MPT 64 Antigen detection for Rapid confirmation of M.tuberculosis isolates

Synthesis of plant-based, self-adjuvanted, dual antigen specific to Mycobacterium tuberculosis as a novel tuberculosis subunit vaccine that elicits immunogenicity in rabbit

OBJECTIVES

The only approved vaccine, Bacillus Calmette Guérin (BCG) used in global tuberculosis (TB) immunization programmes has been very effective in childhood TB but not in adult pulmonary and latent TB. Moreover, the emergence of multi-drug resistance-TB cases demands either to increase efficiency of BCG or replace it with the one with improved efficacy.

RESULTS

A novel combination of two most effective secreted protein antigens specific for Mycobacterium tuberculosis (Mtb), ESAT-6 and MPT-64 (but not present in BCG strains) fused with a cholera toxin B subunit (CTB) and tagged with 6xHis was expressed for the first time in Escherichia coli as well as in transgenic cucumber plants developed using Agrobacterium tumefaciens-mediated transformation. The recombinant fusion protein (His6x.CTB-ESAT6-MPT64) expressed in E. coli was purified by a single-step affinity chromatography and used to produce polyclonal antibodies in rabbit. The transgenic cucumber lines were confirmed by polymerase chain reaction (PCR), Southern blot hybridization, reverse transcriptase PCR (RT-PCR), real-time PCR (qRT-PCR) and expression of recombinant fusion protein by western blot analysis and its quantification by enzyme-linked immunosorbent assay (ELISA). A maximum value of the fusion protein, 478 ng.g^-1 (0.030% of the total soluble protein) was obtained in a transgenic cucumber line. Rabbit immunized orally showed a significant increase in serum IgG levels against the fusion protein as compared to the non-immunized rabbit.

CONCLUSIONS

Stable expression of Mtb antigens with CTB in edible cucumber plants (whose fruits are eaten raw) in sufficient amount possibly would facilitate development of a safe, affordable and orally delivered self-adjuvanted, novel dual antigen based subunit vaccine against TB.

The diagnostic performance of endobronchial ultrasound with Xpert MTB/RIF Ultra in smear-negative pulmonary tuberculosis

OBJECTIVE

This study investigated the diagnostic performance of endobronchial ultrasound with Xpert MTB/RIF Ultra (Ultra) for detecting smear-negative pulmonary tuberculosis (TB).

METHODS

143 patients suspected of sputum smear-negative pulmonary tuberculosis were enrolled in this study in Shanghai Pulmonary Hospital, China. These patients underwent endobronchial ultrasound with a guide sheath (EBUS-GS) or endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) based on their chest CT manifestations. We assessed the sensitivity and specificity of tissue specimens with Ultra in the TB group and non-TB group. Culture and clinical diagnosis were used as gold-standard for TB.

RESULTS

Among these 143 patients, 11 patients were culture-positive TB, 85 patients were diagnosed with culture-negative TB and 47 were with the non-TB diseases. Direct testing with microscopy (Acid-Fast Bacilli smear, AFB), liquid culture, pathology, Xpert MTB/RIF(Xpert) test and Ultra had a sensitivity of 8.3%, 11.5%, 42.7%, 64.6%, and 78.1% individually among all the TB patients. Ultra had a higher sensitivity than Xpert (P = 0.011). But Ultra had a specificity of 59.6% (95% CI 44.3-73.3), lower than that of Xpert (89.4%, 95% CI 76.1-96.0, P = 0.001). Ultra had the same sensitivity on specimens from EBUS-TBNA and EBUS-GS (P = 0.975). Ultra's positive predictive value and negative predictive value were 79.8% and 57.1% respectively.

CONCLUSIONS

Tissue specimens from interventional bronchoscopy combined with Ultra provide a sensitive method for diagnosing smear-negative pulmonary tuberculosis, but its specificity was lower than Xpert.

24 loci MIRU-VNTR analysis and pattern of drug resistance in pre-extensively drug resistant pulmonary tuberculosis in Bangladesh

Phylogenetic diversity and distinct phylogeographic distribution of Mycobacterium tuberculosis (MTB) contribute to regional differences in drug resistance. The emergence of pre-extensively drug resistant tuberculosis (Pre-XDR-TB) becomes obstacles to achieve End TB strategy in Bangladesh. This cross-sectional study was conducted to identify the strains of different lineages of MTB, their variations of distribution among Pre-XDR-TB cases and to observe the linkage of particular strains of MTB with drug resistance. A total of 33 Pre-XDR-TB isolates were enrolled in this study. All isolates were confirmed as MTB by MPT 64 antigen detection and genotyped by 24 loci Mycobacterial Interspersed Repetitive Unit-Variable Number of Tandem Repeats (MIRU-VNTR) analysis. Drug resistance was detected by second line Line probe assay (LPA). Beijing was the predominant strain 16 (48.48%), followed by Delhi/CAS 5(15.15%), LAM 4 (12.12%) and Harlem 3(9.10%), EAI 2(6.06%), Cameroon 2(6.06%) and NEW-1 1(3.03%). There were 31 different genotypes consisting of 2 clusters and 29 singletons. All the clustered strains were belonged to Beijing lineage. Recent transmission occurred manly by Beijing strains, showed low transmission rate (12.1%). Of 33 isolates 30(90.90%) were Fluoroquinolones resistant, the mutations involved was Asp94Gly in gyr A MUT 3C gene 13(39.39%) in quinolone resistance determining region (QRDR) followed by 11 (33.33%) in gyr A MUT 1. Three (9.10%) isolates showed resistant to injectable 2nd line drugs and all mutation occurs in G1484T of rrs MUT 2. Beijing lineage was predominant in treatment failure and relapse cases. Levofloxacin was resistant to all Pre-XDR-TB cases, but moxifloxacin showed low level resistance. QUB 26 was the most discriminatory locus (0.85) among 24 loci whereas MIRU 2 was the least (0.03). 24 loci MIRU-VNTR analysis shows high discriminatory index (0.71), found to be powerful tool for genotyping of Pre-XDR-TB, which is the first study in Bangladesh that enhanced the current TB control policy.

