Evaluation of an in-house-developed PCR for the diagnosis of tuberculous meningitis in Indian children

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.

Comparative evaluation of IS6110 and protein antigen b PCR in cerebrospinal fluid for rapid diagnosis of tuberculous meningitis in children

Introduction. Childhood tuberculosis meningitis is a severe form of tuberculosis with high morbidity and mortality. The diagnosis is frequently missed and delayed due to lack of sensitive tests like acid-fast bacilli (AFB) smear and delayed results by culture.Aims. To compare the role of IS6110 and protein antigen b PCR in cerebrospinal fluid (CSF) for rapid diagnosis of tuberculous meningitis (TBM) in children.Methodology. Forty-five cases of TBM and 20 controls were enrolled in this prospective study.Results. The mean ages of cases and controls were 4.2±0.5 years and 4.5±0.7 years, respectively. In the TBM group, two-thirds of the children were <4 years of age, and 62 % were males. Sensitivities of AFB smear examination, Löwenstein-Jensen (LJ) medium and bactenecin (BACTEC) culture in cases were 4.4, 0 and 2.2%, respectively. The protein antigen b PCR was most sensitive as it was positive in 35 (77.8 %) of TBM patients; IS6110 PCR was positive in 27 (60 %) patients. Both PCR-based tests had higher positivity than conventional tests and BACTEC culture. No significant difference was seen between the PCR tests. Excellent agreement was observed between both PCR-based tests as they were concordant for 26 positive samples and 35 negative samples.Conclusion. Protein b PCR is a sensitive and rapid method for the diagnosis of TBM (sensitivity 77.8 %). Both PCRs were more sensitive than smear, LJ and BACTEC. The specificity of both PCR was 100 %.

Challenging diagnosis of gastrointestinal tuberculosis made simpler with multi-targeted loop-mediated isothermal amplification assay

BACKGROUND

Prompt and accurate diagnosis of gastrointestinal tuberculosis (GITB) is highly challenging. Current conventional techniques lack sensitivity and are time-consuming. Multi targeted loop-mediated isothermal amplification (LAMP) using two targets (IS6110 and MPB64) is a promising technique for rapid diagnosis of TB.

METHODS

LAMP test using IS6110 and MPB64 targets for M. tuberculosis complex was performed on ileocecal biopsy samples of 35 clinically suspected patients of GITB and 30 ileocecal biopsy samples of non-tuberculosis control subjects. Results of IS6110 LAMP and MPB64 LAMP were compared with IS6110 PCR and culture INFERENCE: Overall LAMP test (using any of the two targets) had a sensitivity and specificity of 100 and 100%, respectively, for confirmed GITB (five culture positive) cases and 85.71 and 100%, respectively, for clinically suspected 30 ileocecal biopsy samples of GITB. Sensitivity of IS6110 LAMP, MPB64 LAMP and IS6110 PCR for clinically suspected cases was 22 (73.33%), 24 (80%) and 21 (70%), respectively. In total 35 GITB patients, the overall sensitivity of microscopy, culture, IS6110 PCR, IS6110 LAMP, MPB64 LAMP and the multi-targeted LAMP assay (if any of the two targets were used) were 5.71, 14.28, 68.57, 74.28, 82.85 and 85.71%, respectively. Specificity of all the tests was 100%. There were three cases which were missed by IS6110 LAMP and two cases by MPB64 LAMP.

CONCLUSION

Multi-targeted LAMP is a promising technique for rapid and accurate diagnosis of GITB.

