Evaluation of the Capilia TB assay for culture confirmation of Mycobacterium tuberculosis infections in Zambia and South Africa

MPT64 assays for the rapid detection of Mycobacterium tuberculosis

Background

Tuberculosis (TB) is a serious infectious disease caused by Mycobacterium tuberculosis (MTB). An estimated 1.7 billion people worldwide are infected with Mycobacterium tuberculosis (LTBI) during the incubation period without any obvious symptoms. Because of MTB’s high infection and mortality rates, there is an urgent need to develop a fast, portable, and sensitive diagnostic technology for its detection.

Methods

We included research from PubMed, Cochrane Library, Web of Science, and Embase and extracted the data. MetaDisc and STATA were used to build forest plots, Deek’s funnel plot, Fagan plot, and bivariate boxplot for analysis.

Results

Forty-six articles were analyzed, the results of which are as follows: sensitivity and specificity were 0.92 (0.91–0.93) and 0.95 (0.94–0.95) respectively. The NLR and PLR were 0.04 (95% CI 0.03–0.07) and 25.32 (95% CI 12.38–51.78) respectively. DOR was 639.60 (243.04–1683.18). The area under the SROC curve (AUC) was 0.99.

Conclusions

MPT64 exhibits good diagnostic efficiency for MTB. There is no obvious heterogeneity between the three commercial kits.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06022-w.

Diagnosis of rifampicin-resistant tuberculosis: Discordant results by diagnostic methods

The performance of the Xpert© MTB/RIF and MTBDRplus assays for the detection of rifampicin resistant Mycobacterium tuberculosis was compared to culture-based drug susceptibility testing in 30 specimens with rifampicin-resistant and rifampicin-indeterminate Xpert MTB/RIF results collected between March 2012 and March 2014. Xpert MTB/RIF and MTBDRplus were 100% sensitive and 100% concordant for rifampicin resistance detection, but 3 of 13 samples (23%) positive for rifampicin resistance on Xpert MTB/RIF and MTBDRplus were negative for rifampicin resistance on mycobacteria growth indicator tube drug susceptibility testing. Specificity was 72% for Xpert MTB/RIF and 80% for MTBDRplus. Positive predictive value for Xpert MTB/RIF for multidrug resistant tuberculosis was 47.8% for new patients and 77.8% for previously treated patients; negative predictive value was 100% for both new and previously treated patients. The discordant rifampicin resistance test results indicate a need to fully characterise circulating rifampicin resistant Mycobacterium tuberculosis strains in Zambia and to inform the development of guidelines for decision-making in relation to diagnosis of drug-resistant tuberculosis.

Rapid identification of mycobacteria from positive MGIT broths of primary cultures by MALDI-TOF mass spectrometry

Background

Rapid identification of mycobacteria is important for timely treatment and the implementation of public health measures. The MGIT system ensures rapid detection of mycobacteria, but identification is usually delayed by days to weeks due to further subculture on solid medium. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) was demonstrated to effectively identify mycobacteria isolates subcultured from solid or liquid media. Reports of identification directly from MGIT broths of both sterile and non-sterile clinical specimens, omitting the subculture step, were limited and not satisfactory before. Our identification method dramatically shortened delay from detection to identification of mycobacteria.

Methodology

We assessed the performance of the Vitek MS IVD version 3.0 for direct identification of NTM and M.tuberculosis from primary MGIT cultures, and assessed two sample preparation methods.

Results

Direct identification of NTM from positive MGIT broths, using MALDI-TOF VITEK MS with IVD v.3.0, generated high rates of acceptable results reaching 96.4% (80/83), and up to 100% (83/83) for sample preparations including a 0.1% SDS washing step. The sensitivity of VITEK MS to identify M.tuberculosis from MGIT tubes was 58/72 (80.6%), when using immunochromatography (ICA) test as gold standard. A characteristic colony clumping, wool-like appearance was observed in 48, and all 58 (100%) were correctly identified as M.tuberculosis using MALDI-TOF. The detection rate of M.tuberculosis complex was low (10/24, 41.6%) in the 24 MGIT tubes that was polymicrobial. Our method significantly reduced both the reagent cost and turnaround time.