Molecular characterization of Mycobacterium tuberculosis through MPT64 gene polymorphism using next-generation sequencing technology

Aim: To characterize and analyze polymorphism of the MPT64 gene and evaluate AgMPT64-based immunochromatographic assay (ICA) specificity associated with polymorphism. Materials & methods: A total of 1449 suspected samples were tested for tuberculosis (TB), and the MPT64/rv1980c gene was sequenced using next-generation sequencing for polymorphism analysis. Results: Of the TB-positive individuals, 200 (13.80%), 186 (12.84%) and 129 (8.90%) were positive using the liquid culture, GeneXpert and fluorescence microscopy assays, respectively. Liquid culture medium-based samples were confirmed using ICA, in which 193 (96.5%) were positive while seven (3.5%) were negative. Out of 14 sequenced samples, seven were positive and seven negative; 13 were identical to the reference and just one (ICA positive) showed a C477A point mutation (F159L). Conclusion: The results indicate that AgMPT64 can be considered as a potent vaccine candidate.

Tubercular DNA PCR of ocular fluids and blood in cases of presumed ocular tuberculosis: a pilot study

Background:

The definitive diagnosing of ocular tuberculosis (TB) is difficult; therefore, there is a need of better understanding of investigating TB DNA in presumed ocular TB patients.

Objectives:

The aim of this study is to correlate tubercular DNA PCR of aqueous/vitreous and blood in cases of presumed ocular TB.

Design:

A prospective study.

Methods:

DNA was extracted from aqueous of cases of choroidal tuberculoma (group 1) and serpiginous choroiditis (group 2) and from vitreous of cases of vasculitis (group 3) and macular hole/retinal detachment (group 4). Gel-based PCR and real-time PCR amplification were performed using IS6110 primer on ocular fluids. The same was also performed on the blood samples of cases in which tubercular DNA was detected in the ocular fluids.

Results:

Overall, 31 cases were analysed in our study. Tubercular DNA was detected in ocular fluids of seven cases: group 1, two cases (67%); group 2, one case (17%); group 3, four cases (27%); and no case of group 4. Blood samples of six of these seven patients were positive for tubercular DNA. Of these six patients, four had evidence of systemic TB and were on ATT. Two cases had no evidence of active systemic TB, yet PCR was positive from blood and ocular fluids.

Conclusion:

Tubercular DNA detected from ocular fluids may possibly be due to bystander DNA and may not indicate primary ocular tubercular infection. Thus, caution must be exercised prior to labelling a case of uveitis as being tubercular based on the results of molecular assays on ocular fluids alone. The results of PCR on ocular fluids should be correlated with PCR on blood and systemic findings.

Socio-clinico-radiological profile of smear-positive pulmonary tuberculosis patients in association with sputum conversion and baseline hsCRP levels

Our was an observational follow-up study where the aim was to assess the baseline high-sensitivity C-reactive protein levels in 50 smear-positive pulmonary tuberculosis patients in association with socio-clinico-radiological profile and microbiological conversion. Smear and culture conversion of sputum samples at the end of intensive phase of anti-tubercular treatment were recorded. Baseline serum high-sensitivity C-reactive protein estimation was done by ELISA. Mean high-sensitivity C-reactive protein levels at baseline, smear/culture converted and delayed converters were 68.1 ± 22.2 mg/l, 66.7 ± 22.0 mg/l and 91.6 ± 6.7 mg/l, respectively; high-sensitivity C-reactive protein levels were significantly higher in delayed converters as compared to sputum converters. Significantly higher baseline high-sensitivity C-reactive protein levels were seen in patients with bilateral chest X-ray lesions, cavitations, evening rise of temperature, haemoptysis and dyspnoea as compared to those without these features. high-sensitivity C-reactive protein, being a non-specific inflammatory marker could be an adjunct tool for TB prognosis.

NAT2 polymorphisms associated with the development of hepatotoxicity after first-line tuberculosis treatment in Mexican patients: From genotype to molecular structure characterization

BACKGROUND AND AIMS

To assess the relevance of the slow acetylator phenotype based on NAT2 genotypes, among patients with pulmonary tuberculosis (PTB) that developed hepatotoxicity after first-line tuberculosis treatment in a Northeastern Mexican population.

METHODS

Ninety one PTB patients were included, 7 of them developed hepatotoxicity. NAT2 SNPs (rs1801279, rs1041983, rs1801280, rs1799929, rs1799930, rs1208, and rs1799931) were genotyped by TaqMan allelic discrimination assay. Statistical analyses were performed using Epi Info statistical software 7.0 and SHEsisPlus for haplotype reconstruction. The NAT2 slow non-synonymous SNP were studied by molecular dynamic analysis (MDA).

RESULTS

The frequency of the haplotype associated with slow acetylation status for PTB was 58%, and for with hepatotoxicity (PTB-H) represented 42.6%. Three haplotypes, NAT2*5Q, NAT2*5U, NAT2*5Va were exclusively present in seven PTB-H patients, (P = 0.01, P = 0.0006, P = 0.01, respectively). These haplotypes include the combination of two SNPs (I114T + R197Q or I114T + G286E). The effect of the SNPs on protein structure is to disrupt the CoA binding site affecting acetylation activity.

CONCLUSION

Our study provides insight into slow acetylation NAT2 haplotypes associated with hepatotoxicity after first-line tuberculosis treatment, for first time, in a Mexican population. The molecular mechanism acts at the CoA binding site.

