Rapid and simple detection of a mycobacterium circulating antigen in serum of pulmonary tuberculosis patients by using a monoclonal antibody and Fast-Dot-ELISA

Recognition of specific immunogenic antigens with potential diagnostic value in multi-drug resistant Mycobacterium tuberculosis inducing humoral immunity in MDR-TB patients

Tuberculosis (TB) as a public health crisis is caused by the intracellular bacterium Mycobacterium tuberculosis. Detection of immunogenic proteins in TB is valuable for the development of diagnostic tests, vaccine formulations and monitoring treatment outcome. In this study, we differentiated the immune-reactivity of proteins in multidrug-resistant tuberculosis (MDRTB) and drug-susceptible strains using purified anti-MDRTB antibodies isolated from inpatients. Our data showed that the anti- MDRTB antibody was well able to detect the MDR strain in the patient's sputum. The immunogenic proteins of MDRTB were purified by affinity chromatography and subjected to matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Analysis of the data revealed that seven MDRTB immunogenic proteins, including Rv2986c (HupB), Rv3699, Rv1133c (MetE), Rv0440 (GroEL), Rv3057c, Rv2558 and Rv2971 are involved in DNA stability, metabolism, cellular processes and some unknown functions. Similarities in the electrophoresis protein profiles were evident between the extracts of MDR and sensitive TB strains. However, the protein expression patterns of MDRTB isolates were distinguishable from that formed by susceptible TB strains.

Comparing mRNA expression and protein abundance in MDR Mycobacterium tuberculosis: Novel protein candidates, Rv0443, Rv0379 and Rv0147 as TB potential diagnostic or therapeutic targets

Tuberculosis (TB) is a sizable public health threat in the world. This study was conducted to determine the differential protein composition between susceptible and MDRTB strains. Tuberculosis proteins were extracted by Triton™ X-114 and ammonium sulfate. Two-dimensional gel electrophoresis protein spots were selected for identification by mass spectrometry and mRNA expression levels were measured by real- time PCR. 2DE-Western blot and T cell epitope prediction for identified proteins were made by the IEDB server. The result shows at least six protein spots (Rv0147, Rv3597c, Rv0379, Rv3699, Rv1392 and Rv0443) were differentially expressed in MDRTB isolates. However, difference in mRNA gene expression was not found in the six mRNA genes. 2DE-Western blot procedures indicated strong reaction against MDRTB proteins corresponds to 13, 16 and 55 kDa areas that might be used as new diagnostic tools. In conclusion, these MDRTB proteins identified in this study could be reliable TB diagnostic candidates or therapeutic targets.

Simultaneous determination of ochratoxin A and enterotoxin A in milk by magnetic nanoparticles based fluorescent immunoassay

Ochratoxin A (OTA) and staphylococcus enterotoxin A (SEA) are highly toxic contaminants and have induced human health problems. They commonly occur in milk and milk products. A competitive fluorescent immunoassay was developed for rapid and simultaneous determination of these toxins in milk samples. The procedure was based on the competitive immunoreactions between antigens in sample and antigen-fluorescent dye conjugates with immobilised antibodies on magnetic nanoparticles (MNPs). Each monoclonal antibody specifically recognises its corresponding toxin (antigen), and there is no cross-reactivity in the assay. First, monoclonal antibodies against OTA and SEA were produced. The activity of the obtained antibodies was determined by fluorescent-linked immunosorbent assay. Then, the monoclonal antibodies were immobilised on MNPs. The amounts of immobilised anti-OTA antibody and anti-SEA antibody were determined to be 20 and 22 μg mL^-1, respectively. The antigen-fluorescent dye conjugates OTA-OVA-ATTO620 and SEA-FITC were prepared. The optimal amount of immobilised antibodies for competitive immunoassay was determined. It was found that the linear range of OTA in buffer was larger (0.001-100 ng mL^-1) than the linear range of SEA (0.001-20 ng mL^-1). The results for simultaneous determination of OTA and SEA in sixfold diluted milk were almost the same in buffer; the linear range for OTA was from 0.005  to 100 ng mL^-1 and for SEA from 0.005  to 20 ng mL^-1. The detection limit for both OTA and SEA in milk was 0.004 ng mL^-1. The developed method took half the time of the individual assays (20 min). The assay was evaluated using spiked milk samples. The influences of somatic cell count, fat, pH and protein concentration in milk on immunoassay were studied. In summary, this developed immunoassay could provide an effective and rapid approach for detecting multi-toxins in milk samples.

