Rupak Singla

Linezolid: an effective, safe and cheap drug for patients failing multidrug-resistant tuberculosis treatment in India

Linezolid is identified as an effective drug with which to treat patients failing multidrug-resistant (MDR)-tuberculosis (TB) treatment. However, cost and safety are the concerns. In India, the average price of a 600-mg pill of linezolid is less than one US dollar, much cheaper than most of the third-line drugs. A prospective study of 29 MDR-TB treatment failure patients (16 with laboratory-proven extensively drug-resistant (XDR)-TB and the remaining 13 with MDR-TB with resistance to any quinolone but sensitive to injectables) was carried out in Delhi, India. All patients received daily unsupervised therapy with linezolid, one injectable agent, one fluoroquinolone and two or more other drugs. Patients received a median of six anti-mycobacterial agents. Besides linezolid, capreomycin, moxifloxacin, levofloxacin and amoxycillin-clavulanic acid were used in 41.4%, 58.6%, 41.4%, and 79.3% of patients. Out of a total of 29 patients, 89.7% patients achieved sputum smear and culture conversion; 72.4% showed interim favourable outcome; 10.3% died, 6.8% failed and 10.3% patients defaulted. Linezolid had to be stopped in three (10.3%) patients due to adverse reactions. The outcome of treatment of 16 XDR-TB patients was comparable to the other 13 MDR-TB patients. Linezolid is an effective, cheap and relatively safe drug for patients failing MDR-TB treatment, including those with confirmed XDR-TB.

Voltage Gated Calcium Channels Negatively Regulate Protective Immunity to Mycobacterium tuberculosis

Mycobacterium tuberculosis modulates levels and activity of key intracellular second messengers to evade protective immune responses. Calcium release from voltage gated calcium channels (VGCC) regulates immune responses to pathogens. In this study, we investigated the roles of VGCC in regulating protective immunity to mycobacteria in vitro and in vivo. Inhibiting L-type or R-type VGCC in dendritic cells (DCs) either using antibodies or by siRNA increased calcium influx in an inositol 1,4,5-phosphate and calcium release calcium activated channel dependent mechanism that resulted in increased expression of genes favoring pro-inflammatory responses. Further, VGCC-blocked DCs activated T cells that in turn mediated killing of M. tuberculosis inside macrophages. Likewise, inhibiting VGCC in infected macrophages and PBMCs induced calcium influx, upregulated the expression of pro-inflammatory genes and resulted in enhanced killing of intracellular M. tuberculosis. Importantly, compared to healthy controls, PBMCs of tuberculosis patients expressed higher levels of both VGCC, which were significantly reduced following chemotherapy. Finally, blocking VGCC in vivo in M. tuberculosis infected mice using specific antibodies increased intracellular calcium and significantly reduced bacterial loads. These results indicate that L-type and R-type VGCC play a negative role in M. tuberculosis infection by regulating calcium mobilization in cells that determine protective immunity.

Toll-like Receptor 2 and DC-SIGNR1 Differentially Regulate Suppressors of Cytokine Signaling 1 in Dendritic Cells during Mycobacterium tuberculosis Infection

A hallmark of protective immunity during Mycobacterium tuberculosis (M. tb) infection is the regulated secretion of pro-inflammatory and regulatory cytokines. Suppressors of Cytokine Signaling (SOCS) are key regulators of cytokine secretion and function. In this study we investigated regulation of Toll-like receptor 2 (TLR2) and dendritic cell-specific ICAM-3 grabbing non-integrin receptor 1 (DC-SIGNR1)-mediated SOCS1 expression in DCs during M. tb infection. We show that, compared with TLR2, stimulating DC-SIGNR1 on DCs induces higher SOCS1 expression and lower interleukin-12 production. Co-stimulating DC-SIGNR1 and TLR2 differentially regulates SOCS1 expression depending on the relative concentration of their ligands. Stimulating DC-SIGNR1 with M. tb infection increases SOCS1 expression, while stimulating TLR2 with M. tb infection reduces SOCS1 expression. Knockdown of SOCS1 in DCs by siRNA enhances interleukin-12 transcription and protein expression upon DC-SIGNR1 stimulation. Raf-1 and Syk differentially regulate TLR2- and DC-SIGNR1-mediated SOCS1 expression. In addition, DC-SIGNR1 shows greater association with SOCS1 when compared with TLR2. Interestingly, compared with healthy asymptomatic individuals, peripheral blood mononuclear cells of patients with active tuberculosis disease showed higher expression of SOCS1, which was reduced following chemotherapy. Similarly, stimulating DC-SIGNR1 on DCs from M. tb-infected TLR2−/− mice enhanced SOCS1 expression that was reduced following chemotherapy. Further, knockdown of SOCS1 in mouse DCs or human peripheral blood mononuclear cells resulted in increased killing of virulent M. tb. These results indicate that TLR2 and DC-SIGNR1 differentially regulate SOCS1 expression during M. tb infection. This in turn regulates M. tb survival by governing key cytokine expression.