Evaluation of classical and rapid methods for isolation and identification of Mycobacterium bovis in cattle in Bulgaria

Bovine tuberculosis is still a serious problem with major economic impact in many countries. The aim of study was to evaluate the diagnostic capabilities of the classical and some modern, rapid methods for isolation and identification of Mycobacterium bovis. In the period 2015-2018 from 29 outbreaks in 10 different regions of Bulgaria, 1193 lymph nodes from slaughtered cattle were examined by pathoanatomical, bacteriological, PCR and immunochromatographic methods. Of the 283 bacterial isolates, 263 were identified as M. bovis - member of the M. tuberculosis complex.

Isolation and Immunological Detection of Mycobacterium Tuberculosis from HIV and Non-HIV Patients in Benue State, Nigeria

BACKGROUND

Immunological techniques are important tools for tuberculosis epidemiology; although its use is underutilized in Nigeria. In this study, we report the epidemiological outlook of Mycobacterium tuberculosis among HIV patients in Benue State, Nigeria.

METHODS

Sputum samples were collected from 425 suspected TB patients from July 2016 to February 2018 and subjected to acid-fast microscopy, GeneXpert MTB/RIF, processed using NALC-NaOH and cultured on Lowenstein-Jensen media. The isolates obtained were identified by SD-Bioline® assay.

RESULTS

The prevalence of TB by acid-fast microscopy was 35(15.9%). The prevalence of TB by acid-fast bacilli was significantly (χ2 = 8.458; P = 0.003) highest among the 15-34 years age group (22.0%) compared with other age groups. TB prevalence was significantly (χ2 = 4.751; P = 0.029) higher among patients from rural areas than those from urban center (23.8% vs 14.1%). GeneXpert assay detected 64(15.1%) TB cases of which patients from rural areas had significantly (χ2 = 8.104; P = 0.017) higher prevalence of TB than patients from urban areas (23.8% vs 12.9%). The overall rifampicin resistance TB was 3.1%. Also, patients from rural areas had significantly (χ2 = 10.625; P = 0.005) higher rifampicin resistance compared with patient from urban areas (8.3% vs 1.3%). Of the 126(29.7%) mycobacterial isolates, 42(33.33%) were identified as MTBC and 84 (66.67%) as NTM by SD-Bioline® assay.

CONCLUSIONS

The study revealed that Mycobacterium tuberculosis infection is still a major public health problem, with relatively high prevalence rate of rifampicin resistance among HIV positive patients. Further studies are needed for early detection and treatment intervention necessary for infection control.

Immune Biomarkers for Diagnosis and Treatment Monitoring of Tuberculosis: Current Developments and Future Prospects

Tuberculosis (TB) treatment monitoring is paramount to clinical decision-making and the host biomarkers appears to play a significant role. The currently available diagnostic technology for TB detection is inadequate. Although GeneXpert detects total DNA present in the sample regardless live or dead bacilli present in clinical samples, all the commercial tests available thus far have low sensitivity. Humoral responses against Mycobacterium tuberculosis (Mtb) antigens are generally low, which precludes the use of serological tests for TB diagnosis, prognosis, and treatment monitoring. Mtb-specific CD4⁺ T cells correlate with Mtb antigen/bacilli burden and hence might serve as good biomarkers for monitoring treatment progress. Omics-based techniques are capable of providing a more holistic picture for disease mechanisms and are more accurate in predicting TB disease outcomes. The current review aims to discuss some of the recent advances on TB biomarkers, particularly host biomarkers that have the potential to diagnose and differentiate active TB and LTBI as well as their use in disease prognosis and treatment monitoring.

Prevalence and Factors Associated with Multidrug-Resistant Tuberculosis (MDR-TB) among Presumptive MDR-TB Patients in Tigray Region, Northern Ethiopia

Background

Tuberculosis (TB) is one of the major public health problems. There are alarming reports of increasing multidrug-resistant tuberculosis (MTR-TB) from various parts of the globe, including Ethiopia. This study was designed to determine the prevalence and factors associated with MDR-TB among presumptive MDR-TB cases in Tigray Regional State, Ethiopia.

Methods

A cross-sectional study was conducted in Tigray Regional State from 2015 to 2016. Two hundred sputum samples were collected, transported, processed using 2% N-acetyl-L-cysteine-sodium hydroxide, and cultured in LJ medium. Besides, the microscopic examination was performed after ZN staining. Moreover, drug susceptibility test was done using molecular line probe assay. Descriptive statistics and binary and multivariable logistic regression were done. A statistical test was regarded as significant when the P value was <0.05.

Results

The prevalence of MDR-TB was found to be 18.5%. About one-fourth (26.5%) of the study participants had sputum smear positive for acid-fast bacilli (AFB). TB culture was positive in 37% of the samples, and rifampicin mono-resistant cases accounted for 3.5% of the presumptive MDR-TB cases. Three (1.5%) were new MDR-TB cases, while the rest had been treated previously for TB. Most (63.5%) of the MDR-TB cases were from 15 to 44 years of age. Age was associated with MDR-TB with a crude odds ratio of 1.06 (CI: 1.02–1.10) and adjusted odds ratio of 1.06 (CI: 1.00–1.11).

Conclusions

The prevalence of MDR-TB was found to be high. Preventive measures should be taken to prevent the transmission of MDR-TB in the community.

