drug susceptibility profiling of Mtb strains isolated from TBM patients were also investigated. A total of 293 TBM suspected cerebrospinal fluid (CSF) samples were collected and subjected to GeneXpert and Mycobacterial Growth Indicator Tube (MGIT 960) culture, respectively. Sensitivity and specificity of GeneXpert was 72.7% and 98.5%, respectively by using MGIT 960 as a gold standard (GeneXpert (n = 20, 6.8%) vs MGIT 960 (n = 22, 7.5%)). All Mtb positive cultures were subjected to 24-locus Mycobacterial Interspersed Repetitive Unit Variable Number Tandem Repeat (MIRU-VNTR) typing, Line probe assay (LPA) and MGIT 960- Drug Susceptibility Testing (DST). The rpoB gene was amplified and sequenced for selected isolates. Among our TBM patients, East African Indian (EAI) lineage (n = 16, 72.7%) was most predominant followed by Beijing (n = 3, 13.6%), S-family (n = 2, 9.1%) and Delhi/CAS (n = 1, 4.5%). Three Mtb strains were found to be Isoniazid (INH) resistant by MGIT 960; however LPA revealed that two strains were INH resistant and one strain was multi drug resistant (MDR) (Resistant to Isoniazid and Rifampicin (RIF)). We identified rifampicin resistant isolate with the mutation D516F in rifampicin resistance-determining region (RRDR) and observed discordant results between LPA, GeneXpert and MGIT 960. In addition, GeneXpert showing false RIF resistance was identified (no mutation in RRDR). We conclude that GeneXpert is useful for the diagnostic confirmation of TBM; however a GeneXpert negative sample should be subjected to MGIT 960 culture or LPA to rule out TBM. EAI lineage was the most predominant among TBM patients in South India and associated with drug resistance. The discordance between GeneXpert, MGIT 960 and LPA with respect to rifampicin resistance has to be ruled out to avoid TB treatment failure or relapse.

Xpert MTB/RIF ultra for the diagnosis of tuberculous meningitis: A diagnostic accuracy study from India

SETTING

Studies evaluating Xpert MTB/RIF Ultra assay (Xpert Ultra) for diagnosing tuberculous meningitis (TBM) are scarce and have reported contrasting results in comparison to Xpert MTB/RIF assay (Xpert).

OBJECTIVE

To evaluate the performance of Xpert Ultra in diagnosing TBM and compare it with Xpert and multiplex polymerase chain reaction (MPCR).

DESIGN

Xpert Ultra was performed on 244 cerebrospinal fluid (CSF) samples: 56 definite TBM, 148 probable TBM and 40 non-TBM controls. 105/244 CSF samples were also subjected to Xpert and MPCR (IS6110, MPB64, protein B).

RESULTS

The overall sensitivity of Xpert Ultra in diagnosing TBM from 244 CSF samples was 72.05% (96.42% - definite TBM, 62.83% - probable TBM) with a specificity of 100%. 18 (12.24%) cases [8 definite TBM, 10 probable TBM] were reported rifampicin resistant (Rif^R) by Xpert Ultra and confirmed by rpoB sequencing. 60 (40.81%) cases [9 definite TBM, 51 probable TBM] were reported rifampicin indeterminate (Rif^I) by Xpert Ultra (all trace category), out of which 45 [8 definite, 37 probable) were rifampicin susceptible (Rif^S) and 5 probable cases were Rif^R on rpoB sequencing. Out of 105 CSF samples subjected to all three techniques, TBM was diagnosed in 70.66%, 28% and 88% by Xpert Ultra, Xpert and MPCR, respectively.

CONCLUSION

Xpert Ultra detected TBM with higher sensitivity than Xpert. Among trace category, constituting 40% of TBM cases, rpoB gene sequencing confirmed 5 Rif^R cases.

Diagnostic performance of real time PCR and MALDI-TOF in the detection of nontuberculous mycobacteria from clinical isolates

This study aimed to evaluate the performance of real-time PCR (qPCR) and MALDI-TOF for accurate and timely detection of nontuberculous mycobacterium (NTM) from clinical isolates. We collected fifty NTM suspected Mycobacteria Growth Indicator Tube (MGIT) cultures and analysed the diagnostic performance of qPCR and VITEK MS using Line Probe Assay (LPA) GenoType CM (Common Mycobacteria) as gold standard. The qPCR assays targeting 16S rRNA, ITS and IS6110 genes were developed for the identification of NTM and Mycobacterium tuberculosis complex (MTBC). LPA GenoType CM, a PCR technique targeting 23S rRNA gene, followed by reverse hybridization and line probe technology identified 90% of Mycobacterium species including M. fortuitum (16%,n = 8), M. intracellulare (10%,n = 5), M. gordonae (10%,n = 5), M. xenopi (4%,n = 2), M. scrofulaceum (4%,n = 2), Mycobacterium additional species (AS) (32%,n = 16) and MTBC (14%,n = 7), qPCR detected 80% of Mycobacterium species (NTM, 66% (n = 33) and MTBC, 14% (n = 7)) and MALDI-TOF, 52% (M. fortuitum (12%,n = 6), M. intracellulare (10%, n = 5), M. simiae (8%,n = 4), M. gordonae (8%,n = 4), and MTBC (14%,n = 7)). Sensitivity of qPCR and MALDI-TOF was 88.9% and 57.8%, respectively with 100% specificity. The combination of qPCR and MALDI-TOF remains an appropriate test for timely diagnosis of Mycobacterium species. This may eventually assist to detect the cases that may have been missed by phenotypic tests and enhance the NTM diagnosis capability to improve effective patient management.

Magnetic bead flocculation test: Improving the diagnosis of tuberculous meningitis (TBM) in low-resource settings

BACKGROUND

Despite several recent advances in detection techniques, there is still an unmet need for simple tests for the diagnosis of tuberculous meningitis (TBM). Therefore, in an effort towards developing a simple and rapid diagnostic test for resource-poor settings, we designed an assay in which magnetic bead flocculation test (MBF) was used to detect the amplified DNA. Multi-targeted (using two multicopy gene targets IS6110 and IS1081) loop-mediated isothermal amplification (MLAMP) was used for amplification.

