Publications by authors named "Shubhada Shenai"

21 Publications

  • Page 1 of 1

Host blood RNA signatures predict the outcome of tuberculosis treatment.

Tuberculosis (Edinb) 2017 12 12;107:48-58. Epub 2017 Aug 12.

The Center for Infectious Disease Research, Seattle, WA, USA. Electronic address:

Biomarkers for tuberculosis treatment outcome will assist in guiding individualized treatment and evaluation of new therapies. To identify candidate biomarkers, RNA sequencing of whole blood from a well-characterized TB treatment cohort was performed. Application of a validated transcriptional correlate of risk for TB revealed symmetry in host gene expression during progression from latent TB infection to active TB disease and resolution of disease during treatment, including return to control levels after drug therapy. The symmetry was also seen in a TB disease signature, constructed from the TB treatment cohort, that also functioned as a strong correlate of risk. Both signatures identified patients at risk of treatment failure 1-4 weeks after start of therapy. Further mining of the transcriptomes revealed an association between treatment failure and suppressed expression of mitochondrial genes before treatment initiation, leading to development of a novel baseline (pre-treatment) signature of treatment failure. These novel host responses to TB treatment were integrated into a five-gene real-time PCR-based signature that captures the clinically relevant responses to TB treatment and provides a convenient platform for stratifying patients according to their risk of treatment failure. Furthermore, this 5-gene signature is shown to correlate with the pulmonary inflammatory state (as measured by PET-CT) and can complement sputum-based Gene Xpert for patient stratification, providing a rapid and accurate alternative to current methods.
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http://dx.doi.org/10.1016/j.tube.2017.08.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5658513PMC
December 2017

The New Xpert MTB/RIF Ultra: Improving Detection of and Resistance to Rifampin in an Assay Suitable for Point-of-Care Testing.

mBio 2017 08 29;8(4). Epub 2017 Aug 29.

Department of Medicine, Rutgers New Jersey Medical School, Newark, New Jersey, USA

The Xpert MTB/RIF assay (Xpert) is a rapid test for tuberculosis (TB) and rifampin resistance (RIF-R) suitable for point-of-care testing. However, it has decreased sensitivity in smear-negative sputum, and false identification of RIF-R occasionally occurs. We developed the Xpert MTB/RIF Ultra assay (Ultra) to improve performance. Ultra and Xpert limits of detection (LOD), dynamic ranges, and RIF-R mutation detection were tested on DNA or sputum samples spiked with known numbers of H37Rv or BCG CFU. Frozen and prospectively collected clinical samples from patients suspected of having TB, with and without culture-confirmed TB, were also tested. For H37Rv, the LOD was 15.6 CFU/ml of sputum for Ultra versus 112.6 CFU/ml of sputum for Xpert, and for BCG, it was 143.4 CFU/ml of sputum for Ultra versus 344 CFU/ml of sputum for Xpert. Ultra resulted in no false-positive RIF-R specimens, while Xpert resulted in two false-positive RIF-R specimens. All RIF-R-associated mutations tested were identified by Ultra. Testing on clinical sputum samples, Ultra versus Xpert, resulted in an overall sensitivity of 87.5% (95% confidence interval [CI], 82.1, 91.7) versus 81.0% (95% CI, 74.9, 86.2) and a sensitivity on sputum smear-negative samples of 78.9% (95% CI, 70.0, 86.1) versus 66.1% (95% CI, 56.4, 74.9). Both tests had a specificity of 98.7% (95% CI, 93.0, 100), and both had comparable accuracies for detection of RIF-R in these samples. Ultra should significantly improve TB detection, especially in patients with paucibacillary disease, and may provide more-reliable RIF-R detection. The Xpert MTB/RIF assay (Xpert), the first point-of-care assay for tuberculosis (TB), was endorsed by the World Health Organization in December 2010. Since then, 23 million Xpert tests have been procured in 130 countries. Although Xpert showed high overall sensitivity and specificity with pulmonary samples, its sensitivity has been lower with smear-negative pulmonary samples and extrapulmonary samples. In addition, the prediction of rifampin resistance (RIF-R) in paucibacillary samples and for a few mutations has resulted in both false-positive and false-negative results. The present study is the first demonstration of the design features and operational characteristics of an improved Xpert Ultra assay. This study also shows that the Ultra format overcomes many of the known shortcomings of Xpert. The new assay should significantly improve TB detection, especially in patients with paucibacillary disease, and provide more-reliable detection of RIF-R.
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http://dx.doi.org/10.1128/mBio.00812-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574709PMC
August 2017