Conclusions

Based on a simplified protocol, we showed that MALDI-TOF MS can be used for rapid identification of NTM directly from primary MGIT cultures within the routine clinical laboratory workflow. However, we recommend an initial ICA test to screen for M.tuberculosis complex, due to a low identification rate of M. tuberculosis in the presence of polymicrobial cultures using MALDI-TOF.

[Identification of Mycobacteria isolated from AIDS patients]

Obstract: To identify Mycobacteria isolated from AIDS patients and to evaluate the diagnostic value of MBP64 antigen Colloidal Gold Diagnostic Kit in distinguishing Mycobacterium tuberculosis(MTB) and Nontuberculous mycobacteria (NTM). Methods: A total of 140 Mycobacteria isolates from AIDS patients were collected and identified by using 16SrDNA PCR assay as well as immune colloidal gold technique (MBP64 antigen Colloidal Gold Diagnostic Kit). The sensitivity and specificity of Colloidal Gold method was analyzed. Results: With the results of 16SrDNA PCR assay as gold standard, the sensitivity and specificity of Colloidal Gold method in distinguishing MTB and NTM were 96.00% and 96.84%, respectively. Among 140 samples, 114 were identified by 16SrDNA PCR assay, among which 50 (43.86%) were identified as MTB, and 63 (55.26%) were identified as NTM. The most popular NTM in AIDS patients were Mycobacterium gordonae, Mycobacterium avium and Mycobacterium kansasii. Conclusion: NTM is of high prevalence in AIDS patients, and MBP64 antigen Colloidal Gold Diagnostic Kit can be used as an effective technique in distinguishing NTM and MTB.

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.

Comparison of MGIT and Myco/F lytic liquid-based blood culture systems for recovery of Mycobacterium tuberculosis from pleural fluid

The specificities and sensitivities of the Bactec mycobacterial growth indicator tube (MGIT) system for the recovery of Mycobacterium tuberculosis from pleural fluid are not statistically different than those of the Myco/F lytic liquid culture system. The time to positivity is shorter in the MGIT system (12.7 versus 20.7 days, respectively; P=0.007). The Myco/F lytic culture system may be an alternative to the MGIT system for diagnosing pleural tuberculosis.

Comparison of an in-house multiplex PCR with two commercial immuno-chromatographic tests for rapid identification and differentiation of MTB from NTM isolates

BACKGROUND

Species specific diagnosis of mycobacterial infection is crucial because treatment of infections caused by Mycobacterium tuberculosis (MTB) differs from that of non-tuberculous mycobacterial (NTM) species. The species identification used to be cumbersome and non-reproducible a decade ago.

OBJECTIVES

Recently, some commercial tests have been made available to differentiate the MTB and NTM growths in culture media. Sensitivity and specificity of these tests was evaluated.

MATERIALS AND METHODS

In this double blind study 572 clinical samples were cultured in an automated BACTEC-MGIT-960 system. A total of 147 (25.7%) samples were MGIT culture positive. These cultures were subjected to an in-house m-PCR (which amplifies hsp-65, esat-6 and ITS region for MAC), two commercial immune-chromatographic tests (ICTs) and phenotypic tests.

RESULTS

Of the 147 MGIT positive cultures, m-PCR was able to correctly identify MTB in 123 cultures and NTM in 24 which included 3 MAC isolates. m-PCR showed 100% agreement with two gold standard methods-the nitrate reductase assay and PNB tests-in correctly identifying MTB. Commercial strips were able to correctly identify MTB in 120 (97.5%) of 123 cultures, while 3 (2.5%) isolates were falsely identified as NTM. However, none of the growth negative spent medium gave false positive results in any of the tests. None of the commercial strips misidentified any of the 24 NTM as MTB; hence, specificity of these strips was 100%. Of the 2 IC test systems, both SD Bioline and BD TBc strip tests missed 2.5% of MTB isolates and misidentified these as NTM.

CONCLUSION

The in-house m-PCR was found to be the most accurate and efficient tool for identifying the MTB, MAC and other NTMs.

Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex

BACKGROUND

The rapid identification of acid-fast bacilli recovered from patient specimens as Mycobacterium tuberculosis complex (MTC) is critically important for accurate diagnosis and treatment. A thin-layer immunochromatographic (TLC) assay using anti-MPB64 or anti-MPT64 monoclonal antibodies was developed to discriminate between MTC and non-tuberculosis mycobacteria (NTM). Capilia TB-Neo, which is the improved version of Capilia TB, is recently developed and needs to be evaluated.