Role of multiplex polymerase chain reaction in diagnosing tubercular meningitis

Tuberculous meningitis (TBM) is one of the most serious manifestations of extrapulmonary tuberculosis. Timely and accurate diagnosis provides a favorable prognosis in patients with TBM. The study evaluated the use of multiplex polymerase chain reaction (PCR) in the diagnosis of TBM. A study was conducted on 74 patients clinically suspected with TBM. The cerebrospinal fluid (CSF) specimens were processed for smear microscopy, middle brook 7H9 culture, and multiplex PCR using primers directed against IS6110 gene and 38 kD protein for detection of Mycobacterium tuberculosis. The results were analyzed to assess the role of multiplex PCR in the diagnosis of TBM. A total of 26 (35.1%) patients were diagnosed with TBM. Microscopy was negative in all while culture was positive in two cases only. Comparing with clinical diagnosis and CSF adenosine deaminase levels of ≥10 U/L, multiplex PCR showed sensitivity, specificity, positive predictive value, and negative predictive value of 71.4%, 89.6%, 83.3%, and 81.2%, respectively, in the diagnosis of TBM.

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.

Role of PCR method using IS6110 primer in detecting Mycobacterium tuberculosis among the clinically diagnosed childhood tuberculosis patients at an urban hospital in Dhaka, Bangladesh

OBJECTIVE

Better methods are needed for the accurate detection of child tuberculosis (TB). This study compared different laboratory tests and evaluated IS6110 PCR for the detection of Mycobacterium tuberculosis (MTB) among clinically diagnosed child TB patients.

METHODS

A total of 102 paediatric patients (<15 years old) with clinically diagnosed TB were enrolled in this study. The patients were admitted to the icddr,b hospital in Dhaka between 2003 and 2005. Sputum/gastric lavage samples were collected for smear microscopy, culture (solid/Lowenstein-Jensen medium and liquid/MGIT), and IS6110 PCR testing. The sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of smear microscopy and PCR were compared to the two culture methods.

RESULTS

Three patients were positive on smear microscopy (2.9%). MTB was detected by conventional culture in 15.7% (16/102), liquid culture in 14% (14/100), and IS6110 PCR in 61.8% (63/102). PCR detected an additional 45 patients who were undetected with the three other tests. Compared to conventional and liquid culture, respectively, smear microscopy showed sensitivity of 18.8% and 21.4%, specificity of 100% individually, PPV of 100% individually, and NPV of 86.9% and 88.7%, whereas PCR had sensitivity of 87.5% and 92.9%, specificity of 43% individually, PPV of 22.2% and 21%, and NPV of 94.9% and 97.4%.

CONCLUSIONS

PCR can be useful compared to smear microscopy and culture methods and is applicable as a rapid screening test for child TB. A larger scale study is required to determine its diagnostic efficacy in improving the detection of child TB in the presence and absence of severe malnutrition.

PCR targeting IS6110 in diagnosing tuberculosis in children in comparison to MGIT culture

BACKGROUND

Diagnosis of tuberculosis (TB) in children is difficult in children especially in extrapulmonary tuberculosis (EPTB). This study was conducted to evaluate the use of polymerase chain reaction (PCR) targeting IS6110 in the diagnosis of TB in children with pulmonary TB and EPTB and also to compare its performance with MGIT 960 culture and conventional microscopy.

METHODS

A total of 142 cases (50 pulmonary, 92 extrapulmonary) of suspected TB patients <15 years of age were included in the study. The clinical specimens obtained from these cases were subjected to Ziehl-Neelsen staining (ZN), MGIT 960 TB culture and PCR targeting insertion sequence IS6110. Sensitivity and specificity of PCR were calculated in pulmonary and extrapulmonary specimens. The results were compared to MGIT culture.

RESULTS

PCR targeting IS6110 sequence had sensitivity of 69.01% in various clinical specimens which was significantly more than MGIT culture showing a sensitivity of 47.41% (p<0.05). Sensitivity of PCR IS6110 in extrapulmonary specimens was 65.21% which was lower than sensitivity in pulmonary specimens (76%) but was not statistically significant (p>0.05).

CONCLUSIONS

Diagnostic efficacy of PCR IS6110 in pulmonary and extrapulmonary TB cases was similar. PCR using IS6110 primer had significantly better efficiency than MGIT culture in diagnosing TB in children.