Evaluation of the Dot-ELISA as a diagnostic test for human strongyloidiasis based on the detection of IgA in saliva

This study aimed to evaluate the use of saliva samples in the Dot-ELISA test for immunodiagnosis of human strongyloidiasis. The Dot-ELISA presented similar results to the ELISA test, with 70% and 60% sensitivity and 85% and 90% specificity, respectively, for IgA in the saliva. The Dot-ELISA with alternative saliva samples may be a suitable tool for diagnosing human strongyloidiasis, especially in populations with high levels of exposure to helminth.

Immunofluorescence Assay Using Monoclonal and Polyclonal Antibodies for Detection of Staphylococcal Enterotoxins A in Milk

Objectives:

Staphylococcus aureus is a Gram-positive microorganism. S. aureus can grow in various foods and cause food poisoning by secreting enterotoxins. The most common enterotoxins involved in food poisoning are staphylococcal enterotoxin A and staphylococcal enterotoxin B, but Staphylococcal Enterotoxin A (SEA) is predominant. The main types of food contaminated with SEs are meat and meat products, poultry and eggs, milk and dairy products. The aim of this study was to develop a rapid and sensitive fluorescence immunoassay for detection of staphylococcal enterotoxin A in milk.

Methods:

Monoclonal and polyclonal antibodies for SEA were produced and characterized. Competitive fluorescence immunoassay based on Magnetic Nanoparticles (MNPs) was performed and optimized. MNPs were used as a solid carrier of the antibodies. The first step of the assay was immunoreaction between the immobilized antibody onto MNPs and SEA in milk sample. Then the fluorescein-SEA conjugate was added to the sample. Thus, competitive immunoreaction between MNP-mAb/MNP-pAb with SEA and SEA-FITC was performed. These immuno-complexes were separated by a magnetic separator and the obtained supernatants were analyzed. The fluorescent signal from the excess of conjugated SEA was proportional to the SEA contained in the milk. The assay duration was only 30 min.

Results:

The fluorescence immunoassays performed with polyclonal antibody had linear ranges from 5 pg/mL to 100 ng/mL SEA in a buffer, and from 50 pg/mL to 50 ng/mL SEA in spiked milk samples. While the same assays performed with monoclonal antibody had linear ranges from 1 pg/mL to 20 ng/mL SEA in buffer, and from 10 pg/mL to 10 ng/mL SEA in spiked milk samples. The detection limits of the developed immunoassays performed in milk were: 48 pg/mL with polyclonal antibody and 9 pg/mL with monoclonal antibody.

Conclusion:

A rapid and sensitive fluorescence immunoassay based on magnetic nanoparticles with a polyclonal and monoclonal antibody for determination of staphylococcal enterotoxin A in milk was developed.

Development, optimization, and validation of an in-house Dot-ELISA rapid test based on SAG1 and GRA7 proteins for serological detection of Toxoplasma gondii infections

Background

The aim of the present study was to develop a simple, portable, and rapid assay for serodiagnosis of toxoplasmosis based on recombinant Toxoplasma gondii (T. gondii) SAG1 (rSAG1) and GRA7 (rGRA7) proteins.

Methods

The rSAG1 and rGRA7 proteins were expressed in Escherichia coli (E. coli) and purified in a single step by immobilized metal ion affinity chromatography. The immunoreactivity of the recombinant antigens was tested in an in-house IgG and IgM Dot enzyme-linked immunosorbent assay (Dot-ELISA) for potential use in serodiagnosis of T. gondii infection.