Detection of Isoniazid-, Fluoroquinolone-, Amikacin-, and Kanamycin-Resistant Tuberculosis in an Automated, Multiplexed 10-Color Assay Suitable for Point-of-Care Use.

J Clin Microbiol 2017 01 28;55(1):183-198. Epub 2016 Dec 28.

Department of Medicine, New Jersey Medical School, Newark, New Jersey, USA.

Extensively drug-resistant (XDR) tuberculosis (TB) cannot be easily or quickly diagnosed. We developed a rapid, automated assay for the detection of XDR-TB plus resistance to the drug isoniazid (INH) for point-of-care use. Using a simple filter-based cartridge with an integrated sample processing function, the assay identified a wide selection of wild-type and mutant sequences associated with XDR-TB directly from sputum. Four new large-Stokes-shift fluorophores were developed. When these four Stokes-shift fluorophores were combined with six conventional fluorophores, 10-color probe detection in a single PCR tube was enabled. A new three-phase, double-nested PCR approach allowed robust melting temperature analysis with enhanced limits of detection (LODs). Finally, newly designed sloppy molecular beacons identified many different mutations using a small number of probes. The assay correctly distinguished wild-type sequences from 32 commonly occurring mutant sequences tested in gyrA, gyrB, katG, and rrs genes and the promoters of inhA and eis genes responsible for resistance to INH, the fluoroquinolone (FQ) drugs, amikacin (AMK), and kanamycin (KAN). The LOD was 300 CFU of Mycobacterium tuberculosis in 1 ml sputum. The rate of detection of heteroresistance by the assay was equivalent to that by Sanger sequencing. In a blind study of 24 clinical sputum samples, resistance mutations were detected in all targets with 100% sensitivity, with the specificity being 93.7 to 100%. Compared to the results of phenotypic susceptibility testing, the sensitivity of the assay was 75% for FQs and 100% each for INH, AMK, and KAN and the specificity was 100% for INH and FQ and 94% for AMK and KAN. Our approach could enable testing for XDR-TB in point-of-care settings, potentially identifying highly drug-resistant TB more quickly and simply than currently available methods.
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http://dx.doi.org/10.1128/JCM.01771-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5228229PMC
January 2017

Persisting positron emission tomography lesion activity and Mycobacterium tuberculosis mRNA after tuberculosis cure.

Nat Med 2016 10 5;22(10):1094-1100. Epub 2016 Sep 5.

National Medical Center, Seoul, South Korea.

The absence of a gold standard to determine when antibiotics induce a sterilizing cure has confounded the development of new approaches to treat pulmonary tuberculosis (PTB). We detected positron emission tomography and computerized tomography (PET-CT) imaging response patterns consistent with active disease, along with the presence of Mycobacterium tuberculosis (MTB) mRNA in sputum and bronchoalveolar lavage samples, in a substantial proportion of adult, HIV-negative patients with PTB after a standard 6-month treatment plus 1 year follow-up, including patients with a durable cure and others who later developed recurrent disease. The presence of MTB mRNA in the context of nonresolving and intensifying lesions on PET-CT images might indicate ongoing transcription, suggesting that even apparently curative treatment for PTB may not eradicate all of the MTB bacteria in most patients. This suggests an important complementary role for the immune response in maintaining a disease-free state. Sterilizing drugs or host-directed therapies, and better treatment response markers, are probably needed for the successful development of improved and shortened PTB-treatment strategies.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5053881PMC
http://dx.doi.org/10.1038/nm.4177DOI Listing
October 2016

Bacterial Loads Measured by the Xpert MTB/RIF Assay as Markers of Culture Conversion and Bacteriological Cure in Pulmonary TB.