Microbial DNA testing for inflammatory diseases of the brain of uncertain etiology

Neurologists may be confronted with patients who present with inflammatory brain lesions where the diagnosis cannot be made through history and physical examination alone. Molecular testing for bacterial infections, tuberculosis, and fungal infections may aid in the diagnosis. Since the treatments for these disorders are different and delays can result in permanent neurologic disability and death, rapid and accurate diagnoses are critical. This review provides the neurologist with testing options and recommends ways to enhance sensitivity and specificity.

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.

The Diagnostic Utility of Bact/ALERT and Nested PCR in the Diagnosis of Tuberculous Meningitis

OBJECTIVE

The early laboratory diagnosis of Tuberculous Meningitis (TBM) is crucial, to start the antitubercular chemotherapy and to prevent its complications. However, the conventional methods are either less sensitive or time consuming. Hence, the diagnostic potentials of BacT/ALERT and Polymerase Chain Reaction (PCR) was evaluated in this study.

MATERIAL AND METHOD

The study group comprised of 62 cases and 33 controls. The cases were divided according to Ahuja's criteria into the confirmed (two cases), highly probable (19 cases), probable (26 cases) and the possible (15 cases) subgroups. Ziehl Neelsen's (ZN) and Auramine Phenol (AP) staining, Lowenstein Jensen (LJ) medium culture, BacT/ALERT and nested Polymerase Chain Reaction (PCR) which targeted IS6110 were carried out on all the patients.

OBSERVATION AND RESULTS

The sensitivity of the LJ culture was 3.22%. BacT/ALERT showed a sensitivity and a specificity of 25.80% and 100% and those of nested PCR were found to be 40.32% and 96.97% respectively. The mean detection time of growth of the LJ culture was 31.28 days, whereas that of BacT/ALERT was 20.68 days. The contamination rate in the LJ culture and BacT/ALERT were 7.2% and 5.8% respectively.

CONCLUSION

Nested PCR was found to be more sensitive, followed by BacT/ALERT as compared to the LJ culture and smear microscopy. As both false negative and false positive results have been reported for nested PCR, so it should not be used alone as a criterion for initiating or terminating the therapy, but it should be supported by clinical, radiological, cytological and other microbiological findings.

A twenty-year retrospective study of pediatric tuberculosis in two tertiary hospitals in Rome

BACKGROUND

Tuberculosis (TB) is among the top 10 causes of child death worldwide. Nevertheless, childhood disease has been neglected by tuberculosis control programs.

METHODS

This was a retrospective study of patients < 16 years of age diagnosed with active TB in 2 tertiary hospitals in Rome (Italy), between 1990 and 2009.

RESULTS

Two hundred fourteen cases of active tuberculosis were identified (132 definite, 82 probable). Pulmonary involvement was the most common form (75.5%), followed by lymphadenopathy (15.4%) and central nervous system TB (11%). Fever (51.86%) and cough (40%) were the most common presenting symptoms. A total of 23.4% of children were asymptomatic on admission. Sensitivities of the tuberculin skin test and the quantiferon test were 93.4% and 97%, respectively. Both tests performed in 52 children agreed in 49 cases (94%). Sensitivities for culture, Ziehl-Neelsen staining and polymerase chain reaction were 58%, 25% and 66.3%, respectively. The adult source case was identified in 28% of cases. History of contact with a patient with active TB was associated with pulmonary TB (P = 0.0014), whereas negative history of contact was associated with lymph node (P = 0.0064) and central nervous system TB (P = 0.05).

CONCLUSIONS

Our study emphasizes the difficulty in managing children with suspected TB, because the absence of constitutional symptoms cannot exclude TB, and bacteriologic confirmation is the exception. Immunologic diagnosis can be a valuable tool to identify TB-infected children because the quantiferon test showed high sensitivity in all age groups. This is of primary importance because early identification of children with latent tuberculous infection and appropriate chemoprophylaxis represent, to date, the most important tool to reduce the burden of TB.