Structural dynamics behind variants in pyrazinamidase and pyrazinamide resistance

Pyrazinamide (PZA) is an important component of first-line anti-tuberculosis (anti-TB) drugs. The anti-TB agent is activated into an active form, pyrazinoic acid (POA), by Mycobacterium tuberculosis (MTB) pncA gene encoding pyrazinamidase (PZase). The major cause of PZA-resistance has been associated with mutations in the pncA gene. We have detected several novel mutations including V131F, Q141P, R154T, A170P, and V180F (GeneBank Accession No. MH461111) in the pncA gene of PZA-resistant isolates during PZA drug susceptibility testing followed by pncA gene sequencing. Here, we investigated molecular mechanism of PZA-resistance by comparing the results of experimental and molecular dynamics. The mutants (MTs) and wild type (WT) PZase structures in apo and complex with PZA were subjected to molecular dynamic simulations (MD) at the 40 ns. Multiple factors, including root mean square deviations (RMSD), binding pocket, total energy, dynamic cross correlation, and root mean square fluctuations (RMSF) of MTs and WT were compared. The MTs attained a high deviation and fluctuation compared to WT. Binding pocket volumes of the MTs, were found, lower than the WT, and the docking scores were high than WT while shape complementarity scores were lower than that of the WT. Residual motion in MTs are seemed to be dominant in anti-correlated motion. Mutations at locations, V131F, Q141P, R154T, A170P, and V180F, might be involved in the structural changes, possibly affecting the catalytic property of PZase to convert PZA into POA. Our study provides useful information that will enhance the understanding for better management of TB. AbbreviationsDSTdrug susceptibility testingΔelecelectrostatic energyLJLowenstein-Jensen mediumMGITmycobacterium growth indicator tubesMTsmutantsMDmolecular dynamic simulationsMTBMycobacterium tuberculosisNALC-NaOHN-acetyl-l-cysteine-sodium hydroxideNIHNational Institutes of HealthNPTamount of substance (N), pressure (P) temperature (T)NVTmoles (N), volume (V) temperature (T)PZasepyrazinamidaseΔpspolar solvation energyPTRLProvincial Tuberculosis Reference LaboratoryRMSDroot mean square deviationsRMSFroot mean square fluctuationsΔSASAsolvent accessible surface area energyTBtuberculosisGTotaltotal binding free energyΔvdWVan der Waals energyWTwild typeCommunicated by Ramaswamy H. Sarma.

Heat Inactivation Renders Sputum Safe and Preserves Mycobacterium tuberculosis RNA for Downstream Molecular Tests

The World Health Organization End Tuberculosis (TB) strategy has called for the development of-and increased access to-effective tools for diagnosis and treatment of TB disease. Mycobacterium tuberculosis , the causative agent of TB, is categorized as a highly infectious agent. Consequently, diagnostic tests that involve comprehensive manipulation of specimens from presumed tuberculosis cases must be performed in a category 3 laboratory. We have evaluated the use of heat inactivation to render TB samples safe to work with while preserving RNA for downstream molecular tests. Using Mycobacterium bovis bacillus Calmette-Guérin (BCG) cultures and TB-positive sputum samples, we show that boiling for 20 min at 80, 85, and 95°C inactivates all M. tuberculosis bacilli. The efficiency of inactivation was verified by culturing heat-treated and untreated (live) fractions of BCG and TB sputum samples for 42 days. No growth was observed in the cultures of heat-treated samples. In contrast, the optical density of untreated BCG in Middlebrook 7H9 broth rose from 0.04 to 0.85, and the untreated sputum samples flagged positive at 3 days of incubation in mycobacterial growth indicator tubes. Quantification of reference genes 16S rRNA, transfer-messenger RNA (tmRNA), pre-16S rRNA, and rpoB by reverse transcriptase quantitative PCR (RT-qPCR) showed minimal loss in estimated bacterial load. The loss was RNA species dependent, <1 log₁₀, 1.1 log₁₀, 1.3 log₁₀, and 2.4 log₁₀ estimated CFU/ml for 16S rRNA, tmRNA, pre-16S rRNA, and rpoB, respectively. The RNA loss was independent of inactivation temperature. These findings show that heat inactivation could obviate the need for category 3 laboratories to perform RNA-based testing of TB samples.

A loop-mediated isothermal amplification assay for the diagnosis of pulmonary tuberculosis

Quantitated Mycobacterium tuberculosis (M.tb) H37Rv DNA was used to analyse the sensitivity and the specificity was assessed using DNA isolated from the reference strain H37Rv, 12 nontuberculous mycobacterium (NTM) species and five nonmycobacterium species. Furthermore, performance of the assay was evaluated on the sputum samples and compared with smear microscopy, culture and PCR. mpt64 (also called mpb64 or Rv1980c) loop-mediated isothermal amplification (LAMP) successfully detected 1 pg DNA within 40 min and successfully rejected NTMs and other bacterial species tested. It specifically detected all the 119 confirmed TB cases and 100 of the 104 control cases. The resulting sensitivity and specificity of LAMP assay was found to be 100% (95% CI: 96·79-100%) and 96·15% (95% CI; 90·44-98·94%) respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Loop-mediated isothermal amplification (LAMP) is a technique for isothermal DNA amplification suitable for cost-limited settings as it prevents the use of sophisticated instruments. Using mpt64 antigenic protein gene, we developed a LAMP assay especially for organisms of the M. tuberculosis complex. mpt64 LAMP assay showed 100% sensitivity and detected all the bacteriologically and clinically positive TB cases not detected by smear, culture or PCR methods.

Loop-Mediated Isothermal Amplification for Rapid Identification of Mycobacterium tuberculosis in Comparison with Immunochromatographic SD Bioline MPT64 Rapid® in a High Burden Setting

Loop-mediated isothermal amplification (LAMP) was assessed for rapid identification of Mycobacterium tuberculosis complex (MTC) in comparison with an immunochromatographic test (ICT) using SD Bioline Ag MPT64 Rapid^®. One hundred and fifty-one MGIT cultures positive for acid-fast bacilli were tested for MTC. DNA was extracted from a small portion of culture samples by heat lysis and subjected to LAMP analysis. Of these, 144 were positive and 5 were negative by both tests. One culture that was ICT negative but was LAMP positive was confirmed to have a mutation in the mpt64 gene. The agreement was 98.68% (95% confidence interval [CI]: 94.80-99.77), and the kappa value was 0.83% (95% CI: 0.59-1.00). Good correlation results suggested that LAMP assay is a reliable molecular test for rapid identification of MTC and is practical for use in resource-limited, high burden settings.