PLoS One 2016 10;11(8):e0160062. Epub 2016 Aug 10.

Division of Infectious Diseases, Rutgers New Jersey Medical School, ^Rutgers Biomedical & Health Sciences (Formerly UMDNJ), 185 South Orange Avenue, Newark, New Jersey, United States of America.

Introduction: Biomarkers are needed to monitor tuberculosis (TB) treatment and predict treatment outcomes. We evaluated the Xpert MTB/RIF (Xpert) assay as a biomarker for TB treatment during and at the end of the 24 weeks therapy.

Methods: Sputum from 108 HIV-negative, culture-positive pulmonary TB patients was analyzed using Xpert at time points before and during anti-TB therapy. Results were compared against culture. Direct Xpert cycle-threshold (Ct), a change in the Ct (delta Ct), or a novel "percent closing of baseline Ct deficit" (percent closing) were evaluated as classifiers of same-day and end-of-treatment culture and therapeutic outcomes.

Results: Xpert was positive in 29/95 (30.5%) of subjects at week 24; and positive one year after treatment in 8/64 (12.5%) successfully-treated patients who remained free of tuberculosis. We identified a relationship between initial bacterial load measured by baseline Xpert Ct and time to culture conversion (hazard ratio 1.06, p = 0.0023), and to the likelihood of being among the 8 treatment failures at week 24 (AUC = 72.8%). Xpert Ct was even more strongly associated with culture conversion on the day the test was performed with AUCs 96.7%, 99.2%, 86.0% and 90.2%, at Day 7, Week 4, 8 and 24, respectively. Compared to baseline Ct measures alone, a combined measure of baseline Ct plus either Delta Ct or percent closing improved the classification of treatment failure status to a 75% sensitivity and 88.9% specificity.

Conclusions: Genome loads measured by Xpert provide a potentially-useful biomarker for classifying same day culture status and predicting response to therapy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0160062PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980126PMC
August 2017

Analytical and Clinical Evaluation of the Epistem Genedrive Assay for Detection of Mycobacterium tuberculosis.

J Clin Microbiol 2016 Apr 10;54(4):1051-7. Epub 2016 Feb 10.

Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

The Epistem Genedrive assay rapidly detects the Mycobacterium tuberculosis omplex from sputum and is currently available for clinical use. However, the analytical and clinical performance of this test has not been fully evaluated. The analytical limit of detection (LOD) of the Genedrive PCR amplification was tested with genomic DNA; the performance of the complete (sample processing plus amplification) system was tested by spiking M. tuberculosismc(2)6030 cells into distilled water andM. tuberculosis-negative sputum. Specificity was tested using common respiratory pathogens and nontuberculosis mycobacteria. A clinical evaluation enrolled adults with suspected pulmonary tuberculosis, obtained three sputum samples from each participant, and compared the accuracy of the Gene drive to that of the Xpert MTB/RIF assay using M. tuberculosiscultures as the reference standard. The Genedrive assay had an LOD of 1 pg/μl (100 genomic DNA copies/reaction). The LODs of the system were 2.5 × 10(4)CFU/ml and 2.5 × 10(5)CFU/ml for cells spiked into water and sputum, respectively. False-positiverpoBprobe signals were observed in 3/32 (9.4%) of the negative controls and also in few samples containing Mycobacterium abscessus,Mycobacterium gordonae, o rMycobacterium thermoresistibile In the clinical study, among 336 analyzed participants, the overall sensitivities for the tuberculosis case detection of Gene drive, Xpert, and smear microscopy were 45.4% (95% confidence interval [CI], 35.2% to 55.8%), 91.8% (95% CI, 84.4% to 96.4%), and 77.3% (95% CI, 67.7% to 85.2%), respectively. The sensitivities of Gene drive and Xpert for the detection of smear-microscopy-negative tuberculosis were 0% (95% CI, 0% to 15.4%) and 68.2% (95% CI, 45.1% to 86.1%), respectively. The Genedrive assay did not meet performance standards recommended by the World Health Organization for a smear microscopy replacement tuberculosis test. Epistem is working on modifications to improve the assay.
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http://dx.doi.org/10.1128/JCM.02847-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4809910PMC
April 2016