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.

The PCR-Based Diagnosis of Central Nervous System Tuberculosis: Up to Date

Central nervous system (CNS) tuberculosis, particularly tuberculous meningitis (TBM), is the severest form of Mycobacterium tuberculosis (M.Tb) infection, causing death or severe neurological defects in more than half of those affected, in spite of recent advancements in available anti-tuberculosis treatment. The definitive diagnosis of CNS tuberculosis depends upon the detection of M.Tb bacilli in the cerebrospinal fluid (CSF). At present, the diagnosis of CNS tuberculosis remains a complex issue because the most widely used conventional “gold standard” based on bacteriological detection methods, such as direct smear and culture identification, cannot rapidly detect M.Tb in CSF specimens with sufficient sensitivity in the acute phase of TBM. Recently, instead of the conventional “gold standard”, the various molecular-based methods including nucleic acid amplification (NAA) assay technique, particularly polymerase chain reaction (PCR) assay, has emerged as a promising new method for the diagnosis of CNS tuberculosis because of its rapidity, sensitivity and specificity. In addition, the innovation of nested PCR assay technique is worthy of note given its contribution to improve the diagnosis of CNS tuberculosis. In this review, an overview of recent progress of the NAA methods, mainly highlighting the PCR assay technique, was presented.

Tuberculosis: laboratory diagnosis

Delay in laboratory diagnosis of tuberculosis (TB) is a major obstacle in TB control programs. There is an imperative need for scale-up of peripheral health care laboratories with conventional and molecular technologies for rapid and reliable diagnosis of TB. A cost-effective diagnostic algorithm for rapid diagnosis of TB should be implemented and followed, thereby reducing cost burden on patients.

Brain tuberculomas, tubercular meningitis, and post-tubercular hydrocephalus in children

Central nervous system tuberculosis in children presents commonly as tubercular meningitis, post-tubercular meningitis hydrocephalus, and much more rarely as space-occupying lesions known as tuberculomas. The occurrence of this condition, though previously reported only in the developing world, is now frequently reported in human immunodeficiency virus positive migrants in the western world. The exact pathogenesis of this condition is still incompletely understood, and the mainstay of treatment is chemotherapeutic regimes. Neurosurgical intervention is rarely necessary, and is confined to cases of hydrocephalus after tubercular meningitis and to large tubeculomas with space-occupying effects.

Multiplex PCR for rapid diagnosis of tuberculous meningitis

Rapid and specific diagnosis of tubercular meningitis is of paramount importance to decrease morbidity and mortality. The aim of the study was to evaluate multiplex PCR using protein b, MPB 64, and IS6110 primers directed against M. tuberculosis complex for the diagnosis of tuberculous meningitis (TBM). Multiplex PCR was performed on 18 TBM confirmed cases (culture was positive), 92 clinically suspected TBM cases and 100 non-TBM (control group) patients. Multiplex PCR had a sensitivity of 94.4% for confirmed cases and specificity of 100% for confirmed TBM cases. In 92 clinically diagnosed but unconfirmed TBM cases, multiplex PCR was positive in 84.78% cases. The overall sensitivity of microscopy, culture and multiplex cases were 1.81, 16.73, and 86.63% and specificity was 100, 100, and 100% respectively. Multiplex PCR using protein b, MPB 64, and IS6110 primers has a high sensitivity and specificity in diagnosis of tubercular meningitis.

Diagnostic value of early secreted antigenic target-6 for the diagnosis of tuberculous meningitis patients

BACKGROUND

The early diagnosis of tuberculous meningitis (TBM) is very crucial, since delayed diagnosis can lead to various neurological manifestations. We have previously developed an in-house indirect enzyme-linked immunosorbent assay (ELISA) for TBM diagnosis using the Antigen 85 (Ag 85) complex. It has been suggested that the Ag 85 complex might give false-positive reactions for individuals vaccinated with Bacillus Calmette-Guérin (BCG).