METHODS

MLAMP-MBF assay was performed on CSF samples of 600 patients, out of which 120 were definite TBM (culture confirmed), 280 were probable TBM and 200 were non-TB controls, based on Marais's criteria. The performance of assay was evaluated by comparing the result of definite TBM with culture and that of probable TBM with composite reference standard consisting of clinical, microbiological(smear/culture) and radiological parameters.

RESULTS

The overall sensitivity of MLAMP-MBF (using any of the two gene targets) was 89.5% and specificity was 100%. The sensitivity was 96.6% (116/120) in diagnosing definite TBM and 86.4% (242/280) in diagnosing probable TBM. The sensitivity of IS1081 was 88% and that of IS6110 was 83% in diagnosing TBM. Specificity of both the gene targets was 100%. There were 20 cases positive only by IS1081 LAMP and 6 cases positive only by IS6110; thus 26 of 400 (6.5%) TBM cases could be additionally detected following multi-targeted approach.

CONCLUSION

MLAMP-MBF is a sensitive, robust, cost-effective and promising technique for diagnosis of TBM in low-resource high-endemic settings.

Comparative evaluation of loop-mediated isothermal amplification (LAMP) assay, GeneXpert MTB/Rif and multiplex PCR for the diagnosis of tubercular lymphadenitis in HIV-infected patients of North India

BACKGROUND

Tubercular lymphadenitis (TBLA) is one of the most common extrapulmonary manifestations of tuberculosis in patients with HIV. With several other pathological conditions presenting as lymphadenitis and lack of consensus regarding a gold standard test, the diagnosis of TBLA remains a challenge for the clinician.

OBJECTIVES

and design: In this study, we have assessed the potential of loop-mediated isothermal amplification (LAMP) test for the diagnosis of TBLA in HIV-infected patients. The study group included samples collected by fine needle aspiration (FNAC) of lymph nodes from 24 HIV-infected patients with TBLA. A composite reference standard was used to identify cases of TBLA based on clinical suspicion, results of cytology, AFB smear, MGIT culture, GeneXpert MTB/RIF, multiplex polymerase chain reaction (MPCR) and subsequently clinical response to antitubercular therapy. These tests were also carried out in 26 control samples of lymph node FNAC from HIV-infected patients with non-tubercular lymphadenitis.

RESULTS

LAMP assay was positive in 19/24 TBLA cases and yielded a sensitivity of 79.17% with 100% specificity. Cytology was suggestive in 18/24 (75%) TBLA cases. GeneXpert MTB/RIF assay correctly identified 16/24 TBLA cases, but the test did show one false positive result reducing its specificity. MPCR had the highest sensitivity of 91.67% as it correctly identified 22/24 cases and showed no false positive result.

CONCLUSION

The current study highlights the potential of LAMP test for the specific diagnosis of tubercular lymphadenitis in FNAC samples from HIV-infected patients, especially when cytology is either non-conclusive or non-available. Though MPCR had a higher sensitivity than LAMP assay, the added advantages of low cost, minimal technical expertise and simplicity of procedure make LAMP assay a suitable diagnostic test in resource-limited settings.

Clinical value of interferon-γ release assay in the diagnosis of active tuberculosis

Sensitivity and specificity of the interferon-γ release test for active tuberculosis screening were evaluated. Due to the high-test cost of imported IGRAs, QFT-GIT and T-SPOT.TB, we applied a cheaper domestic TB-IGRA which was approved in China recently. We recruited 740 patients and performed tuberculosis interferon release test (IGRAs), detection of Mycobacterium tuberculosis IgG antibody (TB-IgG) and tuberculin skin test (TST). The sensitivity of the three methods are 90.8, 40.0 and 75.45%, with specificity of 76.62, 74.47 and 72.27%. The area under the ROC curve according to the value of T-N detected by IGRAs was 0.878 (95% CI, 0.839–0.917), with the area under the curve for the diagnosis of active pulmonary tuberculosis and extrapulmonary tuberculosis being 0.839 and 0.841 respectively. The interferon-γ release test seems to be superior to TST and TB-IgG as a screening tool for the detection of active tuberculosis in China.

A Systematic Review and Meta-analysis of the Diagnostic Accuracy of Nucleic Acid Amplification Tests for Tuberculous Meningitis

The diagnosis of tuberculous meningitis (TBM) is difficult and poses a significant challenge to physicians worldwide. Recently, nucleic acid amplification (NAA) tests have shown promise for the diagnosis of TBM, although their performance has been variable. We undertook a systematic review and meta-analysis to evaluate the diagnostic accuracy of NAA tests with cerebrospinal fluid (CSF) samples against that of culture as the reference standard or a combined reference standard (CRS) for TBM. We searched the Embase, PubMed, Web of Science, and Cochrane Library databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures (i.e., sensitivity and specificity) were pooled with a random-effects model. All statistical analyses were performed with STATA (version 14 IC; Stata Corporation, College Station, TX, USA), Meta-DiSc (version 1.4 for Windows; Cochrane Colloquium, Barcelona, Spain), and RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark) software. Sixty-three studies comprising 1,381 cases of confirmed TBM and 5,712 non-TBM controls were included in the final analysis. These 63 studies were divided into two groups comprising 71 data sets (43 in-house tests and 28 commercial tests) that used culture as the reference standard and 24 data sets (21 in-house tests and 3 commercial tests) that used a CRS. Studies which used a culture reference standard had better pooled summary estimates than studies which used CRS. The overall pooled estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) of the NAA tests against culture were 82% (95% confidence interval [CI], 75 to 87%), 99% (95% CI, 98 to 99%), 58.6 (95% CI, 35.3 to 97.3), and 0.19 (95% CI, 0.14 to 0.25), respectively. The pooled sensitivity, specificity, PLR, and NLR of NAA tests against CRS were 68% (95% CI, 41 to 87%), 98% (95% CI, 95 to 99%), 36.5 (95% CI, 15.6 to 85.3), and 0.32 (95% CI, 0.15 to 0.70), respectively. The analysis has demonstrated that the diagnostic accuracy of NAA tests is currently insufficient for them to replace culture as a lone diagnostic test. NAA tests may be used in combination with culture due to the advantage of time to result and in scenarios where culture tests are not feasible. Further work to improve NAA tests would benefit from the availability of standardized reference standards and improvements to the methodology.

Multiplex Polymerase Chain Reaction for diagnosis of gastrointestinal tuberculosis

Background and Aim

To evaluate the role of multiplex polymerase chain reaction (PCR) for diagnosis of gastrointestinal tuberculosis (GITB).