Results

Results from the comparison of in-house rSAG1-Dot-ELISA with ELISA for the detection of anti-Toxoplasma IgG and IgM include sensitivity of 83.7% and 81.2%, specificity of 90.2% and 89.3%, positive predictive values of 85.9% and 68.4%, and negative predictive values of 88.6% and 94.3%, respectively. Sensitivity of 66.2%, specificity of 81.2%, positive predictive values of 71.6%, and negative predictive values of 77.1% were concluded from in-house IgG rGRA7-Dot-ELISA. The sensitivity and specificity of IgM rGRA7-Dot-ELISA included 87.5% and 83.9%, respectively. Sensitivity and specificity of in-house Dot-ELISA for a combination of rSAG1 and rGRA7 included 87.5% and 91.1% for IgG and IgM, respectively. Sensitivity and specificity of a combination of rSAG1 and rGRA7 for the detection of IgM in suspected sera to acute toxoplasmosis were higher than those for the detection of IgG in sera with chronic infections (90.6% and 92% instead of 86.2% and 91.6%, respectively).

Conclusion

The highlighted parameters of combined recombinant proteins were more significant than those of single recombinant proteins in in-house Dot-ELISA. These data suggest that the in-house Dot-ELISA based on rSAG1 and rGRA7 combination is a promising diagnostic tool with a similar sensitivity to the native antigens of T. gondii, which can be used for the serodiagnosis of toxoplasmosis in fields as well as less equipped laboratories.

Cellular immune response in MDR-TB patients to different protein expression of MDR and susceptible Mycobacterium tuberculosis: Rv0147, a novel MDR-TB biomarker

Tuberculosis (TB) is a crucial public health problem with prevalence of multidrug resistant (MDR) rising. An accurate TB biomarker is urgently needed to monitor the response to treatment in patients with MDR tuberculosis. To analyze interaction between selected MDR-TB purified protein and immune cells, dendritic cells from MDR-TB patients and healthy subjects were stimulated by 55KDa protein fractions (Rv0147). The purified proteins identified by proteomic techniques (two-dimensional gel electrophoresis, mass spectrometry) and peptide sequences are known to bind a MHC class I alleles which are extracted from the Immune Epitope Database and Analysis Resource database ( www.iedb.org ). T cells were isolated from PBMC by negative selection and cells were cultured in RPMI-1640 at 37 °C and 5% CO₂. Cell culture was assayed for cytokine IL-10 and INF-γ by ELISA. We found that INF-γ production was significantly (335 ± 35.5 pg/ml, P ˂ 0.05) upregulated after protein candidate (Rv0147) stimulation by dendritic cells from MDR-TB patients, whereas IL-10 production was greatly reduced compared with production in healthy subjects (212 ± 9.94 pg/ml, P ˂ 0.05). In fact, the purified protein, Rv0147, stimulated dendritic cells from MDR-TB patients, failed to produce IL-10 and directly stimulates INF-γ production by T cells. These results suggest that the purified protein, Rv0147, may stimulate Th1 type protective cytokine response in MDR-TB patients but not in normal subjects. The production of INF-γ but not IL-10 in the presence of purified protein, Rv0147, may be shifted to Th1 responses in MDR-TB patients and supports its potential as protein vaccine candidates against TB.

Sera from patients with active pulmonary tuberculosis and their household contacts induce nuclear changes in neutrophils

Background

Resident alveolar macrophages, dendritic cells, and immigrating neutrophils (NEU) are the first cells to contact Mycobacterium tuberculosis in the lung. These cells, and additional lymphoid cells in the developing granuloma, release a series of components that may concentrate in the serum and affect disease progression.

Purpose

The aim of this study was to investigate the effect of the serum from tuberculosis (TB) patients and their household contacts (HHC) on the nuclear morphology of NEU.

Materials and methods

NEU from healthy (HLT) people were incubated with sera from patients with active pulmonary TB, their HHC, and unrelated people. Changes in the nuclear morphology of NEU were analyzed by light and electron microscopy.