OBJECTIVES

In the present study, we describe a prospective evaluation demonstrating that early secreted antigenic target- 6 (ESAT-6), which is absent in Mycobacterium bovis BCG strains, is in the cerebrospinal fluid (CSF) of TBM patients.

METHODS

We used an indirect ELISA to detect ESAT-6 antigens in the CSF of TBM patients using polyclonal antibodies against ESAT-6.

RESULTS

Using the indirect ELISA method, we demonstrated a sensitivity and specificity of 80% and 94%, respectively, for the diagnosis of TBM.

CONCLUSION

The detection of ESAT-6 in the CSF of TBM patients by indirect ELISA is a promising method and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.

Clinical practice: diagnosis of childhood tuberculosis

Childhood tuberculosis (TB) represents an important part of the disease burden, yet its diagnosis remains challenging. This review summarizes the clinical, radiological, and bacteriological approaches to diagnose TB infection and disease in children. Fever (possibly intermittent or low grade), weight loss or failure to thrive, and a persistent cough for >2 weeks are the most important clinical signs for pulmonary tuberculosis. Extra-pulmonary TB, which might occur in over 40% of the patients, can have in addition some specific clinical symptoms or signs. Chest radiographs provide important information in many patients and advanced imaging can be applied in case of (and should be restricted to) inconclusive diagnosis. The Mantoux test is positive in up to 70% of non-immunocompromised TB patients, whereas HIV co-infection or malnourishment results in a lower reactivity. Evidence of an adult TB index case is clue for diagnosis of childhood TB in low-endemic countries. Bacteriological confirmation remains difficult and is useful for doubtful cases or when drug resistance is suspected.

Efficient diagnosis of tuberculous meningitis by detection of Mycobacterium tuberculosis DNA in cerebrospinal fluid filtrates using PCR

Tuberculous meningitis (TBM) is the most devastating form of meningitis and prompt diagnosis holds the key to its management. Conventional microbiology has limited utility and nucleic acid-based methods have not been widely accepted for various reasons. In view of the paucibacillary nature of cerebrospinal fluid (CSF) and the recent demonstration of free Mycobacterium tuberculosis DNA in clinical specimens, the present study was designed to evaluate the utility of CSF 'filtrates' for the diagnosis of TBM using PCR. One hundred and sixty-seven CSF samples were analysed from patients with 'suspected' TBM (n=81) and a control group including other cases of meningitis or neurological disorders (n=86). CSF 'sediments' and 'filtrates' were analysed individually for M. tuberculosis DNA by quantitative real-time PCR (qRT-PCR) and conventional PCR. Receiver-operating characteristic curves were generated from qRT-PCR data and cut-off values of 84 and 30 were selected for calling a 'filtrate' or 'sediment' sample positive, respectively. Based on these, TBM was diagnosed with 87.6% and 53.1% sensitivity (P<0.001) in 'filtrates' and 'sediments', respectively, and with 92% specificity each. Conventional devR and IS6110 PCR were also significantly more sensitive in 'filtrates' versus 'sediments' (sensitivity of 87.6% and 85.2% vs 31% and 39.5%, respectively; P<0.001). The qRT-PCR test yielded a positive likelihood ratio of 11 and 6.6 by analysing 'filtrate' and 'sediment' fractions, respectively, which establishes the superiority of the 'filtrate'-based assay over the 'sediment' assay. PCR findings were separately verified in 10 confirmed cases of TBM, where M. tuberculosis DNA was detected using devR PCR assays in 'sediment' and 'filtrate' fractions of all samples. From this study, we conclude that (i) CSF 'filtrates' contain a substantial amount of M. tuberculosis DNA and (ii) 'filtrates' and not 'sediments' are likely to reliably provide a PCR-based diagnosis in 'suspected' TBM patients.