Methods

This was a prospective observational study conducted from July 2015 to November 2016 at a tertiary care teaching institution in north India. Fifty individuals with clinically suspected GITB and older than 18 years of age were recruited. Patients underwent radiological investigations, esophagogastroduodenoscopy, or colonoscopy as clinically indicated. Multiple biopsies for tissue diagnosis and PCR were taken. All specimens were subjected to Ziehl Neelsen staining, histopathology, and multiplex PCR using specific primers for genes IS6110, MPB64, and Protein b. The performance of the assay was assessed using a composite reference standard for diagnosis of tuberculosis. It comprised a combination of clinical characteristics and microbiological methods, including smear, Bactenecin (BACTEC) culture, histopathology, and response to antitubercular therapy.

Results

A final diagnosis of tuberculosis was made in 32 cases (Duodenal‐4, Ileo‐colonic‐28). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of histopathology for the diagnosis of tuberculosis was 28.12, 100, 100, and 43.9%, respectively. The sensitivity, specificity, PPV and NPV of BACTEC Mycobacteria Growth Indicator Tube (MGIT) culture for the diagnosis of tuberculosis was 9.3, 100, 100, and 38.29%, respectively. The sensitivity, specificity, PPV, and NPV of multiplex PCR for the diagnosis of tuberculosis was 87.5, 100, 100, and 86.2%, respectively.

Conclusion

Multiplex PCR using specific primers for genes IS6110, MPB64, and Protein b had a higher sensitivity compared to conventional techniques for the diagnosis of GITB.

Comparative evaluation of Xpert MTB/RIF assay with multiplex polymerase chain reaction for the diagnosis of tuberculous meningitis

BACKGROUND

Rapid and specific diagnosis of tuberculous meningitis (TBM) is of paramount importance to decrease morbidity and mortality. Therefore, the present study was undertaken to compare the efficacy of Xpert MTB/RIF assay (GXpert) and multiplex PCR (MPCR) using three targets (IS6110, MPB64 and protein B) for diagnosing tuberculous meningitis.

METHODS

GXpert and MPCR were performed on cerebrospinal fluid samples of 225 patients out of which 80 were culture-positive confirmed cases of TBM, 100 were 'suspected' cases of TBM and 45 were non-TBM controls. rpoB gene sequencing was done for diagnosing rifampicin (Rif) resistance in all positive cases.

RESULTS

GXpert and MPCR were positive in 91/180 (50.5%) and 157/180 (87.2%) confirmed or suspected TBM patients respectively. Both the tests were negative in all 45 controls. Rif resistance was detected in 14 cases by GXpert and in 13 cases by MPCR. Rif resistance was confirmed in 13 cases with rpoB gene sequencing. There was one case of false Rif resistance detected by GXpert which was Rif susceptible on rpoB gene sequencing. Cost of doing MPCR was less than USD1 whereas GXpert required USD10 per isolate.

CONCLUSION

MPCR has a higher sensitivity than GXpert for diagnosing TBM. MPCR is a robust and cost effective method for diagnosis of TBM in low-resource and high-endemic countries.

Rare Clinical Presentation of Tuberculous Meningitis: A Case Report

Introduction

Tuberculosis is the second leading cause of death under the category of infectious diseases, after the human immunodeficiency virus (HIV). Tuberculous meningitis (TBM) constitutes about 5% of all extrapulmonary disease worldwide. This report describes a case of Tuberculous meningitis with rare presentation in a 28-year-old woman, who was treated based on a collection of her social background, clinical findings and Multiplex PCR of tuberculosis.

Case presentation

A 28-year-old Malay woman with no significant medical history presented to HUSM with one month history of on and off fever, two weeks history of generalised limbs weakness and one week history of dysphagia. She was reported to have experienced visual hallucination and significant weight loss. Her laboratory result is significant for leukocytosis, elevated ESR and hypernatremia. Non-enhanced and contrast CT scan of the brain showed severe bilateral frontal cerebral atrophy. Cerebral spinal fluid (CSF) for multiplex PCR for Mycobacterium tuberculosis complex was positive. She was promptly started on anti-TB regime combined with dexamethasone. Subsequent follow-up showed significant improvement.

Conclusion

This is a rare clinical manifestation of Tuberculous meningitis that demonstrates the importance of recognising and initiating the treatment early to reduce disabilities and improve clinical outcome.

Facial Weakness, Diplopia, and Fever in a 31-Year-Old: An Atypical Case of Tuberculous Meningitis

Tuberculous meningitis (TBM) is an infection of the central nervous system (CNS) meninges that carries high morbidity and mortality. It is important to recognize, as patients may present with atypical symptoms. We describe the case of a 31-year-old man with a history of diabetes who presented with a sub-acute onset of right-sided facial weakness and right gaze difficulty with diplopia. History revealed low-grade fever, right-sided headache, fatigue and moderate weight loss for the past several weeks. The patient did not report neck stiffness, rigidity, fever, chills or cough. The physical exam revealed sixth nerve palsy with a right Horner’s syndrome. Magnetic resonance imaging (MRI) of the brain showed pachymeningeal enhancement. A spinal tap revealed elevated white blood cells (WBCs), glucose and protein; cerebrospinal fluid (CSF) culture showed Mycobacterium tuberculosis. The patient was diagnosed with TBM and treated with isoniazid, rifampin, pyrazinamide, ethambutol and vitamin B6 for 12 months.

The timely diagnosis of TBM can be challenging due to a nonspecific clinical presentation. In patients with a sub-acute onset of headache, fever and meningeal signs, TBM should be considered in the differential. If suspected, treatment should be initiated immediately to prevent further neurological impairment and death.

Novel approach based on one-tube nested PCR and a lateral flow strip for highly sensitive diagnosis of tuberculous meningitis

Rapid and sensitive detection of Mycobacterium tuberculosis (M. Tb) in cerebrospinal fluid is crucial in the diagnosis of tuberculous meningitis (TBM), but conventional diagnostic technologies have limited sensitivity and specificity or are time-consuming. In this work, a novel, highly sensitive molecular diagnostic method, one-tube nested PCR-lateral flow strip test (OTNPCR-LFST), was developed for detecting M. tuberculosis. This one-tube nested PCR maintains the sensitivity of conventional two-step nested PCR and reduces both the chance of cross-contamination and the time required for analysis. The PCR product was detected by a lateral flow strip assay, which provided a basis for migration of the test to a point-of-care (POC) microfluidic format. The developed assay had an improved sensitivity compared with traditional PCR, and the limit of detection was up to 1 fg DNA isolated from M. tuberculosis. The assay was also specific for M. tuberculosis, and no cross-reactions were found in other non-target bacteria. The application of this technique to clinical samples was successfully evaluated, and OTNPCR-LFST showed 89% overall sensitivity and 100% specificity for TBM patients. This one-tube nested PCR-lateral flow strip assay is useful for detecting M. tuberculosis in TBM due to its rapidity, high sensitivity and simple manipulation.