Use of an immunochromatographic assay for rapid identification of Mycobacterium tuberculosis complex clinical isolates in routine diagnosis

Accurate identification of Mycobacterium tuberculosis complex (MTBC) isolates is essential for tuberculosis (TB) control, especially in a high-burden country such as Brazil. Conventional identification methods are laborious and time-consuming, while rapid molecular methods are expensive and require skilled personnel and appropriate physical laboratory infrastructure. Immunochromatographic assays (ICAs) have been shown to provide a rapid and reliable TB diagnosis at a low cost. The use of the SD Bioline TB Ag MPT64 ICA (MPT64 assay) for rapid identification of MTBC clinical isolates in the routine diagnosis of a large-volume reference TB laboratory was evaluated. We analysed 375 isolates on solid and liquid media concurrently with conventional phenotypic methods, the PRA-hsp65 molecular technique and the MPT64 assay. The sensitivity, specificity and accuracy of the ICA were 97.7, 100 and 98.1 %, respectively. The MPT64 assay yielded rapid and accurate results, enabling the treatment to be initiated early and also impacting on TB control.

Performance of MTBDRplus assay in detecting multidrug resistant tuberculosis at hospital level

OBJECTIVE

Multidrug-resistant tuberculosis (MDR-TB) case finding progressively increased in Ethiopia mainly as a result of the utilization of World Health Organization (WHO)-endorsed rapid technologies including MTBDRplus assay. However, there is inadequate data on routine testing performance of the MTBDRplus assay. Consequently, the aim of the study was to assess the routine performance of the MTBDRplus assay in detecting MDR-TB at St. Peter's TB Specialized Hospital.

RESULTS

The sensitivity and specificity of MTBDRplus in detecting isoniazid (INH) resistance were 96.3 and 100%, respectively. While for rifampicin (RIF) 100% was recorded for both. Similarly, a sensitivity of 97.96% and a specificity of 100% was measured for detecting MDR-TB. Among 49 MTBDRplus RIF resistant isolates, 46 (93.9%) strains had rpoB mutation. S531L was the most common rpoB mutant (81.6% of RIF resistant cases). All MTBDRplus INH resistant isolates (n = 52) had S315T1 katG mutation.

Solution NMR Studies of Mycobacterium tuberculosis Proteins for Antibiotic Target Discovery

Tuberculosis is an infectious disease caused by Mycobacteriumtuberculosis, which triggers severe pulmonary diseases. Recently, multidrug/extensively drug-resistant tuberculosis strains have emerged and continue to threaten global health. Because of the development of drug-resistant tuberculosis, there is an urgent need for novel antibiotics to treat these drug-resistant bacteria. In light of the clinical importance of M. tuberculosis, 2067 structures of M. tuberculsosis proteins have been determined. Among them, 52 structures have been solved and studied using solution nuclear magnetic resonance (NMR). The functional details based on structural analysis of M. tuberculosis using NMR can provide essential biochemical data for the development of novel antibiotic drugs. In this review, we introduce diverse structural and biochemical studies on M. tuberculosis proteins determined using NMR spectroscopy.

Evaluation of the SD Bioline TB Ag MPT64 test for identification of Mycobacterium tuberculosis complex from liquid cultures in Southwestern Uganda

BACKGROUND

To confirm presence of Mycobacterium tuberculosis complex, some tuberculosis culture laboratories still rely on para-nitrobenzoic acid (PNB), a traditional technique that requires sub-culturing of clinical isolates and two to three weeks to give results. Rapid identification tests have improved turnaround times for mycobacterial culture results. Considering the challenges of the PNB method, we assessed the performance of the SD Bioline TB Ag MPT64 assay by using PNB as gold standard to detect M. tuberculosis complex from acid-fast bacilli (AFB) positive cultures.

OBJECTIVES

The aim of this study was to determine the sensitivity, specificity and turnaround time of the SD MPT64 assay for identification of M. tuberculosis complex, in a setting with high prevalence of tuberculosis and HIV.

METHODS

A convenience sample of 690 patients, with tuberculosis symptoms, was enrolled at Epicentre Mbarara Research Centre between April 2010 and June 2011. The samples were decontaminated using NALC-NaOH and re-suspended sediments inoculated in Mycobacterium Growth Indicator Tubes (MGIT) media, then incubated at 37 °C for a maximum of eight weeks. A random sample of 50 known negative cultures and 50 non-tuberculous mycobacteria isolates were tested for specificity, while sensitivity was based on AFB positivity. The time required from positive culture to reporting of results was also assessed with PNB used as the gold standard.

RESULTS

Of the 138 cultures that were AFB-positive, the sensitivity of the SD MPT64 assay was 100.0% [95% CI: 97.3 - 100] and specificity was 100.0% (95% CI, 96.4 - 100). The median time from a specimen receipt to confirmation of strain was 10 days [IQR: 8-12] with SD MPT64 and 24 days [IQR: 22-26] with PNB.

CONCLUSION

The SD MPT64 assay is comparable to PNB for identification of M. tuberculosis complex and reduces the time to detection.