Newer methods over the conventional diagnostic tests for tuberculous meningitis: do they really help?

Rapid diagnosis of tuberculous meningitis (TBM) is crucial as the disease outcome depends on the stage at which the treatment is initiated. The reliability of the available tests has not been established; thus, the present study was conducted to evaluate the conventional diagnostic tests as compared to the newer methods. Cerebrospinal fluid was collected from 100 children, and analyzed for various biochemical and cytological tests. The samples were subjected to Ziehl-Neelsen (Z-N) staining, Lowenstein-Jensen (L-J) culture, BACTEC culture and polymerase chain reaction (PCR). Twenty-two patients could be identified as definitive TBM based on the demonstration of Mycobacterium tuberculosis by BACTEC culture and PCR. Of these 22 cases, Z-N staining was positive in only two and L-J culture in six cases. Both the BACTEC culture and PCR had 100% agreement in the diagnosis of TBM. However, BACTEC culture could be a better diagnostic test as drug sensitivity can also be performed by this method.

Central nervous system tuberculosis: pathogenesis and clinical aspects

Tuberculosis of the central nervous system (CNS) is a highly devastating form of tuberculosis, which, even in the setting of appropriate antitubercular therapy, leads to unacceptable levels of morbidity and mortality. Despite the development of promising molecular diagnostic techniques, diagnosis of CNS tuberculosis relies largely on microbiological methods that are insensitive, and as such, CNS tuberculosis remains a formidable diagnostic challenge. Insights into the basic neuropathogenesis of Mycobacterium tuberculosis and the development of an appropriate animal model are desperately needed. The optimal regimen and length of treatment are largely unknown, and with the rising incidence of multidrug-resistant strains of M. tuberculosis, the development of well-tolerated and effective antibiotics remains a continued need. While the most widely used vaccine in the world largely targets this manifestation of tuberculosis, the BCG vaccine has not fulfilled the promise of eliminating CNS tuberculosis. We put forth this review to highlight the current understanding of the neuropathogenesis of M. tuberculosis, to discuss certain epidemiological, clinical, diagnostic, and therapeutic aspects of CNS tuberculosis, and also to underscore the many unmet needs in this important field.

Improved diagnosis of central nervous system tuberculosis by MPB64-Target PCR

Central nervous system (CNS) tuberculosis is a serious clinical problem, the treatment of which is sometimes hampered by delayed diagnosis. Clearly, prompt laboratory diagnosis is of vital importance as the spectrum of disease is wide and abnormalities of the cerebrospinal fluid (CSF) are incredibly variable. Since delayed hypersensitivity is the underlying immune response, bacterial load is very low. The conventional bacteriological methods rarely detect Mycobacterium tuberculosis in CSF and are of limited use in diagnosis of tuberculous meningitis (TBM). This double blind study was, therefore, directed to the molecular analysis of CNS tuberculosis by an in-house-developed PCR targeted for amplification of a 240bp nucleotide sequence coding for MPB64 protein specific for Mycobacterium tuberculosis. Based on the clinical criteria, 47 patients with CNS tuberculosis and a control group of 10 patients having non-tubercular lesions of the CNS were included in the study. Analyses were done in three groups; one group consisting of 27 patients of TBM, a second group of 20 patients with intracranial tuberculomas and a third group of 10 patients having nontubercular lesions of the CNS acted as control. There were no false positive results by PCR and the specificity worked out to be 100%. In the three study groups, routine CSF analysis (cells and chemistry), CSF for AFB smear and culture were negative in all cases. PCR was positive for 21/27 patients (77.7% sensitivity) of the first group of TBM patients, 6/20 patients (30% sensitivity) of the second group with intracranial tuberculomas were positive by PCR and none was PCR-positive (100% specificity) in the third group. Thus, PCR was found to be more sensitive than any other conventional method in the diagnosis of clinically suspected tubercular meningitis.