RNomic identification and evaluation of npcTB_6715, a non-protein-coding RNA gene as a potential biomarker for the detection of Mycobacterium tuberculosis

Technological advances in RNA biology greatly improved transcriptome profiling during the last two decades. Besides the discovery of many small RNAs (sRNA) that are involved in the physiological and pathophysiological regulation of various cellular circuits, it becomes evident that the corresponding RNA genes might also serve as potential biomarkers to monitor the progression of disease and treatment. sRNA gene candidate npcTB_6715 was previously identified via experimental RNomic (unpublished data), and we report its application as potential biomarker for the detection of Mycobacterium tuberculosis (MTB) in patient samples. For proof of principle, we developed a multiplex PCR assay and report its validation with 500 clinical cultures, positive for Mycobacteria. The analysis revealed 98.9% sensitivity, 96.1% specificity, positive and negative predictive values of 98.6% and 96.8%, respectively. These results underscore the diagnostic value of the sRNA gene as diagnostic marker for the specific detection of MTB in clinical samples. Its successful application and the general ease of PCR‐based detection compared to standard bacterial culture techniques might be the first step towards ‘point‐of‐care’ diagnostics of Mycobacteria. To the best of our knowledge, this is the first time for the design of diagnostic applications based on sRNA genes, in Mycobacteria.

Multiplex PCR as a novel method in the diagnosis of spinal tuberculosis-a pilot study

BACKGROUND

Establishment of a reliable and rapid diagnosis is of paramount importance in spinal tuberculosis. The available gadgetry of investigations, such as AFB smear, culture of Mycobacterium tuberculosis, and Uniplex PCR, suffers from a lack of adequate sensitivity and/or a lack of rapidity. Therefore, many times a diagnosis is made either very late in the disease process or sometimes empirical therapy has to be started because a definite diagnosis could not be made. All of these are not ideal situations for a clinician. The present study was done with the aim to establish a rapid and reliable diagnosis of M. tuberculosis infection. This was established by identifying M. tuberculosis genes.

METHODS

The study was done on nine consecutive patients who presented with non-traumatic spontaneous vertebral compression collapse. CT-guided aspirate from the involved vertebra was subjected to Multiplex PCR (MPCR) using three primers: IS6110, protein b, and MPB 64. The aspirate was also subjected to smear and culture. The results of MPCR were compared with the final diagnosis.

RESULTS

Seven out of nine patients had a final diagnosis of tuberculosis. MPCR was positive in six of these seven patients, thus showing sensitivity of 85.7% and specificity of 100%. Results of MPCR were obtained within 24 h.

CONCLUSIONS

MPCR using IS6110, protein b, and MPB64 primers has a high sensitivity and specificity in rapid diagnosis of spinal tuberculosis. To the best of our knowledge, this has not been attempted before in spinal tuberculosis. This is particularly useful for paucibacillary infections like spinal tuberculosis. However, further studies using large sample sizes are needed to confirm the practical applicability of this technique.

Evaluation of polymerase chain reaction in space-occupying lesions of liver reported as granulomatous inflammation/tuberculosis on fine-needle aspiration cytology

Background:

Tubercular involvement of the liver is uncommon, but is a serious consideration in differential diagnosis of granulomatous conditions, especially in endemic regions like India.

Objective:

To assess the role of polymerase chain reaction (PCR) done on archival cytological material in diagnosing tuberculosis (TB) in cases reported as granulomatous inflammation/TB in liver lesions.

Materials and Methods:

This was a retrospective study including a total of 17 cases of liver space-occupying lesions (SOLs) reported as granulomatous inflammation (n = 12) and TB (n = 5). The smears were retrieved from the archives of the department and were reviewed for the cytomorphologic features. Air-dried smears stained with May–Grünwald–Giemsa (MGG) stain were assessed for the representative material in the form of epithelioid granulomas and giant cells. One/two MGG smears from each case were destained and the material was used for performing PCR for Mycobacterium tuberculosis by amplification of 123 bp fragment of the IS6110 insertion element.

Results:

The age of the patients ranged from 3 to 61 years. There were 12 females and 5 males. The patients presented with solitary/multiple liver SOLs. DNA could be extracted from 10/17 cases from archival MGG smears. PCR positivity was noted in 8/10 cases (including four acid-fast bacilli smear-positive cases), confirming a diagnosis of TB.

Conclusion:

Cytomorphology alone may not be sufficient for differentiating various granulomatous lesions reported in liver SOLs. DNA can be extracted from the archival cytological MGG-stained smears. PCR should be carried out if Ziehl–Neelsen staining is negative in granulomatous lesions, especially when material has not been submitted for culture.

Diagnostic potential of multi-targeted LAMP (loop-mediated isothermal amplification) for osteoarticular tuberculosis

Delay in diagnosing osteoarticular tuberculosis (OATB) contributes significantly to morbidity by causing disfiguration and neurological sequelae. The delay caused by conventional culture and the expertise and expense involved in other nucleic acid based tests, make LAMP (loop-mediated isothermal amplification) assay a favorable middle path. We evaluated LAMP assay using IS6110 and MPB64 for rapid diagnosis of OATB by comparing with IS6110 PCR and culture. LAMP assay was performed on 140 synovial fluid and pus samples (10 culture-positive proven cases, 80 culture-negative probable cases, and 50 negative controls) using three set of primer pairs each for IS6110 and MPB64. LAMP assay, using two-target approach, had an overall sensitivity and specificity of 90% and 100% in detecting OATB. Sensitivity of IS6110 PCR, IS6110 LAMP, and MPB64 LAMP was 80%, 100%, and 100%, respectively, for confirmed cases and 72.5%, 81.75%, and 86.25%, respectively, for probable cases. Six additional cases were picked using two-target approach. LAMP assay utilizing IS6110 and MPB64 is a cost-effective technique for an early and reliable diagnosis of OATB. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:361-365, 2017.