METHODS

Capilia TB-Neo was evaluated by using reference strains including 96 Mycobacterium species (4 MTC and 92 NTM) and 3 other bacterial genera, and clinical isolates (500 MTC and 90 NTM isolates). M. tuberculosis isolates tested negative by Capilia TB-Neo were sequenced for mpt64 gene.

RESULTS

Capilia TB-Neo showed 100% agreement to a subset of reference strains. Non-specific reaction to M. marinum was not observed. The sensitivity and specificity of Capilia TB-Neo to the clinical isolates were 99.4% (99.6% for M. tuberculosis, excluding M. bovis BCG) for clinical MTC isolates and 100% for NTM isolates tested, respectively. Two M. tuberculosis isolates tested negative by Capilia TB-Neo: one harbored a 63-bp deletion in the mpt64 gene and the other possessed a 3,659-bp deletion from Rv1977 to Rv1981c, a region including the entire mpt64 gene.

CONCLUSIONS

Capilia TB-Neo is a simple, rapid and highly sensitive test for identifying MTC, and showed better specificity than Capilia TB. However, Capilia TB-Neo still showed false-negative results with mpt64 mutations. The limitation should be recognized for clinical use.

Assessment of the BD MGIT TBc identification test for the detection of Mycobacterium tuberculosis complex in a network of mycobacteriology laboratories

We evaluate the performance of the TBcID assay in a panel of 100 acid-fast bacilli cultures. Sixty-four isolates were TBcID positive for Mycobacterium tuberculosis complex (MTBC), whereas 36 gave negative results. These included 28 nontuberculous mycobacteria, one nonmycobacterial isolate, one M. tuberculosis, and six M. bovis BCG strains. This corresponds to a sensitivity of 90.14%, specificity of 100%, and positive and negative predictive values of 100% and 80.55%, respectively. The test is rapid, easy to perform and interpret, and does not require sample preparation or instrumentation. However, a negative result does not exclude the presence of a strain belonging to MTBC, especially when mutations in mpb64 gene are present or some M. bovis BCG strains are isolated. The TBcID showed potential to assist in the identification of MTBC when the implementation and usage of molecular methods are often not possible, principally in resource-limited countries.

Sensitivity, specificity, and reproducibility of the Capilia TB-Neo assay

The performance of the Capilia TB-Neo assay, a new-generation assay, was assessed by determining its sensitivity, specificity, reproducibility, and cross-reaction with contaminating organisms. The sensitivity and specificity were 99.2 and 96.4% and 89.3 and 100% in pure and mixed-culture isolates, respectively. The kappa statistic was 95.0 and 77.9% in pure and mixed culture isolates, respectively. There was no cross-reaction with contaminating organisms.

Survey of the diagnostic retooling process in national TB reference laboratories, with special focus on rapid speciation tests endorsed by WHO in 2007

Background

Successful integration of new diagnostics in national tuberculosis (TB) control programs, also called ‘retooling’, is highly dependent on operational aspects related to test availability, accessibility and affordability. This survey aimed to find out whether recommendations to use new diagnostics lead to successful retooling in high TB endemic countries, using immunochromatographic tests (ICTs) for TB culture speciation as a case study. ICTs are recommended to accurately confirm the presence of bacteria of the Mycobacterium tuberculosis complex in liquid culture isolates.

Methods and Findings

Questionnaires were sent to national TB reference laboratories (NRLs) in 42 high TB endemic countries to address their access to information on ICT implementation, logistics related to availability, accessibility and affordability of ICTs, and testing algorithms. Results from 16 responding countries indicated that half of the NRLs were aware of the contents of WHO guidance documents on liquid culture and ICT implementation, as well as their eligibility for a negotiated pricing agreement for ICT procurement. No major issues with availability and accessibility of ICTs were raised. When asked about testing algorithms, ICTs were not used as stand-alone or first test for TB culture identification as recommended by WHO.

Conclusions

The low response rate was a limitation of this survey and together with NRLs managers' unawareness of global guidance, suggests a lack of effective communication between partners of the global laboratory network and NRLs. TB tests could become more affordable to high TB endemic countries, if the possibility to negotiate lower prices for commercial products is communicated to them more successfully. NRLs need additional guidance to identify where available technologies can be most usefully implemented and in what order, taking into account long-term laboratory strategies.