Evaluation of the IS6110 PCR assay for the rapid diagnosis of tuberculous meningitis

Background

Tuberculous meningitis (TBM) is one of the common clinical manifestations of extra-pulmonary tuberculosis. It is difficult to diagnose due to a lack of rapid, sensitive, and specific tests. Newer methods, which are easy and reliable, are required to diagnose TBM at an early stage. Thus our aim was to evaluate the polymerase chain reaction (PCR) technique, using primers directed against the IS6110 gene, for the detection of Mycobacterium tuberculosis in the CSF, for the diagnosis of TBM patients.

Methods

An in-house IS6110 PCR method using a specific pair of primers designed to amplify the insertion sequence, IS6110, in the M. tuberculosis genome was used to analyze CSF. A total of 80 CSF samples from different groups of patients were studied (confirmed TBM n = 35, clinically suspected TBM n = 16, non-TBM infectious meningitis n = 12, non infectious neurological diseases n = 17).

Results

PCR gave a sensitivity of 91.4% and specificity of 75.9% for the diagnosis of TBM in patients with TBM confirmed by culture. In 16 clinically diagnosed, but unconfirmed, TBM cases PCR was positive in 10 (62.5%) cases. There were seven (24.1%) PCR-positive cases among the 29 patients with non-TBM and non-infectious neurological disease.

Conclusion

We conclude that the performance of an in-house IS6110 PCR assay is valuable in the rapid diagnosis of tuberculous meningitis.

Utility of the polymerase chain reaction in the diagnosis of tuberculous meningitis

Due to inconsistent clinical presentations and the lack of a rapid, sensitive and specific test, tuberculous meningitis (TBM) is particularly difficult to diagnose. The present study was carried out to determine the utility of the polymerase chain reaction (PCR) using INS primers in the diagnosis of TBM and to compare the efficacy of two different DNA extraction protocols. Fifty-seven cerebrospinal fluid (CSF) samples from suspected cases of meningitis -- 30 definitive/possible TBM and 27 non-TBM -- were processed for microscopy, culture and PCR. Results of computer tomographic (CT) scan findings were noted. The results of smear, culture and PCR were compared using culture and/or clinical response to treatment as the gold standard. The sensitivity of microscopy, culture, CT scan and PCR was 3.3%, 26.7%, 60.0% and 66.7%, respectively. PCR following QIAmp DNA extraction had a sensitivity of 66.7% compared to PCR following a DNA extraction protocol based on the use of cetyl trimethyl ammonium bromide (CTAB) (50%). PCR was positive in all culture-positive CSF samples using either extraction method. PCR is a rapid and sensitive technique; above all, it can diagnose tuberculous meningitis at a very early stage.

Occurrence of overlooked zoonotic tuberculosis: detection of Mycobacterium bovis in human cerebrospinal fluid

The paucibacillary nature of the cerebrospinal fluid (CSF) has been a major obstacle in the diagnosis of human tuberculous meningitis (TBM). This study shows that with molecular techniques direct precise determination to the species level of mycobacterial pathogens can be made. The present report describes the utility of a nested PCR (N-PCR) assay (A. Mishra, A. Singhal, D. S. Chauhan, V. M. Katoch, K. Srivastava, S. S. Thakral, S. S. Bharadwaj, V. Sreenivas, and H. K. Prasad, J. Clin. Microbiol. 43:5670-5678, 2005) in detecting M. tuberculosis and M. bovis in human CSF. In 2.8% (6/212) of the samples, M. tuberculosis was detected, and in 17% (36/212), M. bovis was detected. Mixed infection was observed in 22 samples. Comparative analysis of clinical diagnosis, smear microscopy, and N-PCR in 69 patients (TBM, 25; non-TBM, 44) showed that the sensitivity of N-PCR (61.5%) was greater than that of smear microscopy (38.4%). Determination to the species level is important from the viewpoint of determining the prevalence of these mycobacteria in a community and would influence strategies currently adopted for the prevention of tuberculosis.