Phosphorylation of KasB regulates virulence and acid-fastness in Mycobacterium tuberculosis.

PLoS Pathog 2014 May 8;10(5):e1004115. Epub 2014 May 8.

Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS; UMR 5235, Montpellier, France; INSERM, DIMNP, Montpellier, France.

Mycobacterium tuberculosis bacilli display two signature features: acid-fast staining and the capacity to induce long-term latent infections in humans. However, the mechanisms governing these two important processes remain largely unknown. Ser/Thr phosphorylation has recently emerged as an important regulatory mechanism allowing mycobacteria to adapt their cell wall structure/composition in response to their environment. Herein, we evaluated whether phosphorylation of KasB, a crucial mycolic acid biosynthetic enzyme, could modulate acid-fast staining and virulence. Tandem mass spectrometry and site-directed mutagenesis revealed that phosphorylation of KasB occurred at Thr334 and Thr336 both in vitro and in mycobacteria. Isogenic strains of M. tuberculosis with either a deletion of the kasB gene or a kasB_T334D/T336D allele, mimicking constitutive phosphorylation of KasB, were constructed by specialized linkage transduction. Biochemical and structural analyses comparing these mutants to the parental strain revealed that both mutant strains had mycolic acids that were shortened by 4-6 carbon atoms and lacked trans-cyclopropanation. Together, these results suggested that in M. tuberculosis, phosphorylation profoundly decreases the condensing activity of KasB. Structural/modeling analyses reveal that Thr334 and Thr336 are located in the vicinity of the catalytic triad, which indicates that phosphorylation of these amino acids would result in loss of enzyme activity. Importantly, the kasB_T334D/T336D phosphomimetic and deletion alleles, in contrast to the kasB_T334A/T336A phosphoablative allele, completely lost acid-fast staining. Moreover, assessing the virulence of these strains indicated that the KasB phosphomimetic mutant was attenuated in both immunodeficient and immunocompetent mice following aerosol infection. This attenuation was characterized by the absence of lung pathology. Overall, these results highlight for the first time the role of Ser/Thr kinase-dependent KasB phosphorylation in regulating the later stages of mycolic acid elongation, with important consequences in terms of acid-fast staining and pathogenicity.
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http://dx.doi.org/10.1371/journal.ppat.1004115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4014462PMC
May 2014

Exploring alternative biomaterials for diagnosis of pulmonary tuberculosis in HIV-negative patients by use of the GeneXpert MTB/RIF assay.

J Clin Microbiol 2013 Dec 9;51(12):4161-6. Epub 2013 Oct 9.

Center for Infectious Diseases, New Jersey Medical School, Rutgers Biomedical & Health Sciences (formerly UMDNJ), Newark, New Jersey, USA.