Evaluation of the GeneXpert MTB/RIF assay on extrapulmonary and respiratory samples other than sputum: a low burden country experience

The aim of this study was to assess the performance of the GeneXpert MTB/RIF assay on extrapulmonary (EP) and respiratory (non-sputum) clinical samples of patients suspected of having tuberculosis (TB) from Queensland, Australia. A total of 269 EP and respiratory (non-sputum) clinical samples collected from Qld patients who were suspected of having TB were subjected to the GeneXpert MTB/RIF analysis, Ziehl-Neelsen (ZN) staining, Mycobacterium tuberculosis (MTB) culture and drug susceptibility testing. Phenotypic and genotypic data were compared. The overall performance analysis of the GeneXpert MTB/RIF assay for detection of MTB complex demonstrated sensitivity of 89%, specificity of 95%, PPV of 89% and NPV of 95% using culture as a reference standard. The GeneXpert MTB/RIF analysis of acid-fast bacilli (AFB) smear positive samples and AFB smear negative samples showed sensitivities of 100% and 77%, respectively. Looking at individual EP and respiratory (non-sputum) sample types, the sensitivity ranged from 60% to 100% although the specificity ranged from 33% to 100% with the specificity of lymph node tissue biopsy being the lowest. The GeneXpert MTB/RIF assay detected 11% more TB cases than culture and 27% more cases than ZN microscopy. Due to insufficient numbers of presenting rifampicin resistance cases, performance analysis of the GeneXpert MTB/RIF assay on rifampicin resistance could not be carried out. The GeneXpert MTB/RIF assay is potentially valuable for TB diagnosis in the majority of the EP and respiratory (other than sputum) samples in our setting. Although the GeneXpert MTB/RIF assay provides rapid diagnostic results, the overall sensitivity to rule out the disease is suboptimal for some specimen types. Performance varied according to specimen type and AFB smear status. The sensitivity and specificity of lymph node tissue was 63% and 33%. Care must be taken when using the GeneXpert MTB/RIF assay for detection of MTB in lymph node tissue samples. All samples should be cultured regardless of the GeneXpert MTB/RIF assay result.

Prevalence of multidrug-resistant tuberculosis cases among HIV-positive and HIV-negative patients eligible for retreatment regimen in Togo using GeneXpert MTB/RIF

Drug-resistant tuberculosis (TB) is emerging as an important health problem in Togo. From sputum of previously treated TB patients, multidrug-resistant (MDR) TB was diagnosed in 24% (10/42) patients via GeneXpert MTB/RIF compared to 25% (6/24) patients via conventional drug susceptibility testing (BACTEC MGIT 960 system). The agreement between these two methods to detect MDR-TB is excellent. However, GeneXpert MTB/RIF offers the advantage of rapidly detecting Mycobacterium tuberculosis complex in sputum samples in instances where the cultures are negative (33%, 14/42) or contaminated (9.5%, 4/42). GeneXpert MTB/RIF permitted us to estimate the prevalence of MDR-TB in previously treated TB patients and to improve TB diagnostics among HIV-positive and -negative patients in Togo, where culturing M. tuberculosis complex from sputum samples is challenging.

Evaluación de la técnica BD MGITTM TBc® para identificación del complejo Mycobacterium tuberculosis

<p><strong>Objetivo</strong> Evaluar la técnica BD MGIT^TM TBc^® para identificación del complejo<em> Mycobacterium tuberculosis </em>a partir de aislamientos en medio de cultivo sólido y líquido.</p><p><strong>Materiales y Métodos</strong> Se desarrolló un estudio descriptivo, donde se analizaron 117 aislamientos por la técnica de inmucromatografía a partir de cultivos en medio sólido y líquido para identificación del complejo <em>Mycobacterium tuberculosis</em>. Se calculó coeficiente kappa para determinar el grado de acuerdo entre los dos métodos. Cuando hubo diferencia de resultados estos se confirmaron mediante pruebas convencionales. La herramienta empleada para el análisis de datos fue Epidat 3.1.</p><p><strong>Resultados</strong> La metodología BD MGIT^TM TBc^® realizada a partir de cultivos en medio sólido y líquido, presentó un grado de acuerdo excelente con un coeficiente kappa de 0,84.</p><p><strong>Conclusión</strong> La técnica BD MGIT^TM TBc^® realizada a partir de cultivos en medio sólido, para la identificación del complejo<em> Mycobacterium tuberculosis,</em> presenta excelente concordancia, comparada con los resultados obtenidos en medio de cultivo líquido. El Laboratorio Nacional de Referencia recomienda el uso de esta técnica para la identificación de especie en medio de cultivos sólidos.</p>

Rapid identification of Mycobacterium tuberculosis complex in clinical isolates by combining presumptive cord formation and MPT64 Antigen Immunochromatographic Assay

PURPOSE

Combining the results of presumptive cord formation in smear and MPT64 Antigen Immunochromatographic Assay has been suggested to reduce the false negative and positive rates for identification of Mycobacterium tuberculosis (MTB) complex in liquid culture. This study was done to evaluate the clinical utility of combining the results of the two tests for rapid identification MTB complex in mycobacterial isolates.

METHODS

484 isolates of mycobacteria obtained in MGIT culture were identified using presumptive cord formation in smear and further by MPT64 Antigen ICT assay. Result obtained were analyzed taking PNB inhibition test as the reference standard.

RESULTS

Combining the results of the two tests, 464 (95.9%) isolates were correctly identified while discrepant results were obtained in 20 (4.1%) isolates. When the results of the two tests were intersected, the specificity and PPV was 100%, but the sensitivity decreased to 96.4% and the NPV to 68.6%. On the other hand, when the results of the two methods were combined, the sensitivity and NPV was 100%, but the specificity decreased to 88.6% and the PPV to 99.1%.