Evaluation of Capilia TB assay for rapid identification of Mycobacterium tuberculosis complex in BACTEC MGIT 960 and BACTEC 9120 blood cultures

Background

Capilia TB is a simple immunochromatographic assay based on the detection of MPB64 antigen specifically secreted by the Mycobacterium tuberculosis complex (MTC). Capilia TB was evaluated for rapid identification of MTC from BACTEC MGIT 960 and BACTEC 9120 systems in Kampala, Uganda. Since most studies have mainly dealt with respiratory samples, the performance of Capilia TB on blood culture samples was also evaluated.

Methods

One thousand samples from pulmonary and disseminated tuberculosis (TB) suspects admitted to the JCRC clinic and the TB wards at Old Mulago hospital in Kampala, Uganda, were cultured in automated BACTEC MGIT 960 and BACTEC 9120 blood culture systems. BACTEC-positive samples were screened for purity by sub-culturing on blood agar plates. Two hundred and fifty three (253) samples with Acid fast bacilli (AFB, 174 BACTEC MGIT 960 and 79 BACTEC 9120 blood cultures) were analyzed for presence of MTC using Capilia TB and in-house PCR assays.

Results

The overall Sensitivity, Specificity, Positive and Negative Predictive values, and Kappa statistic for Capilia TB assay for identification of MTC were 98.4%, 97.6%, 97.7%, 98.4% and 0.96, respectively. Initially, the performance of in-house PCR on BACTEC 9120 blood cultures was poor (Sensitivity, Specificity, PPV, NPV and Kappa statistic of 100%, 29.3%,7%, 100% and 0.04, respectively) but improved upon sub-culturing on solid medium (Middlebrook 7H10) to 100%, 95.6%, 98.2%, 100% and 0.98, respectively. In contrast, the Sensitivity and Specificity of Capilia TB assay was 98.4% and 97.9%, respectively, both with BACTEC blood cultures and Middlebrook 7H10 cultured samples, revealing that Capilia was better than in-house PCR for identification of MTC in blood cultures. Additionally, Capilia TB was cheaper than in-house PCR for individual samples ($2.03 vs. $12.59, respectively), and was easier to perform with a shorter turnaround time (20 min vs. 480 min, respectively).

Conclusion

Capilia TB assay is faster and cheaper than in-house PCR for rapid identification of MTC from BACTEC MGIT 960 and BACTEC 9120 culture systems in real-time testing of AFB positive cultures.

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.

Evaluation of the Bactec MGIT 960 system in combination with the MGIT TBc identification test for detection of Mycobacterium tuberculosis complex in respiratory specimens

The sensitivity and specificity of the MGIT TBc identification (TBc ID) test for Mycobacterium tuberculosis complex (MTC) detection in positive Bactec MGIT cultures were 95.2% and 99.2%, respectively. When MTC-positive results obtained from two additional molecular methods were included, the sensitivity of the MGIT TBc ID test was 85.4%, while that of culture was 95.7%.

High prevalence of pulmonary tuberculosis and inadequate case finding in rural western Kenya

RATIONALE

Limited information exists on the prevalence of tuberculosis and adequacy of case finding in African populations with high rates of HIV.

OBJECTIVES

To estimate the prevalence of bacteriologically confirmed pulmonary tuberculosis (PTB) and the fraction attributable to HIV, and to evaluate case detection.

METHODS

Residents aged 15 years and older, from 40 randomly sampled clusters, provided two sputum samples for microscopy; those with chest radiograph abnormalities or symptoms suggestive of PTB provided one additional sputum sample for culture.

MEASUREMENTS AND MAIN RESULTS

PTB was defined by a culture positive for Mycobacterium tuberculosis or two positive smears. Persons with PTB were offered HIV testing and interviewed on care-seeking behavior. We estimated the population-attributable fraction of HIV on prevalent and notified PTB, the patient diagnostic rate, and case detection rate using provincial TB notification data. Among 20,566 participants, 123 had PTB. TB prevalence was 6.0/1,000 (95% confidence interval, 4.6-7.4) for all PTB and 2.5/1,000 (1.6-3.4) for smear-positive PTB. Of 101 prevalent TB cases tested, 52 (51%) were HIV infected, and 58 (64%) of 91 cases who were not on treatment and were interviewed had not sought care. Forty-eight percent of prevalent and 65% of notified PTB cases were attributable to HIV. For smear-positive and smear-negative PTB combined, the patient diagnostic rate was 1.4 cases detected per person-year among HIV-infected persons having PTB and 0.6 for those who were HIV uninfected, corresponding to case detection rates of 56 and 65%, respectively.