The utility of the GeneXpert MTB/RIF (Xpert) assay for detection of Mycobacterium tuberculosis in sputum samples has been extensively studied. However, the performance of the Xpert assay as applied to other readily accessible body fluids such as exhaled breath condensate (EBC), saliva, urine, and blood has not been established. We used the Xpert assay to test EBC, saliva, urine, and blood samples from HIV-negative, smear- and culture-positive pulmonary tuberculosis (TB) patients for the presence of M. tuberculosis. To compare the ability of the assay to perform bacterial load measurements on sputum samples with versus without sample processing, the assay was also performed on paired direct and processed sputum samples from each patient. The Xpert assay detected M. tuberculosis in none of the 26 EBC samples (sensitivity, 0.0%; 95% confidence interval [95% CI], 0.0%, 12.9%), 10 of the 26 saliva samples (sensitivity, 38.5%; 95% CI, 22.4%, 57.5%), 1 of 26 urine samples (sensitivity, 3.8%; 95% CI, 0.7%, 18.9%), and 2 of 24 blood samples (sensitivity, 8.3%; 95% CI, 2.3%, 25.8%). For bacterial load measurements in the different types of sputum samples, the cycle thresholds of the two M. tuberculosis-positive sputum types were well correlated (Spearman correlation of 0.834). This study demonstrates that the Xpert assay should not be routinely used to detect M. tuberculosis in EBC, saliva, urine, or blood samples from HIV-negative patients suspected of having pulmonary tuberculosis. As a test of bacterial load, the assay produced similar results when used to test direct versus processed sputum samples. Sputum remains the optimal sample type for diagnosing pulmonary tuberculosis in HIV-negative patients with the Xpert assay.
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http://dx.doi.org/10.1128/JCM.01743-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3838083PMC
December 2013

Antituberculosis thiophenes define a requirement for Pks13 in mycolic acid biosynthesis.

Nat Chem Biol 2013 Aug 16;9(8):499-506. Epub 2013 Jun 16.

Division of Infectious Disease, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA.

We report a new class of thiophene (TP) compounds that kill Mycobacterium tuberculosis by the previously uncharacterized mechanism of Pks13 inhibition. An F79S mutation near the catalytic Ser55 site in Pks13 conferred TP resistance in M. tuberculosis. Overexpression of wild-type Pks13 resulted in TP resistance, and overexpression of the Pks13(F79S) mutant conferred high resistance. In vitro, TP inhibited fatty acyl-AMP loading onto Pks13. TP inhibited mycolic acid biosynthesis in wild-type M. tuberculosis, but it did so to a much lesser extent in TP-resistant M. tuberculosis. TP treatment was bactericidal and equivalent to treatment with the first-line drug isoniazid, but it was less likely to permit emergent resistance. Combined isoniazid and TP treatment resulted in sterilizing activity. Computational docking identified a possible TP-binding groove within the Pks13 acyl carrier protein domain. This study confirms that M. tuberculosis Pks13 is required for mycolic acid biosynthesis, validates it as a druggable target and demonstrates the therapeutic potential of simultaneously inhibiting multiple targets in the same biosynthetic pathway.
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http://dx.doi.org/10.1038/nchembio.1277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3720791PMC
August 2013

Fading of auramine-stained mycobacterial smears and implications for external quality assurance.

J Clin Microbiol 2011 May 23;49(5):2024-6. Epub 2011 Mar 23.

Department of Epidemiology, McGill University, Montreal, Canada.

Light-emitting diode fluorescence microscopy is being scaled up for tuberculosis control, but fading of auramine-stained slides could compromise external quality assurance. We stored auramine-stained slides and reexamined them over time. Slides stored in all environments faded quickly, with significant changes in the proportion of positive slides in as little as 1 week.
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http://dx.doi.org/10.1128/JCM.00507-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3122634PMC
May 2011

Mutation detection and accurate diagnosis of extensively drug-resistant tuberculosis: report from a tertiary care center in India.

J Clin Microbiol 2011 Apr 2;49(4):1588-90. Epub 2011 Feb 2.

Department of Research, P. D. Hinduja National Hospital and Medical Research Centre, Veer Savarkar Marg, Mahim, Mumbai 400016, India.