Results

Sera from patients with TB induced changes in the nuclear morphology of NEU that included pyknosis, swelling, apoptosis, and netosis in some cases. Sera from some HHC induced similar changes, while sera from HLT people had no significant effects. Bacteria did not appear to participate in this phenomenon because bacteremia is not a recognized feature of nonmiliary TB, and because sera from patients that induced nuclear changes maintained their effect after filtration through 0.22 µm membranes. Neither anti-mycobacterial antibodies, TNFα, IL-6, IFNγ, or IL-8 participated in the phenomenon. In contrast, soluble mycobacterial antigens were likely candidates, as small quantities of soluble M. tuberculosis antigens added to the sera of HLT people led to the induction of nuclear changes in NEU in a dose-dependent manner.

Conclusion

These results might help to detect subclinical TB within HHC, thus leading to a recommendation of prophylactic treatment.

Aptamer based voltammetric biosensor for Mycobacterium tuberculosis antigen ESAT-6 using a nanohybrid material composed of reduced graphene oxide and a metal-organic framework

The 6-kDa early secretory antigenic target referred to as ESAT-6 is a virulence factor secreted by Mycobacterium tuberculosis (MTB). This work describes a voltammetric aptasensor for ultrasensitive detection of ESAT-6. Reduced graphene oxide doped with metal-organic framework (MOF-rGO) was deposited on a glassy carbon electrode (GCE). This increases the immobilization of electroactive Toluidine Blue (TB) and facilitates the electron transfer from TB to the modified GCE. Platinum/gold core/shell (Pt@Au) nanoparticles were used to assemble thiolated ESAT-6 binding aptamer (EBA) on a modified electrode and to further amplify the response to TB. The modified GCE, typically operated at -0.36 V (vs. SCE), has a linear response in 1.0 × 10^-4 to 2.0 × 10² ng⋅mL^-1 ESAT-6 concentration range, and the limit of detection (LOD) for ESAT-6 is as low as 3.3 × 10^-5 ng⋅mL^-1. It exhibits satisfactory specificity and reproducibility when analyzing spiked human serum. Graphical abstract Schematic presentation of a voltammetric aptasensor for Mycobacterium tuberculosis antigen ESAT-6 using a glassy carbon electrode modified with reduced graphene oxide (rGO) and a metal-organic framework (MOF). The limit of detection for ESAT-6 is as low as 3.3 × 10^-5 ng/mL.

Mycothiol acetyltransferase (Rv0819) of Mycobacterium tuberculosis is a potential biomarker for direct diagnosis of tuberculosis using patient serum specimens

Mycobacterium tuberculosis infection constitutes a global threat that results in significant morbidity and mortality worldwide. Efficient and early diagnosis of tuberculosis (TB) is of paramount importance for successful treatment. The aim of the current study is to investigate the mycobacterial mycothiol acetyltransferase Rv0819 as a potential novel biomarker for the diagnosis of active TB infection. The gene encoding Rv0819 was cloned and successfully expressed in Escherichia coli. The recombinant Rv0819 was purified using metal affinity chromatography and was used to raise murine polyclonal antibodies against Rv0819. The raised antibodies were employed for direct detection of Rv0819 in patient serum samples using dot blot assay and competitive enzyme-linked immunosorbent assay (ELISA). Serum samples were obtained from 68 confirmed new TB patients and 35 healthy volunteers as negative controls. The dot blot assay showed sensitivity of 64·7% and specificity of 100%, whereas the competitive ELISA assay showed lower sensitivity (54·4%) and specificity (88·57%). The overall sensitivity of the combined results of the two tests was found to be 89·7%. Overall, the mycobacterial Rv0819 is a potential TB serum biomarker that can be exploited, in combination with other TB biomarkers, for efficient and reliable diagnosis of active TB infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

The early and accurate diagnosis of tuberculosis infection is of paramount importance for initiating treatment and avoiding clinical complications. Most current diagnostic tests have poor sensitivity and/or specificity and in many cases they are too expensive for routine diagnostic testing in resource-limited settings. In the current study, we examined a novel mycobacterial serum biomarker, namely mycothiol acetyltransferase Rv0819. The antigen was detectable in serum specimens of a significant number of tuberculosis patients. This article proves the importance of Rv0819 and paves the way towards its future use as a useful diagnostic marker for tuberculosis infection.