CONCLUSIONS

Undiagnosed PTB is common in this community. TB case finding needs improvement, for instance through intensified case finding with mobile smear microscopy services, rigorous HIV testing, and improved diagnosis of smear-negative TB.

Evaluation of the rapid MGIT TBc identification test for culture confirmation of Mycobacterium tuberculosis complex strain detection

A culture confirmation test for the detection of Mycobacterium tuberculosis complex strains that uses a lateral-flow immunochromatographic assay to detect the MPB64 antigen, the MGIT TBc identification (TBc ID) test, has been developed. We evaluated the performance of the TBc ID test in the detection of the M. tuberculosis complex in 222 primary-positive liquid cultures. We compared these results to those of nucleic acid-based identification and conventional biochemical tests. The validity of the TBc ID test was determined, and all of the nontuberculous mycobacteria (NTM) and Nocardia species tested were found to be negative. The detection limit of the TBc ID test was 5 × 10(5) CFU/ml, and for IS6110 real-time PCR it was 5 CFU/ml. All of the M. tuberculosis and M. africanum cultures were found to be positive, while M. bovis and M. bovis BCG cultures were negative. With the exception of 1 contaminated culture, the 221 culture-positive isolates contained 171 (77.5%) M. tuberculosis isolates, 39 (17.6%) NTM species, and 11 (5.0%) unidentified species. Two culture-positive isolates harbored a 63-bp deletion at position 196 of the mpb64 gene. The sensitivity, specificity, positive predictive values, and negative predictive values of the TBc ID test were 98.8, 100, 100, and 95.1%, respectively. Furthermore, the approximate turnaround time for real-time PCR was 4 h (including buffer and sample preparation), while for the TBc ID test it was less than 1 h. We suggest an algorithm for the primary identification of M. tuberculosis in liquid culture using the TBc ID test as an alternative to conventional subculture followed by identification using biochemical methods.

Malignant mixed müllerian tumor of the uterus. Features favoring its origin from a common cell clone and an epithelial-to-mesenchymal transformation mechanism of histogenesis

AIMS AND BACKGROUND

Various histogenetic mechanisms have been postulated to explain the biphasic carcinomatous-sarcomatous appearance of malignant mixed mullerian tumors (MMMTs), but the nature of these uncommon neoplasms is still unclear. Some evidence would suggest that MMMT displays similarities with sarcomatoid carcinoma, a tumor arising in extragenital sites that also features a mixed appearance. To gain further insight into the histogenesis of this tumor, we have studied by immunohistochemistry a case of uterine MMMT showing an extensive rhabdomyosarcomatous component.

METHODS

A panel of antibodies including reactivity for p53, cytokeratin, vimentin, desmin, muscle actin, epithelial membrane antigen (EMA), myoglobin, type IV collagen, laminin, and tenascin was applied to paraffin tumor sections by means of the avidin-biotin complex technique.

RESULTS

p53 immunoreactivity was observed in approximately the same number of cells in carcinomatous and sarcomatous tissue. The former stained for vimentin, cytokeratin and EMA, while the latter, in addition to expressing vimentin, desmin, muscle actin and myoglobin, also exhibited immunoreactivity for epithelial markers such as cytokeratin and EMA. At the borders between carcinoma and sarcoma the basement membrane pattern, as seen by staining for type IV collagen and laminin, showed interruptions in correspondence with areas of transition between the two tissues. Antibody to tenascin strongly labeled the sarcomatous tissue immediately around carcinomatous elements.

CONCLUSIONS

A similar immunoreactivity for p53 in both carcinomatous and sarcomatous components, expression of epithelial markers in the sarcomatous cells, and disruption of the basement membrane profile in areas of transition between carcinomatous and sarcomatous tissue, would all suggest, as has been postulated for extragenital sarcomatoid carcinomas, an origin from a common epithelial clone and an epithelial-to-mesenchymal transformation-based mechanism of development for this MMMT. In addition, these findings provide further analogies between these categories of tumors, supporting a unifying nosological concept for MMMTs and sarcomatoid carcinomas of non-genital tract origin.