We screened and spoligotyped 150 consecutive phenotypically confirmed extensively drug-resistant Mycobacterium tuberculosis (XDR-TB) isolates (January 2008 to March 2009) for rifampin, isoniazid, fluoroquinolone, and aminoglycoside resistance targeting rpoB, inhA, katG, gyrA, gyrB, and rrs. Mutations predominant among XDR-TB were S315T (katG) (100% of isolates), S531L (rpoB) (97% of isolates), D94G (gyrA) (53% of isolates), and A1401G (rrs) (71% of isolates). Spoligotyping revealed 62% of the isolates to be Beijing.
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http://dx.doi.org/10.1128/JCM.00113-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3122820PMC
April 2011

Comparison of Mycobacterium tuberculosis culture using liquid culture medium and Lowenstein Jensen medium in abdominal tuberculosis.

Indian J Gastroenterol 2010 Nov 11;29(6):237-9. Epub 2011 Jan 11.

Division of GI Surgery, P D Hinduja Hospital and Medical Research Centre, Mumbai 400 016, India.

Background: Traditionally, the Lowenstein Jensen (LJ) medium has been used for culturing Mycobacterium tuberculosis. In abdominal tuberculosis (TB), the reported yield from tissue culture is between 20% and 60%. Liquid cultures are reported to give a higher yield but there is little data available in abdominal TB.

Aim: To compare the yield of TB culture with BACTEC 460TB liquid medium and LJ medium for patients with suspected abdominal TB and determine cost effectiveness.

Methods: This prospective study was done in consecutive cases with clinical, radiological, endoscopic/surgical, and histological suspicion of abdominal TB. Tissue biopsies obtained at colonoscopy or surgery were processed and plated on LJ medium as well as the BACTEC 460TB system. NAP (ρ-nitro-α-acetylamino-β-hydroxy-propiophenone) differentiation was carried out to determine species. The cost of each method and cost per yield were calculated.

Results: Of the 29 cases, 22 cases (76%) were positive on BACTEC 460TB culture while 14 (48%) were positive on LJ medium giving a 64% increment in yield. However, the culture of one patient grew on LJ medium, where the BACTEC 460TB was negative. The additional cost of BACTEC 460TB is Rs. 460 and LJ is Rs. 40.

Conclusions: Samples from patients with abdominal TB should be processed on both liquid and LJ medium. For high yield, the use of a liquid culture medium system is essential.
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http://dx.doi.org/10.1007/s12664-010-0075-3DOI Listing
November 2010

Can cord formation in BACTEC MGIT 960 medium be used as a presumptive method for identification of M. tuberculosis complex?

Indian J Tuberc 2010 Apr;57(2):75-9

P.D. Hinduja National Hospital & Medical Research Centre, Mahim, Mumbai

Background: Serpentine cord formation in BACTEC MGIT 960 medium was evaluated as a rapid method for the presumptive identification of M. tuberculosis complex (MTBC).

Material & Methods: Total 2527 samples were processed for AFB culture using MGIT 960 TB system over a period of three months. AFB smears were prepared from 1000 MGIT tubes flagged positive by the MGIT instrument and stained by ZN method to examine presence or absence of serpentine cording. The cord formation was compared with PNBA [p-nitro benzoic acid] test on MGIT system and all controversial cases were further evaluated by NAP [p-nitro-a-acetylamino-phydroxypropiophenone] test on BACTEC 460 TB system.

Results & Discussion: Of the 1000 culture positives, 904 (90.4%) were identified as mycobacteria, of which 869 (96%) showed cording by smear microscopy. One (0.1%) was identified as nocardia. In the remaining 95 (9.5%) cases, primary smear made from MGIT vial was negative. Of 869 cultures showing serpentine cord formation, 842 were confirmed as MTBC and 27 as NTM by PNBA assay on MGIT 960 TB system. The sensitivity, specificity, positive and negative predictive values are found to be 99.6%, 54%, 96% and 91% respectively. An average detection time for PNBA assay was found to be eight days whereas cording results were available on the same day of culture positivity.

Conclusion: Though highly sensitive it is not very specific and hence cannot be the only test for presumptive diagnosis of MTBC.
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April 2010

Rapid molecular detection of tuberculosis and rifampin resistance.