Cerebral hemorrhage due to tuberculosis meningitis: a rare case report and literature review

Tuberculosis (TB) is a common disease to threaten human health. TB of the central nervous system (CNS) is rare but the most serious type of systemic TB because of its high mortality rate, serious neurological complications and sequelae. In this case report, we describe a woman who presented with walking instability, intracerebral hemorrhage and leptomeningeal enhancement due to tuberculosis meningitis. The patient had no significant medical history and the initial clinical symptoms were walking instability. On analysis, the cerebrospinal fluid was colorless and transparent, the pressure was more than 400 mm H₂O, there was lymphocytic pleocytosis, increased protein, and decreased glucose levels present. No tuberculosis or other bacteria were detected. The patient's brain computed tomography image showed intra-cerebral hemorrhage (ICH) and contrast magnetic resonance imaging showed ICH in the right frontal lob, and leptomeningeal enhancement. CNS TB is rare but has a high mortality rate. As this disease has no unique characteristics at first presentation such as epidemiology and obvious clinical manifestation, a diagnosis of CNS TB remains difficult.

Psychosis secondary to tuberculosis meningitis

We report a case of a 19-year-old immunocompetent Malay woman who presented with a worsening psychotic disorder of 1-year duration. She initially presented with social isolation with subsequent mutism and stupor. Physical examination revealed a stuporous, emaciated, dehydrated woman with Glasgow Coma Scale of 11/15 (E4V2M5). She had a blank stare, mutism and akinesia. Motor examination revealed upper motor neuron findings. Neck stiffness was present, however, Kernig's and Brudzinski's signs were negative. There were no other findings on other systems. Brain imaging and EEG were normal. Cerebrospinal fluid investigations revealed positive cerebrospinal fluid Mycobacterium tuberculosis PCR (MTB PCR). The patient was treated with empirical antituberculosis drugs and steroids. On follow-up visit 1 month later, her psychotic symptoms had fully resolved. She was able to ambulate and care for herself; she was unable to recall the symptoms she had experienced before and during admission.

Utility of adenosine deaminase (ADA), PCR & thoracoscopy in differentiating tuberculous & non-tuberculous pleural effusion complicating chronic kidney disease

Background & objectives:

Pleural effusion is a common occurrence in patients with late-stage chronic kidney disease (CKD). In developing countries, many effusions remain undiagnosed after pleural fluid analysis (PFA) and patients are empirically treated with antitubercular therapy. The aim of this study was to evaluate the role of adenosine deaminase (ADA), nucleic acid amplification tests (NAAT) and medical thoracoscopy in distinguishing tubercular and non-tubercular aetiologies in exudative pleural effusions complicating CKD.

Methods:

Consecutive stage 4 and 5 CKD patients with pleural effusions underwent PFA including ADA and PCR [65 kDa gene; multiplex (IS6110, protein antigen b, MPB64)]. Patients with exudative pleural effusion undiagnosed after PFA underwent medical thoracoscopy.

Results:

All 107 patients underwent thoracocentesis with 45 and 62 patients diagnosed as transudative and exudative pleural effusions, respectively. Twenty six of the 62 patients underwent medical thoracoscopy. Tuberculous pleurisy was diagnosed in six while uraemic pleuritis was diagnosed in 20 subjects. The sensitivity and specificity of pleural fluid ADA, 65 kDa gene PCR, and multiplex PCR were 66.7 and 90 per cent, 100 and 50 per cent, and 100 and 100 per cent, respectively. Thoracoscopy was associated with five complications in three patients.

Interpretation & conclusions:

Uraemia remains the most common cause of pleural effusion in CKD even in high TB prevalence country. Multiplex PCR and thoracoscopy are useful investigations in the diagnostic work-up of pleural effusions complicating CKD while the sensitivity and/or specificity of ADA and 65 kDa gene PCR is poor.

Simultaneous Detection of Five Pathogens from Cerebrospinal Fluid Specimens Using Luminex Technology

Early diagnosis and treatment are crucial for the outcome of central nervous system (CNS) infections. In this study, we developed a multiplex PCR-Luminex assay for the simultaneous detection of five major pathogens, including Mycobacterium tuberculosis, Cryptococcus neoformans, Streptococcus pneumoniae, and herpes simplex virus types 1 and 2, which frequently cause CNS infections. Through the hybridization reaction between multiplex PCR-amplified targets and oligonucleotide “anti-TAG” sequences, we found that the PCR-Luminex assay could detect as low as 10¹–10² copies of synthetic pathogen DNAs. Furthermore, 163 cerebrospinal fluid (CSF) specimens from patients with suspected CNS infections were used to evaluate the efficiency of this multiplex PCR-Luminex method. Compared with Ziehl-Neelsen stain, this assay showed a high diagnostic accuracy for tuberculosis meningitis (sensitivity, 90.7% and specificity, 99.1%). For cryptococcal meningitis, the sensitivity and specificity were 92% and 97.1%, respectively, compared with the May Grunwald Giemsa (MGG) stain. For herpes simplex virus types 1 and 2 encephalitis, the sensitivities were 80.8% and 100%, and the specificities were 94.2% and 99%, respectively, compared with Enzyme Linked Immunosorbent Assay (ELISA) assays. Taken together, this multiplex PCR-Luminex assay showed potential efficiency for the simultaneous detection of five pathogens and may be a promising supplement to conventional methods for diagnosing CNS infections.

Clinical features, Outcomes and Molecular Profiles of Drug Resistance in Tuberculous Meningitis in non-HIV Patients

Tuberculous meningitis continues to be a serious problem for physicians because it is difficult to make an early diagnosis and the consequences of delaying treatment are severe. The objective of this study is to provide data for the optimization of diagnostic and timely treatment of tuberculous meningitis. Of the 401 human immunodeficiency virus (HIV)-negative tuberculous meningitis patients in our study, 332 were found to have an impaired blood brain barrier (82.8%). Nearly 17.0% of patients failed to be timely diagnosed. Headache (53.6%) and fever (48.6%) were the most common features, and Computed Tomography/Magnetic Resonance Imaging (CT/MRI) detected 96 patients (23.9%) with abnormal meningeal imaging. Cerebrospinal fluid real-time polymerase chain reaction was positive in 73.8% of the tuberculous meningitis patients, whereas, smears and cultures detected only 6.7% and 5.2%, respectively. Further analysis identified striking differences between drug-resistant and drug-susceptible tuberculous meningitis. Patients with drug resistance correlated with grave prognosis. Tuberculous meningitis diagnosis should overall embody clinical symptoms, laboratory and cerebral imaging findings, and more sensitive diagnostic approaches are still warranted. Our data suggest cerebrospinal fluid polymerase chain reaction for mycobacterial DNA and molecular drug susceptibility testing as routine assays for suspected tuberculous meningitis patients, and observation of the blood brain barrier function could be performed for individual management.