Fullerene-doped polyaniline as new redox nanoprobe and catalyst in electrochemical aptasensor for ultrasensitive detection of Mycobacterium tuberculosis MPT64 antigen in human serum

Tuberculosis caused by Mycobacterium tuberculosis (MTB) is still a major threat to global public health. However, the existing methods for MTB detection are usually complicated and time consuming with unsatisfactory sensitivity and specificity. In this work, a relatively simple and ultrasensitive electrochemical aptasensor based on novel signal generation and amplification was constructed for the determination of MTB antigen MPT64. The coil-like fullerene (C₆₀)-doped polyaniline (C₆₀-PAn) nanohybrids with large surface area, abundant active groups and excellent electric performance were synthesized and used both as new redox nanoprobe and catalyst for the generation and amplification of electrochemical signal for the first time. Then gold nanoparticles decorated C₆₀-PAn nanocomposites (GNPs-C₆₀-PAn) were labeled with signal aptamer to form the tracer label. After the sandwich reaction of target MPT64 antigen between capture aptamer and the tracer label, a distinguishing detection signal of C₆₀-PAn would be observed. Moreover, the detection signal could be enormously enhanced towards the efficient electrocatalytic oxidation of ascorbic acid based on C₆₀-PAn, resulting in further improvement of the sensitivity. With the excellent redox and electrocatalytic activity of C₆₀-PAn, a wide detection linear range from 0.02 to 1000 pg/mL was obtained with a detection limit of 20 fg/mL for MPT64. The proposed aptasensor showed high selectivity to target antigen compared with possible interfering substances. More importantly, it also exhibited excellent specificity and sensitivity for MPT64 detection in serum samples of tuberculosis patients, which provided a rapid and efficient detection method for MTB infection.

Optimization of polyvinylidene fluoride (PVDF) membrane fabrication for protein binding using statistical experimental design

Statistical experimental design was employed to optimize the preparation conditions of polyvinylidenefluoride (PVDF) membranes. Three variables considered were polymer concentration, dissolving temperature, and casting thickness, whereby the response variable was membrane-protein binding. The optimum preparation for the PVDF membrane was a polymer concentration of 16.55 wt%, a dissolving temperature of 27.5°C, and a casting thickness of 450 µm. The statistical model exhibits a deviation between the predicted and actual responses of less than 5%. Further characterization of the formed PVDF membrane showed that the morphology of the membrane was in line with the membrane-protein binding performance.

MDR-TB Antibody Response (Western Blot) to Fractions of Isoniazid and Rifampicin Resistant Antigens of Mycobacterium tuberculosis

Drug-resistant TB poses a major threat to control of TB worldwide. Despite progress in the detection of Multidrug-resistant TB (MDR-TB) cases, a major diagnostic gap remains: 55% of reported TB patients estimated to have MDR-TB were not detected in 2013. MDR-TB antigens were conjugated to CNBr-activated Sepharose 4B. Specific polyclonal antibodies against MDR-TB Ags were prepared in rabbits using two boosted injections of the MDR-TB antigen. The antibodies were purified and treated with susceptible TB to remove any non-specific and cross-reactive antibodies. In the present study, comparative analysis of electrophoretic pattern of different antigens of INH/RIF-resistant TB were studied for identifying protein profiles. A RIF-resistant TB antigen was shown here to have different protein profiles from INH-resistant TB isolate. The results of Western blotting analysis showed that in the RIF- and INH-resistant antigenic fractions some bands of 14.4 and 45 kDa as immunogenic were common. Moreover, four bands of RIF-resistant TB antigen fractions (16, 19, 21, and 45 KDa) and one band of INH-resistant TB (about 26 KDa) were detected as diagnostic antigens. This study suggests that the Western blot is an accurate test to survey INH- and RIF-resistant TB antigens of M. tuberculosis infection. These findings indicate that MDR-TB diagnosis (based on Ag detection) could be useful in the identification of disease stages that precede symptomatic and microbiologically positive TB, such as subclinical and incipient TB.