N Engl J Med 2010 Sep 1;363(11):1005-15. Epub 2010 Sep 1.

Foundation for Innovative New Diagnostics, Geneva, Switzerland.

Background: Global control of tuberculosis is hampered by slow, insensitive diagnostic methods, particularly for the detection of drug-resistant forms and in patients with human immunodeficiency virus infection. Early detection is essential to reduce the death rate and interrupt transmission, but the complexity and infrastructure needs of sensitive methods limit their accessibility and effect.

Methods: We assessed the performance of Xpert MTB/RIF, an automated molecular test for Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF), with fully integrated sample processing in 1730 patients with suspected drug-sensitive or multidrug-resistant pulmonary tuberculosis. Eligible patients in Peru, Azerbaijan, South Africa, and India provided three sputum specimens each. Two specimens were processed with N-acetyl-L-cysteine and sodium hydroxide before microscopy, solid and liquid culture, and the MTB/RIF test, and one specimen was used for direct testing with microscopy and the MTB/RIF test.

Results: Among culture-positive patients, a single, direct MTB/RIF test identified 551 of 561 patients with smear-positive tuberculosis (98.2%) and 124 of 171 with smear-negative tuberculosis (72.5%). The test was specific in 604 of 609 patients without tuberculosis (99.2%). Among patients with smear-negative, culture-positive tuberculosis, the addition of a second MTB/RIF test increased sensitivity by 12.6 percentage points and a third by 5.1 percentage points, to a total of 90.2%. As compared with phenotypic drug-susceptibility testing, MTB/RIF testing correctly identified 200 of 205 patients (97.6%) with rifampin-resistant bacteria and 504 of 514 (98.1%) with rifampin-sensitive bacteria. Sequencing resolved all but two cases in favor of the MTB/RIF assay.

Conclusions: The MTB/RIF test provided sensitive detection of tuberculosis and rifampin resistance directly from untreated sputum in less than 2 hours with minimal hands-on time. (Funded by the Foundation for Innovative New Diagnostics.)
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http://dx.doi.org/10.1056/NEJMoa0907847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947799PMC
September 2010

Comparison of phenotypic and genotypic methods for pyrazinamide susceptibility testing.

Indian J Tuberc 2009 Apr;56(2):82-90

P.D. Hinduja National Hospital and Medical Research Centre. Mahim, Mumbai-16.

Objectives: To evaluate Pyrazinamide (PZA) susceptibility results obtained by phenotypic MGIT 960 TB system against enzymatic Pyrazinamidase assay and genotypic pncA gene sequencing. To find the prevalence of infections caused by M. bovis in PZA resistant M. tuberculosis complex isolates.

Methods: 33 consecutive PZA resistant and 30 consecutive PZA susceptible isolates reported for PZA susceptibility testing by MGIT 960 TB system were included in this study. Presence of active pyrazinamidase enzyme was sought by using the Wayne assay. The pncA gene was amplified by PCR and then sequenced to screen mutations. All the PZA resistant isolates were further spoligotyped to identify M. bovis, if present.

Results: Of 33 PZA resistant strains by MGIT 960, 31 were Wayne assay negative and two were positive. Of the 30 susceptible PZA strains six were Wayne assay negative reporting false resistance. PncA gene sequencing revealed that 32 of the 33 MGIT PZA resistant isolates had diverse nucleotide changes scattered throughout the pncA gene (one isolate did not show any mutation). Of the 30 phenotypically susceptible isolates, 21 were wild types whilst nine isolates showed the presence of a silent mutation C-T at codon 195. Fifteen mutations found in this study has not been described earlier. Not a single isolate of M. bovis was detected among PZA resistant M. tuberculosis complex isolates.

Conclusion: MGIT 960 showed better concordance with sequencing results in comparison with Wayne assay. In present study, a high proportion (85%) of MDR-TB isolates from patients receiving anti-TB treatment were found to be resistant to PZA.
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April 2009

Osteoarticular tuberculosis--diagnostic solutions in a disease endemic region.