Incidence and Risk Factors for Extensively Drug-Resistant Tuberculosis in Delhi Region

Background India with a major burden of multidrug-resistant tuberculosis (MDR-TB) does not have national level data on this hazardous disease. Since 2006, emergence of extensively drug-resistant TB (XDR-TB) is considered a serious threat to global TB control. This study highlights the demographic and clinical risk factors associated with XDR-TB in Delhi. Methods The study was conducted during April 2007 to May 2010. Six hundred eleven MDR-TB suspects were enrolled from four tertiary care hospitals, treating TB patients in Delhi and the demographic details recorded. Sputum samples were cultured using rapid, automated liquid culture system (MGIT 960). Drug susceptibility testing (DST) for Rifampicin (RIF) and Isoniazid (INH) was performed for all positive M. tuberculosis (M.tb) cultures. All MDR-TB isolates were tested for sensitivity to second-line drugs [Amikacin (AMK), Capreomycin (CAP), Ofloxacin (OFX), Ethionamide (ETA)]. Results/Findings Of 611, 483 patients were infected with MDR M. tuberculosis (M.tb) strains. Eighteen MDR-TB isolates (3.7%) were XDR M.tb strains. Family history of TB (p 0.045), socioeconomic status (p 0.013), concomitant illness (p 0.001) and previous intake of 2nd line injectable drugs (p 0.001) were significantly associated with occurrence of XDR-TB. Only two of the patients enrolled were HIV seropositive, but had a negative culture for M. tuberculosis. 56/483 isolates were pre-XDR M. tuberculosis, though the occurrence of pre-XDR-TB did not show any significant demographical associations. Conclusions The actual incidence and prevalence rate of XDR-TB in India is not available, although some scattered data is available. This study raises a concern about existence of XDR-TB in India, though small, signaling a need to strengthen the TB control program for early diagnosis of both tuberculosis and drug resistance in order to break the chains of transmission.

Suppressors of cytokine signaling inhibit effector T cell responses during Mycobacterium tuberculosis Infection

Protective immune responses during Mycobacterium tuberculosis (M. tuberculosis) infection are regulated at multiple levels and critically dependent on the balance in the secretion of pro‐inflammatory and regulatory cytokines. A key factor that governs this balance at the cellular level is suppressors of cytokine signaling (SOCS). We recently demonstrated that toll‐like receptor 2 and dendritic cell (DC)‐SIGNR1 differentially regulate SOCS1 expression in DCs during M. tuberculosis infection. This consecutively regulated IL‐12 production and determined M. tuberculosis survival. In this study, we characterized the role of SOCS1 in regulating effector responses from CD4+ and CD8+ T cells during M. tuberculosis infection. Our data indicate that T cells from M. tuberculosis‐infected mice show increased and differential association of SOCS1 with CD3 and CD28, when compared with uninfected mice. While SOCS1 displays increased association with CD3 than CD28 in CD4+ T cells; SOCS1 is associated more with CD28 than CD3 in CD8+ T cells. Further, SOCS1 shows increased association with IL‐12 and IL‐2 receptors in both CD4+ and CD8+ T cells from infected mice when compared with naive mice. Silencing SOCS1 in T cells increased signal transduction from T cell receptor (TCR) and CD28 with enhanced activation of key signaling molecules and proliferation. Significantly, SOCS1‐silenced T cells mediated enhanced clearance of M. tuberculosis inside macrophages. Finally, adoptive transfer of SOCS1‐silenced T cells in M. tuberculosis‐infected mice mediated significant reduction in M. tuberculosis loads in spleen. These results exemplify the negative role played by SOCS1 during T cell priming and effector functions during M. tuberculosis infection.

Sputum smear positivity at two months in previously untreated pulmonary tuberculosis patients

BACKGROUND AND OBJECTIVES In pulmonary tuberculosis, bacteriological status at two months affects subsequent treatment and prognosis. The effect on treatment outcome and risk factors for sputum conversion at two months treatment in previously untreated pulmonary tuberculosis (PTB) patients was studied in the following report. METHODS A 1:1 case-control study was performed from June 2006 to February 2008 on patients in the Revised National Tuberculosis Control Program in a tertiary level institute in Delhi, India. Patients with previously untreated PTB with sputum smear positive at 2months of treatment (cases) were compared with those who achieved conversion (controls). RESULTS In 74 cases and 74 controls, independent risk factors for sputum smear positive at two months were: illness for >2months, presence of cavity or extensive disease on chest X-ray, and interruption in intensive phase of treatment. Patients with smear positive at 2 or 3months of treatment were more likely to fail or default from treatment. Aforesaid factors were also associated with sputum culture positive status at 2months in univariate analysis. Patients who interrupted treatment ⩾3 times in the first two months were more likely to be culture positive at two months and had a higher rate of default and failure. CONCLUSIONS Illness for more than 2months, presence of cavity or extensive disease on chest X-ray, and interruption in intensive phase of treatment are independent risk factors for sputum smear positivity at two months, which in turn is associated with poor treatment outcomes. Patients with these factors merit special attention under the national program.