CONCLUSION

Presumptive cord formation and MPT64 antigen ICT assay can be used in combination for identification of MTB complex. When both the test are positive, the culture can be reported to contain MTB complex. If both the tests are negative, the culture should be reported to contain NTM. Only when discrepant results are obtained by the two tests, further evaluation is necessary to ensure an accurate diagnosis.

Extra pulmonary tuberculosis: rapid identification of Mycobacterium tuberculosis grown in Mycobacterium growth indicator tube 960 and Lowenstein-Jensen media, employing Standard diagnostics Bioline Mycobacterium tuberculosis protein 64 antigen detection kit

BACKGROUND

Investigation of extra pulmonary tuberculosis (EPTB) in and around Pondicherry is being carried out since August 2011 in our tertiary care super specialty hospital.

OBJECTIVES

To compare the rapid Kit SD Bio-Line MPT 64 Ag with conventional and time consuming biochemical tests. Confirmation of Mycobacterium tuberculosis at a reasonable time frame is the main thrust.

MATERIALS AND METHODS

Thirty three Mycobacterium tuberculosis and four Non-Tuberculous Mycobacteria (NTM) grown in MGIT960 system/Lowenstein-Jensen media (LJ) were examined by the rapid MPT 64 antigen detection as well as a battery of conventional tests like niacin, nitrate reduction, paraminobenzoic acid susceptibility and cord formation.

RESULTS AND CONCLUSION

. Both the rapid kit and conventional tests correctly identified 33 M.tuberculosis isolates. Keeping conventional identification as reference, sensitivity and specificity for rapid kit was 100%. Rapid kit which takes only 15 minutes is accurate, cost effective, and facilitates early treatment for these EPTB patients, whose clinical specimens are paucibacillary.

[The new tools of microbiological diagnosis of tuberculosis]

This review focuses on the role of new tools in the "modern" microbiological diagnosis of tuberculosis. Traditional techniques of microscopy and culture remain essential to diagnostic certainty, but some innovations replace daily the older techniques such as the identification of Mycobacterium tuberculosis complex by immunochromatography or mass spectrometry MALDI-TOF type from positive cultures, or susceptibility testing in liquid medium. New tools that use molecular techniques have become important. They all have in common to optimize the fight against tuberculosis by reducing diagnostic delay. They also allow rapid detection of drug resistance. However, the techniques of gene amplification directly from clinical samples are still less sensitive than culture. Bacteriological diagnosis of tuberculosis disease therefore still relies on the complementarities of different phenotypic and molecular techniques.

Rapid Immunochromatographic Test for the Identification and Discrimination of Mycobacterium tuberculosis Complex Isolates from Non-tuberculous Mycobacteria

BACKGROUND

A new rapid Immunochromatographic test (ICT) kit (SDBioline TB Ag MPT64RAPID(®)) developed by Standard Diagnostics, South Korea was evaluated for rapid differentiation of M. tuberculosis from non tuberculous mycobacteria (NTM). It detects MPT 64 antigen in M. tuberculosis isolates using mouse monoclonal MPT 64 antibody. The kit was assessed for routine identification of the Acid Fast Bacilli(AFB) isolated in our laboratory.

MATERIALS AND METHODS

Two hundred eight culture isolates of Mycobacteria were tested using ICT test kit for detection of MPT 64 antigen from liquid and solid culture. H37Rv strain was employed as the positive reference control. Any negative result was referred for confirmation by Gen Probe Accu Probe assay for MTB Complex (Gen-Probe, San Diego, Calif.). Speciation of NTM was performed using genotypic Mycobacterium CM assay (Hain's life sciences, Germany).

RESULTS

Of the 208 culture positive isolates tested, 182 (87.5%) were found positive for Mycobacterium tuberculosis Complex and remaining 26 (12.5%) were considered as NTM. These results were further confirmed by Gen Probe Accu probe assay that served as the reference method for detection of MTBC. H37Rv reference strain was taken as a control for ICT test and molecular tests. The reference strain showed the presence of MPT64 antigen band in the ICT test. Similar bands were formed in all MTBC (182) isolates tested, proving 100 per cent sensitivity and no bands were detected in 48 (100%) NTM isolates tested, proving 100 per cent specificity of the ICT kit.

CONCLUSION

Tuberculosis is a global pandemic. Rapid identification of Mycobacteria as MTB complex or non-tuberculous Mycobacteria from culture is important for treatment of infected cases and drug susceptibility testing of the culture isolate. MPT 64 TB antgen detection using SD Bioline Immunochromatographic test is a simple and cost effective method for differentiation of Mycobacterial cultures as MTB complex from non- tuberculous Mycobacteria.

Drug Resistance Pattern of MTB Isolates from PTB Patients

Background. TB is a global pandemic disease. All TB control programs were not successful due to the emergence of multidrug resistance in M. tuberculosis strains. Objective of the present study was to detect the rate of MDR-MTB in this part of India. Methods. One hundred and thirty clinical MTB strains isolated from patients on treatment and confirmed as MTB by MPT64 antigen detection were tested for drug susceptibility against Streptomycin, INH, Rifampicin, and Ethambutol by MBBact automated system. Result. Thirty-two were MDRs (25.61%). 31.2%, 28%, 17.6%, and 21.6% were resistant to INH, RIF, Ethambutol, and Streptomycin, respectively. Resistance to either INH or Rifampicin was 20.8% and 13.88%, respectively. Combined INH and Rifampicin resistance was seen in 18.05% isolates. Conclusion. Drug resistance rate is high in patients treated previously and who have been irregular on treatment.