J Infect Dev Ctries 2009 Aug 30;3(7):511-6. Epub 2009 Aug 30.

P.D. Hinduja National Hospital & Medical Research Centre, Mahim, Mumbai-400016, India.

Background: We conducted a study of osteoarticular tuberculosis in patients from private and public settings in a disease endemic area. Our objective was to assess the role of mycobacterial culture and polymerase chain reaction (PCR) in the diagnosis of osteoarticular tuberculosis (TB) in settings where only clinical and imaging diagnosis form the basis for treatment.

Methodology: Ninety-three consecutive specimens collected from clinically suspected patients of osteoarticular TB were screened for bacterial culture, mycobacterial culture and in-house nested PCR. In addition, specimens were examined by imaging and histopathology. Ten specimens collected from patients suffering from other bone diseases were included as negative controls.

Results: Of the 93 clinically suspected TB patients, mycobacterial culture was positive for Mycobacterium tuberculosis (MTB) in 47 (51%) patients who were confirmed as definite TB cases. Of the remaining patients, 16 (17%) were diagnosed as probable, 19 (20%) as possible, and 11 (12%) as only clinically suspected TB cases. In-house nested PCR was positive in 65 (70%) cases. Fifteen patients were resistant to one or more anti-tuberculous drugs; twelve patients were multi-drug resistant, two of whom were extensively drug resistant.

Conclusion: Mycobacterial cultures using liquid media with susceptibility should form the backbone of management of osteoarticular TB. Nested PCR enhances the sensitivity if performed in addition to culture.
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http://dx.doi.org/10.3855/jidc.469DOI Listing
August 2009

Rapid speciation of 15 clinically relevant mycobacteria with simultaneous detection of resistance to rifampin, isoniazid, and streptomycin in Mycobacterium tuberculosis complex.

Int J Infect Dis 2009 Jan 18;13(1):46-58. Epub 2008 Jun 18.

P.D. Hinduja National Hospital and Medical Research Centre, Maharashtra, India.

Objective: To design and standardize an in-house reverse line blot hybridization (RLBH) assay for the accurate identification of 15 clinically relevant species of mycobacteria and for the detection of drug resistance to rifampin (RIF), isoniazid (INH), and streptomycin (STR) in Mycobacterium tuberculosis complex (MTB).

Material And Methods: Oligonucleotides specific for 15 different species of mycobacteria and wild type and mutant alleles of selected codons in the rpobeta, inhA, katG, rpsL, and rrs genes were designed and immobilized on a membrane. A multiplex PCR was standardized to amplify all target genes. The assay was optimized using ATCC and known mutant strains. Three hundred MTB isolates, 85 non-tuberculous mycobacteria (NTM) isolates, and 48 smear-positive specimens were analyzed. Results were confirmed by PCR restriction enzyme assay and sequencing.

Results: Upon RLBH analysis, among the NTM, 14% were identified as Mycobacterium fortuitum, 16% were identified as Mycobacterium abscessus, 20% showed 99% homology with Mycobacterium intracellulare, and 31% showed 98% homology with Mycobacterium simiae. Of the 300 MTB isolates analyzed, 75% RIF-resistant isolates had Ser531Leu mutation in the rpobeta gene. Of the INH-resistant isolates, 89% showed Ser315Thr mutation in the katG gene, whereas 16% showed -15 C-->T mutation in the promoter region of the inhA gene. Among STR-resistant isolates, 75% had A-->G mutation in the rpsL gene at codon 43. RLBH results showed 96-99% concordance with phenotypic culture results.

Conclusion: This is a first attempt at combining speciation with detection of drug resistance to RIF, INH, and STR in MTB for accurate and rapid management of mycobacterial infections as well as for compiling genotypic epidemiological data.
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http://dx.doi.org/10.1016/j.ijid.2008.03.025DOI Listing
January 2009
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