Pathogen-derived biomarkers for active tuberculosis diagnosis

Tuberculosis (TB) is an infectious disease caused by members of Mycobacterium tuberculosis complex. Despite the availability of effective treatments, TB remains a major public health concern in most low and middle-income countries, representing worldwide the second leading cause of death from an infectious disease. Inadequate case detection and failures to classify the disease status hamper proper TB control. The limitations of the conventional diagnostic methods have encouraged much research activities in this field, but there is still an urgent need for an accurate point of care test for active TB diagnosis. A rapid, precise, and inexpensive TB diagnostic test would allow an earlier implementation of an appropriate treatment and the reduction of disease transmission. Pathogen-derived molecules present in clinical specimens of affected patients are being validated for that purpose. This short review aims to summarize the available data regarding biomarkers derived from M. tuberculosis, and their current usage in active TB diagnosis.

Evaluation of antigen detection test (chromatographic immunoassay): potential to replace the antibody assay using purified 45-kDa protein for rapid diagnosis of tuberculosis

BACKGROUND

The current strategy for combating tuberculosis (TB) is based on the early detection and treatment of patients to halt transmission. The present study was conducted to evaluate the diagnostic potential of three Mycobacterium tuberculosis antigens, 45-kDa, A60, and sonicated MTB antigen (SmTB-Ag), as antibody/antigen detection methods for the rapid and accurate diagnosis of TB.

METHODS

The SmTB-Ag and 45-kDa antigens were purified and A60 antigen was supplied by Anda-Biologicals, France. The 45-kDa and A60 antigens (for antibody detection procedures) and SmTB-Ag (for antigen detection test) were tested in the same study subjects. ELISA and immunochromatographic (rapid) test were performed on 201 sputum and serum samples. Ninety-eight samples from TB patients and 103 samples from control individuals were studied.

RESULTS

The mean absorbance value of antibodies against 45-kDa antigen in the TB patients were (1.17 ± 0.44, CI 1.09-1.26), significantly higher than in the non-TB group, (0.8 ± 0.28, CI 0.74-0.85, P < 0.05). The sensitivities of tests using two antigens, 84% for the 45-kDa antigen and 65% for the A60 antigen, were lower than SmTB-Ag(93%). The rapid test yielded 93% sensitivity and 92% specificity.

CONCLUSION

Findings highlighted the importance of antigen detection as a diagnostic tool. The rapid test evaluated in this study may be useful for diagnosis of TB.

An evaluation of the dot-ELISA procedure as a diagnostic test in an area with a high prevalence of human Toxocara canis infection

The aim of this work was to evaluate a dot-enzyme-linked immunosorbent assay (dot-ELISA) using excretory-secretory antigens from the larval stages of Toxocara canis for the diagnosis of toxocariasis. A secondary aim was to establish the optimal conditions for its use in an area with a high prevalence of human T. canis infection. The dot-ELISA test was standardised using different concentrations of the antigen fixed on nitrocellulose paper strips and increasing dilutions of the serum and conjugate. Both the dot-ELISA and standard ELISA methods were tested in parallel with the same batch of sera from controls and from individuals living in the problem area. The best results were obtained with 1.33 µg/mL of antigen, dilutions of 1/80 for the samples and controls and a dilution of 1/5,000 for the anti-human IgG-peroxidase conjugate. All steps of the procedure were performed at room temperature. The coincidence between ELISA and dot-ELISA was 85% and the kappa index was 0.72. The dot-ELISA test described here is rapid, easy to perform and does not require expensive equipment. Thus, this test is suitable for the serological diagnosis of human T. canis infection in field surveys and in the primary health care centres of endemic regions.

Monoclonal antibodies against a Mycobacterium tuberculosis Ag85B-Hsp16.3 fusion protein