Detection of Mycobacterium tuberculosis Genome in Subretinal Fluid of Patients with Latent Tuberculosis Infection

PURPOSE

To test our hypothesis that Mycobacterium tuberculosis (MTB) DNA may be present in retinal pigment epithelium (RPE) cells in individuals with latent tuberculosis (TB) infection.

METHODS

A total of 100 patients with rhegmatogenous retinal detachment (without any signs of endogenous uveitis in either eye) underwent pars plana vitrectomy (PPV) with internal tamponade. All were subjected to tuberculin skin test. None had manifest systemic TB disease. The subretinal fluid collected during surgery was subjected to multitargeted polymerase chain reaction (PCR) targeting three genes of MTB (IS6110, MPB64 and protein b).

RESULTS

In total, 16 patients had latent TB, of which TB PCR was positive in six patients.

CONCLUSIONS

We demonstrate presence of MTB genome in the subretinal fluid containing RPE cells from individuals with latent TB infection, who did not have any evidence of intraocular TB or manifest systemic TB disease, and suggest that MTB can be sequestrated in the RPE cells in latent TB.

Etiological diagnosis of granulomatous tubulointerstitial nephritis in the tropics

Background

Granulomatous tubulointerstitial nephritis (GIN) is common due to infections, drugs or sarcoidosis. However, the cause is often difficult to establish and the studies are limited. We studied the etiology of GIN and compared the clinical and histological features and outcome in different etiologies at a tertiary care center in North India.

Methods

Renaö biopsies from GIN cases diagnosed from January 2004 to April 2014 were retrieved. Stain for acid fast bacilli was performed in all biopsies. Etiological diagnosis was based on clinical features, extra-renal manifestations, radiology, history of drug intake and demonstration of infective agent. Tissue PCR for tubercular DNA was performed in seven biopsies.

Results

Seventeen GIN patients [mean age 35 ± 15 years; males 11] were identified. Tuberculosis was the commonest etiology followed by idiopathic, sarcoidosis and fungal. Both tuberculosis and sarcoidosis patients presented with subnephrotic proteinuria and raised serum creatinine. Acid fast bacilli were demonstrated in 1/9 and necrosis was demonstrated in 3/9 granulomas in tuberculosis. Tissue PCR for tubercular DNA was positive in six TB patients and negative in one sarcoidosis patient. Patients responded well to appropriate therapy.

Conclusion

Etiological diagnosis of GIN is essential for timely and appropriate therapy. Tuberculosis is the commonest etiology (53%) in the tropics. Necrosis in granuloma, demonstration of acid fast bacilli, blood interferon gamma release assay and urine culture is not sensitive for the diagnosis of tuberculosis in GIN. Our findings suggest that tissue PCR for tuberculosis performed in an appropriate clinical setting is useful in the diagnostic evaluation of GIN.

rpoB gene high-resolution melt curve analysis: a rapid approach for diagnosis and screening of drug resistance in tuberculous meningitis

Timely and rapid diagnosis of multidrug resistance in tuberculous meningitis (TBM) is a challenge both for a microbiologist and neurologist. The present study was conducted to evaluate role of real-time polymerase chain reaction (PCR) using rpoB, IS6110, and MPB64 as targets in diagnosis of TBM in 110 patients and subsequent high-resolution melt (HRM) curve analysis of rpoB gene amplicons for screening of drug resistance. The sensitivity of smear, culture, and real-time PCR was 1.8%, 10.9%, and 83.63%, respectively. All 120 control patients showed negative results. With HRM rpoB analysis, rifampicin resistance was detected in 3 out of 110 cases of TBM (3.33%). Subsequently, results of HRM analysis were confirmed by rpoB gene sequencing, and mutations were observed at 516 (2 patients) and 531 (1 patient) codons, respectively. rpoB HRM analysis can be a promising tool for rapid diagnosis and screening of drug resistance in TBM patients in 90minutes.

Development and evaluation of a rapid multiplex-PCR based system for Mycobacterium tuberculosis diagnosis using sputum samples

Global tuberculosis (TB) control and eradication is hampered by the unavailability of simple, rapid and affordable diagnostic tests deployable at low infrastructure microscopy centers. We have developed and evaluated the performance of a nucleic acid amplification test for detection of Mycobacterium tuberculosis (MTB), the NWU-TB test, in clinical sputum specimens from 306 patients with suspected pulmonary tuberculosis. The test involves sputum sample processing using a Lyser device within 7 min, followed by rapid multiplex-PCR on a fast thermal cycler within 25 min, and amplicon resolution on agarose gel electrophoresis. Samples were also examined for presence of MTB using smear microscopy, GeneXpert and MGIT culture. Results were assessed in comparison to a MGIT culture as gold standard. Of the 306 patients, 174 had a previous TB history or already on treatment, and 132 were TB naïve cases. The NWU-TB system was found to have an overall sensitivity and specificity of 80.8% (95% CI: 75-85.7) and 75.6% (95% CI: 64.9-84.4) respectively, in comparison to 85.3% (95% CI: 79.9-89.6) and 73.2% (95% CI: 62.2-82.4) respectively for GeneXpert; and 62.1% (95% CI: 55.3-68.4) and 56.1% (95% CI: 44.7-67) respectively for smear microscopy. The study has shown that the NWU-TB system allows detection of TB in less than two hours and can be utilized at low infrastructure sites to provide quick and accurate diagnosis at a very low cost.

Evaluation of multiplex polymerase chain reaction utilising multiple targets in Mycobacterium tuberculosis direct test negative but culture positive cases: a potential method for enhancing the diagnosis of tuberculosis

PURPOSE

To evaluate multiplex Polymerase Chain Reaction (MPCR) utilising multiple targets (IS6110, Protein b [Pab] and MPB64 genes) in Mycobacterium tuberculosis Direct Test (MTD) negative but culture positive cases and comparison of MPCR with Real-Time polymerase chain reaction (RT-PCR) for diagnosis of tuberculosis.