Tuberculosis diagnosis using immunodominant, secreted antigens of Mycobacterium tuberculosis

Tuberculosis (TB) remains a major public health concern in most low-income countries. Hence, rapid and sensitive TB diagnostics play an important role in detecting and preventing the disease. In addition to established diagnostic methods, several new approaches have been reported. Some techniques are simple but time-consuming, while others require complex instrumentation. One prominent and readily available approach is to detect proteins that Mycobacterium tuberculosis secretes, such as Mpt64, the 6-kDa early secreted antigenic target (Esat6), the 10-kDa culture filtrate protein (Cfp10), and the antigen 85 (Ag85) complex. Although their functions are not fully understood, a growing body of molecular evidence implicates them in M. tuberculosis virulence. Currently these biomarkers are either being used or investigated for use in skin patch tests, biosensor analyses, and immunochromatographic, immunohistochemical, polymerase chain reaction-based, and enzyme-linked immunosorbent assays. This review provides a comprehensive discussion of the roles these immunodominant antigens play in M. tuberculosis pathogenesis and compares diagnostic methods based on the detection of these proteins with more established tests for TB.

Utility and diagnostic performance of Mycobacterium tuberculosis complex by two immunochromatographic assays as compared with the molecular Genotype assay in Nigeria

Among the disadvantages of smear microscopy for detection of tuberculosis cases is its inability to differentiate between Mycobacterium tuberculosis (MTB) and non-tuberculous mycobacteria (NTM). This study evaluated two, new immunochromatographic assays - Capilia TB-Neo and SD Bioline - on unheated and heated cultures at 80°C for 30min respectively for their ability to discriminate between MTB complex and NTM as compared with the molecular Genotype assay. Mycobacteria used in the study were obtained from smear-positive specimens collected from patients at four major hospitals in Cross River State, Nigeria. Capilia TB-Neo and SD Bioline showed sensitivities of 98.8% and 93.8% respectively and 100% specificity for both assays. Heating the isolates did not significantly impact the test performance. Both tests are recommended for use in rapid differentiation of strains isolated in Nigeria.

Immunochromatographic assays for detection of Mycobacterium tuberculosis: what is the perfect time to test?

In this study, we aimed to correlate the analytical performance of SD BIOLINE TB Ag MPT64 Rapid Test kit (MPT64 assay) with the mycobacterial growth unit (GU) reported by the BACTEC MGIT 960 (MGIT 960) instrument. A total of 394 culture isolates reported positive by MGIT 960 were processed daily (until 'day 4') with the MPT64 assay until a positive MPT64 result was obtained and their GU values were noted daily before MPT64 testing. Based on this correlation of MPT64 positivity and corresponding GU values, a GU cut-off was determined. In the validation phase, with the experimentally determined GU cut-off value, 99.1% (576/581) of culture isolates were correctly identified as MTB within 2 days from instrument positivity. All results were available using a single-MPT64 assay strip, making the assay cost-effective. Thus, systematic implementation of the MPT64 assay proved to be cost-effective in a high-throughput laboratory without any delay in patient reporting.

Evaluation of an immunochromatographic test for discrimination between Mycobacterium tuberculosis complex & non tuberculous mycobacteria in clinical isolates from extra-pulmonary tuberculosis

BACKGROUND & OBJECTIVES

Accurate diagnosis of tuberculosis (TB) is crucial to facilitate early treatment of the patients, and to reduce its spread. Clinical presentation of Mycobacterium tuberculosis complex (MTBC) and non tuberculous mycobacteria (NTM) may or may not be the same, but the treatment regimen is always different for both the infections. Differentiation between MTBC and NTM by routine laboratory methods is time consuming and cumbersome. This study was aimed to evaluate an immunochromatographic test (ICT), based on mouse monoclonal anti-MPT64, for simple and rapid discrimination between MTBC and NTM in clinical isolates from extra-pulmonary tuberculosis cases.

METHODS

A total of 800 clinical samples were collected from patients suspected to have extra-pulmonary tuberculosis. Preliminary diagnosis has been done by direct Ziehl-Neelsen (ZN) staining followed by culture in BACTEC system. A total of 150 clinical isolates, which were found positive in BD 460 TB system during September 2009 to September 2010 were selected for the screening by ICT test. p-nitro-α-acetylamino- β-hydroxy propiophenone (NAP) test was performed for differentiation of MTBC and NTM. M. tuberculosis complex was further confirmed by IS6110 PCR of BACTEC culture positive isolates, this served as the reference method for MTBC identification and comparative evaluation of the ICT kit.

RESULTS

Of the 150 BACTEC culture positive isolates tested by ICT kit, 101 (67.3%) were found positive for MTBC and remaining 49 (32.7%) were considered as NTM. These results were further confirmed by IS6110 PCR that served as the reference method for detection of MTBC. H 37 Rv reference strain was taken as a control for ICT test and IS6110 PCR. The reference strain showed the presence of MPT64 antigen band in the ICT test. Similar bands were formed in 101 of 102 MTBC isolates tested, proving 99.1 per cent sensitivity and no bands were detected in 48 (100%) NTM isolates tested, proving 100 per cent specificity of the ICT kit.

INTERPRETATION & CONCLUSIONS

Our findings show that ICT test can be used on direct culture positive specimens. It does not require any special equipment, is simple and less time consuming. It can easily discriminate between MTBC and NTM and thus can help in appropriate management of tuberculosis.

Performance of the MGIT TBc identification test and meta-analysis of MPT64 assays for identification of the Mycobacterium tuberculosis complex in liquid culture

Rapid MPT64-based immunochromatographic tests (MPT64 ICTs) have been developed to detect Mycobacterium tuberculosis complex (MTBC) in culture. We demonstrated the noninferiority of one commercial MTP64 ICT, the MGIT TBc identification (TBcID) test, to GenoType line probe assays for MTBC identification in positive MGIT cultures. Meta-analysis of MPT64 ICT performance for identification of MTBC in liquid culture confirmed similar very high sensitivities and specificities for all three commercial MPT64 assays for which sufficient data were available.