The secreted Mycobacterium tuberculosis (MTB) proteins, Ag85B and Hsp16.3, have been the focus of intensive research in recent years. These proteins have high sensitivity in bacterium-negative tuberculosis (TB) patients, and are valuable for the rapid diagnosis of bacterium-negative TB. Fusion proteins including multiple antigens such as Ag85B and Hsp16.3 provide improved sensitivity and specificity for serological diagnosis of active TB compared with a single antigen. Many studies have shown that the production of MAbs recognizing a specific repertoire of M. tuberculosis antigens and the tests based on monoclonal antibodies have been found to be valuable in positive detection of TB, particularly for smear-positive pulmonary TB. A number of MAbs are currently used for serodiagnosis of TB. Therefore, an Ag85B-Hsp16.3 fusion protein was expressed and purified using an E. coli system in this study. Three Ag85B-Hsp16.3 fusion protein-specific MAbs were generated by routine murine hybridoma techniques. The titer, specificity, and relative affinity of all three MAbs were determined by ELISA and the serological responses were analyzed. The levels of antigens in a proportion of TB patients were shown to be significantly higher than those in healthy controls. The sensitivity and specificity of the currently available detection systems is likely to be improved by the employment of a combination of these MAbs with others that are already in use.

A highly efficient Ziehl-Neelsen stain: identifying de novo intracellular Mycobacterium tuberculosis and improving detection of extracellular M. tuberculosis in cerebrospinal fluid

Tuberculous meningitis leads to a devastating outcome, and early diagnosis and rapid chemotherapy are vital to reduce morbidity and mortality. Since Mycobacterium tuberculosis is a kind of cytozoic pathogen and its numbers are very few in cerebrospinal fluid, detecting M. tuberculosis in cerebrospinal fluid from tuberculous meningitis patients is still a challenge for clinicians. Ziehl-Neelsen stain, the current feasible microbiological method for the diagnosis of tuberculosis, often needs a large amount of cerebrospinal fluid specimen but shows a low detection rate of M. tuberculosis. Here, we developed a modified Ziehl-Neelsen stain, involving cytospin slides with Triton processing, in which only 0.5 ml of cerebrospinal fluid specimens was required. This method not only improved the detection rate of extracellular M. tuberculosis significantly but also identified intracellular M. tuberculosis in the neutrophils, monocytes, and lymphocytes clearly. Thus, our modified method is more effective and sensitive than the conventional Ziehl-Neelsen stain, providing clinicians a convenient yet powerful tool for rapidly diagnosing tuberculous meningitis.

Systematic review and meta-analysis of antigen detection tests for the diagnosis of tuberculosis

Tests that detect Mycobacterium tuberculosis antigens in clinical specimens could provide rapid direct evidence of active disease. We performed a systematic review to assess the diagnostic accuracy of antigen detection tests for active tuberculosis (TB) according to standard methods and summarized test performance using bivariate random effects meta-analysis. Overall, study quality was a concern. For pulmonary TB (47 studies, 5,036 participants), sensitivity estimates ranged from 2% to 100% and specificity from 33% to 100%. Lipoarabinomannan (LAM) was the antigen most frequently targeted (23 studies, 49%). The pooled sensitivity of urine LAM was higher in HIV-infected than HIV-uninfected individuals (47%; 95% confidence interval [CI], 26 to 68% versus 14%; 95% CI, 4 to 38%); pooled specificity estimates were similar: 96%; 95% CI, 81 to 100% and 97%; 95% CI, 86 to 100%, respectively. For extrapulmonary TB (21 studies, 1,616 participants), sensitivity estimates ranged from 0% to 100% and specificity estimates from 62% to 100%. Five studies targeting LAM, ESAT-6, Ag85 complex, and the 65-kDa antigen in cerebrospinal fluid, when pooled, yielded the highest sensitivity (87%; 95% CI, 61 to 98%), but low specificity (84%; 95% CI, 60 to 95%). Because of the limited number of studies targeting any specific antigen other than LAM, we could not draw firm conclusions about the overall clinical usefulness of these tests. Further studies are warranted to determine the value of LAM detection for TB meningitis in high-HIV-prevalence settings. Considering that antigen detection tests could be translated into rapid point-of-care tests, research to improve their performance is urgently needed.

Biomarkers of disease activity, cure, and relapse in tuberculosis

The changing face of tuberculosis, with epidemics fueled by HIV and urbanization in much of the world and a relative increase in the importance of latent tuberculosis as a source of cases in the more economically developed countries, has led to a demand for more robust, clinically applicable diagnostic tools. As a result, research aiming to identify biomarkers of Mycobacterium tuberculosis infection and disease has flourished. This article discusses the most recent findings of that work.