MATERIALS AND METHODS

MPCR was carried out on 28 culture positive sputum samples. Out of 28 culture positive samples, 17 were originally reported, as MTD test negative and 11 were MTD test positive, respectively. The results of MPCR were compared with RT-PCR. To check the specificity of the tests, MPCR and RT-PCR were also evaluated with 16 non-tuberculous mycobacterial (NTM) isolates.

RESULTS

Out of 28 culture positive sputum samples, MPCR was positive in all 28/28 samples, whereas RT-PCR was positive in 27/28 samples and MTD test was originally tested positive in six sputum samples and on repeating MTD testing, five more sputum samples were positive and thus total number of MTD positive were 11/28 sputum samples, respectively. All the tests were negative on evaluation with all the 16 NTMs, thus giving specificity of 100% to all the tests; sensitivity of MPCR, RT-PCR and MTD tests were 100%, 96.42% and 39.28%, respectively, in these specifically selected samples.

CONCLUSIONS

MPCR may be an important tool in the rapid diagnosis of tuberculosis especially in disease endemic, resource limited countries.

Inflammatory optic disc edema due to Sarcoidosis mimicking malignant hypertension

A common ocular manifestation of sarcoidosis is anterior uveitis. Posterior uveitis is uncommon and optic disc edema is rare. We report one such case in which the initial presentation was mimicking malignant hypertension as the patient had a recent record of high blood pressure. However, the painful progressive vision loss due to optic disc edema, along with anterior uveitis, and histological proof of non-caseating granulomas on transbronchial lung biopsy clinched the diagnosis of ocular sarcoidosis. There was complete resolution of signs and symptoms with institution of steroids. There was also probable cardiac involvement. This case highlights the fact that all disc edemas in a diabetic and hypertensive patients is not just due to malignant hypertension, even if there is a recent history of elevated blood pressure.

Factors influencing polymerase chain reaction outcomes in patients with clinically suspected ocular tuberculosis

Background

Polymerase chain reaction (PCR) assay can be a useful method for definitive diagnosis in paucibacillary infections such as ocular tuberculosis (TB). In this study, we have evaluated factors affecting PCR outcomes in patients with clinically suspected ocular TB. Patients with clinically suspected ocular TB were investigated by PCR of aqueous or vitreous samples. Three control groups were also tested: group 1 included culture-proven non-tuberculous endophthalmitis, group 2 culture-negative non-tuberculous endophthalmitis, and group 3 patients undergoing surgery for uncomplicated cataract. PCR targeted one or more of following targets: IS6110, MPB64, and protein b genes of Mycobacterium tuberculosis complex. Multiple regression analysis (5% level of significance) was done to evaluate the associations between positive PCR outcome and laterality of disease, tuberculin skin test (TST)/interferon-gamma release assay (IGRA), chest radiography, and type of sample (aqueous or vitreous). The main outcome measures were positive PCR by one or more gene targets, and factors influencing positive PCR outcomes.

Results

All 114 samples were tested for MPB64, 110 for protein b, and 88 for IS6110. MPB64 was positive in 70.2% (n = 80) of tested samples, protein b in 40.0% (n = 44), and IS6110 in only 9.1% (n = 8). DNA sequencing of amplicons from four randomly chosen PCR reactions showed homology for M. tuberculosis complex. Of the 80 PCR-positive patients, 71 completed a full course of antitubercular therapy, of which 65 patients (91.5%) had complete resolution of inflammation at final follow-up. Among controls, 12.5% (3 out of 24) in group 1 and 18.7% (6 out of 32) in group 2 also tested positive by PCR. No PCR-positive outcome was observed in control group 3 (n = 25). Multiple regression analysis revealed significant association of positive PCR outcome with bilateral presentation, but not with a positive TST/IGRA, chest radiography, or type of sample (aqueous/vitreous) used.

Conclusions

Careful selection of gene targets can yield high PCR positivity in clinically suspected ocular TB. Bilateral disease presentation but not any evidence of latent systemic TB influences PCR outcomes. False-positive results may be seen in ocular inflammation unrelated to ocular TB.

Commercial nucleic acid amplification tests in tuberculous meningitis--a meta-analysis

Although nucleic acid amplification tests (NAATs) promise a rapid, definitive diagnosis of tuberculous meningitis, the performance of first-generation NAATs was suboptimal and variable. We conducted a meta-analysis of studies published between 2003 and 2013, using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool to evaluate methodological quality. The diagnostic accuracy of newer commercial NAATs was assessed. Pooled estimates of diagnostic accuracy for commercial NAATs measured against a cerebrospinal fluid Mycobacterium tuberculosis culture-positive gold standard were sensitivity 0.64, specificity 0.98, and diagnostic odds ratio 64.0. Heterogeneity was limited; P value = 0.147 and I(2) = 33.85%. The Xpert MTB/RIF® test was evaluated in 1 retrospective study and 4 prospective studies, with pooled sensitivity 0.70 and specificity 0.97. The QUADAS-2 tool revealed low risk of bias, as well as low concerns regarding applicability. Heterogeneity was pronounced among studies of in-house tests. Commercial NAATs proved to be highly specific with greatly reduced heterogeneity compared to in-house tests. Sub-optimal sensitivity remains a limitation.

Decrease in the incidence of culture-positive meningitis and cerebral tuberculomas in France from 1990 to 2007

We evaluated the incidence rate of culture-positive central nervous system tuberculosis (CNS TB) in France in 2007 and its time trend between 1990 and 2007. We used a capture–recapture analysis by using data recorded in 2007 by the mandatory notification system and the national network of the National Reference Centre (NRC). The 2007 sensitivity of the NRC was 79·4%. The previous sensitivity for 2000 (75·6%) and that for 2007 yielded a pooled estimate of 77·4% (95% confidence interval 64·8–88·0), which was used to extrapolate the number of culture-positive CNS TB cases from those reported in four surveys (1990, 1995, 2000, 2007). The extrapolated number of culture-positive CNS TB cases fell from 90 to 35 between 1990 and 2007, and the extrapolated incidence rates fell from 1·6 to 0·55 cases/million (P < 0·001). This favourable trend should be closely monitored following the change of the BCG vaccination policy in 2007.

Multiplex PCR for rapid diagnosis of gastrointestinal tuberculosis

Background:

Rapid and specific diagnosis of gastrointestinal tuberculosis (GITB) is of utmost importance.

Aim:

To evaluate Multiplex PCR (MPCR) using MPB64 and IS6110 primers specific for M. tuberculosis for rapid diagnosis of GITB.

Materials and Methods:

MPCR was performed on colonoscopy biopsy specimens on 11 GITB confirmed (culture/AFB/histopathology was positive), 29 GITB suspected and 30 Non GITB (control group) patients.

Results:

MPB64 PCR had sensitivity and specificity of 90% and 100% for confirmed GITB cases. In 29 clinically diagnosed but unconfirmed GITB cases, MPCR was positive in 72.41%. MPCR was negative in all control group patients. The overall sensitivity and specificity of microscopy, culture, histopathology and MPCR was 5%, 2% 20% and 77.5% and 100%, 100%, 100% and 100% respectively.

Conclusion:

MPCR has good sensitivity and specificity in diagnosing gastrointestinal tuberculosis.

Novel multi-targeted polymerase chain reaction for diagnosis of presumed tubercular uveitis

Background

The objective of this study was to report the use of multi-targeted polymerase chain reaction (PCR) in the diagnosis of presumed tubercular uveitis. Multi-targeted PCR using three targets specific for Mycobacterium tuberculosis, i.e., IS6110, MPB64, and protein b, was performed on intraocular fluid samples of 25 subjects. Nine had presumed tubercular uveitis, six had intraocular inflammation secondary to a nontubercular etiology (disease controls), and ten had no evidence of intraocular inflammation (normal controls). As described previously, response to antitubercular therapy was considered as the gold standard.

Results

Multi-targeted PCR was positive in seven out of nine patients with presumed tubercular uveitis and negative in all normal and disease controls. The sensitivity and specificity were 77.77% and 100%, respectively. For the diagnosis of presumed tubercular uveitis, multi-targeted PCR had a positive predictive value of 100% and a negative predictive value of 88.88%.

Conclusion

Multi-targeted PCR can be a valuable tool for diagnosing presumed tubercular uveitis.

Comparison of real time IS6110-PCR, microscopy, and culture for diagnosis of tuberculous meningitis in a cohort of adult patients in Indonesia

BACKGROUND

Bacteriological confirmation of tuberculous (TB) meningitis is difficult. Culture is slow and microscopy has insufficient sensitivity. We evaluated real time PCR targeting insertion sequence IS6110 among 230 consecutive adult patients with subacute meningitis in a referral hospital in Indonesia.

METHODS

Cerebrospinal fluid (CSF) samples were examined using microscopy, solid and liquid culture, and real time IS6110-PCR with a fluorescence-labeled probe using DNA extracted from CSF. CSF samples from 40 non-infectious neurology patients were used as negative controls. IS6110-PCR results were linked with clinical and CSF characteristics.

RESULTS

Most patients presented with subacute meningitis, after a median of 14 days of symptoms (range 7-30). After exclusion of cryptococcal and bacterial meningitis, 207 patients were classified as definite or probable TB meningitis; 17.9% with HIV infection. Among this group IS6110-PCR gave the highest positivity rate (68%, 95% CI 62-74%) compared with microscopy of ZN-stained slides (11%, 95% CI 7-15%), and mycobacterial culture using solid (36%, 95% CI 29-42%) and liquid (44%, 95% CI 37-51%) media. IS6110-PCR was positive in 92% of patients with culture-positive and 42% of patients with culture-negative probable TB meningitis. Among culture-negative patients, a positive PCR was associated with a history of TB treatment, a longer duration of illness, a higher CSF cell count and protein, and a lower CSF glucose. IS6110-PCR was negative in all CSF samples from non-meningitis control patients.

CONCLUSIONS

Real time IS6110-PCR is a quick, sensitive, and specific test for diagnosing of TB meningitis in this setting. Its performance in other (less-developed) settings needs further study.

Diagnosis of extrapulmonary tuberculosis by PCR

During the last two decades, the resurgence of tuberculosis (TB) has been documented in both developed and developing nations, and much of this increase in TB burden coincided with human immunodeficiency virus (HIV) epidemics. Since then, the disease pattern has changed with a higher incidence of extrapulmonary tuberculosis (EPTB) as well as disseminated TB. EPTB cases include TB lymphadenitis, pleural TB, TB meningitis, osteoarticular TB, genitourinary TB, abdominal TB, cutaneous TB, ocular TB, TB pericarditis and breast TB, although any organ can be involved. Diagnosis of EPTB can be baffling, compelling a high index of suspicion owing to paucibacillary load in the biological specimens. A negative smear for acid-fast bacilli, lack of granulomas on histopathology and failure to culture Mycobacterium tuberculosis do not exclude the diagnosis of EPTB. Novel diagnostic modalities such as nucleic acid amplification (NAA) can be useful in varied forms of EPTB. This review is primarily focused on the diagnosis of several clinical forms of EPTB by polymerase chain reaction (PCR) using different gene targets.

Tuberculous meningitis: diagnosis and treatment overview

Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis (TB) and has very high morbidity and mortality. TBM is typically a subacute disease with symptoms that may persist for weeks before diagnosis. Characteristic cerebrospinal fluid (CSF) findings of TBM include a lymphocytic-predominant pleiocytosis, elevated protein, and low glucose. CSF acid-fast smear and culture have relatively low sensitivity but yield is increased with multiple, large volume samples. Nucleic acid amplification of the CSF by PCR is highly specific but suboptimal sensitivity precludes ruling out TBM with a negative test. Treatment for TBM should be initiated as soon as clinical suspicion is supported by initial CSF studies. Empiric treatment should include at least four first-line drugs, preferably isoniazid, rifampin, pyrazinamide, and streptomycin or ethambutol; the role of fluoroquinolones remains to be determined. Adjunctive treatment with corticosteroids has been shown to improve mortality with TBM. In HIV-positive individuals with TBM, important treatment considerations include drug interactions, development of immune reconstitution inflammatory syndrome, unclear benefit of adjunctive corticosteroids, and higher rates of drug-resistant TB. Testing the efficacy of second-line and new anti-TB drugs in animal models of experimental TBM is needed to help determine the optimal regimen for drug-resistant TB.