Recurrence of tuberculosis among newly diagnosed sputum positive pulmonary tuberculosis patients treated under the Revised National Tuberculosis Control Programme, India: A multi-centric prospective study

Introduction There is lack of information on the proportion of new smear—positive pulmonary tuberculosis (PTB) patients treated with a 6-month thrice-weekly regimen under Revised National Tuberculosis Control Programme (RNTCP) who develop recurrent TB after successful treatment outcome. Objective To estimate TB recurrence among newly diagnosed PTB patients who have successfully completed treatment and to document endogenous reactivation or re-infection. Risk factors for unfavourable outcomes to treatment and TB recurrence were determined. Methodology Adult (aged ≥ 18 yrs) new smear positive PTB patients initiated on treatment under RNTCP were enrolled from sites in Tamil Nadu, Karnataka, Delhi, Maharashtra, Madhya Pradesh and Kerala. Those declared “treatment success” at the end of treatment were followed up with 2 sputum examinations each at 3, 6 and 12 months after treatment completion. MIRU-VNTR genotyping was done to identify endogenous re-activation or exogenous re-infection at TB recurrence. TB recurrence was expressed as rate per 100 person-years (with 95% confidence interval [95%CI]). Regression models were used to identify the risk factors for unfavourable response to treatment and TB recurrence. Results Of the1577 new smear positive PTB patients enrolled, 1565 were analysed. The overall cure rate was 77% (1207/1565) and treatment success was 77% (1210 /1565). The cure rate varied from 65% to 86%. There were 158 of 1210 patients who had TB recurrence after treatment success. The pooled TB recurrence estimate was 10.9% [95%CI: 0.2–21.6] and TB recurrence rate per 100 person–years was 12.7 [95% CI: 0.4–25]. TB recurrence per 100 person–years varied from 5.4 to 30.5. Endogenous reactivation was observed in 56 (93%) of 60 patients for whom genotyping was done. Male gender was associated with TB recurrence. Conclusion A substantial proportion of new smear positive PTB patients successfully treated with 6 –month thrice-weekly regimen have TB recurrence under program settings.

Tuberculosis preventive treatment: the next chapter of tuberculosis elimination in India

The End TB Strategy envisions a world free of tuberculosis—zero deaths, disease and suffering due to tuberculosis by 2035. This requires reducing the global tuberculosis incidence from >1250 cases per million people to <100 cases per million people within the next two decades. Expanding testing and treatment of tuberculosis infection is critical to achieving this goal. In high-burden countries, like India, the implementation of tuberculosis preventive treatment (TPT) remains a low priority. In this analysis article, we explore potential challenges and solutions of implementing TPT in India. The next chapter in tuberculosis elimination in India will require cost-effective and sustainable interventions aimed at tuberculosis infection. This will require constant innovation, locally driven solutions to address the diverse and dynamic tuberculosis epidemiology and persistent programme monitoring and evaluation. As new tools, regimens and approaches emerge, midcourse adjustments to policy and practice must be adopted. The development and implementation of new tools and strategies will call for close collaboration between local, national and international partners—both public and private—national health authorities, non-governmental organisations, research community and the diagnostic and pharmaceutical industry. Leading by example, India can contribute to global knowledge through operational research and programmatic implementation for combating tuberculosis infection.

Risk factors associated with development of pulmonary impairment after tuberculosis.

BACKGROUND Treatment of pulmonary tuberculosis (PTB) focuses on microbiological cure and radiological improvement. However, many patients develop pulmonary impairment after the completion of anti-tubercular therapy (ATT), which affects their quality of life (QoL). AIM AND OBJECTIVE To study the occurrence and severity of pulmonary impairment after tuberculosis (PIAT), risk factors associated with development of PIAT and QoL after development of PIAT. METHODOLOGY 146 eligible PTB patients, who completed their ATT during January 2013 to December 2013 at National Institute of TB and Respiratory Diseases (NITRD), New Delhi and peripheral centres were enrolled after informed consent and evaluated. PIAT was graded using spirometric parameters. Severity of dyspnoea was assessed using Borg scale and Medical Research Council (MRC) scale. QoL was assessed using Seattles Obstructive Lung Diseases Questionnaire (SOLDQ). RESULTS 74% (108) had PIAT. On univariate analysis, smoking, education, body mass index (BMI), duration of illness prior to diagnosis of TB and number of prior ATT courses taken were the significant risk factors associated with the development of PIAT. On multiple logistic regression, patients who had taken ATT more than once was the independent risk factor associated with PIAT. Severity of dyspnoea was increased on both Borg scale and MRC scale with the increase in impairment of lung function. QoL was lower in patients with severe impairment. CONCLUSION After bacteriological cure of TB after treatment, significant numbers of patients have poor lung function and poor QoL. There is need for prevention and management of such sequelae under national programme.

Linezolid: safety and efficacy monitoring

From the authors: We read with interest the comments by M.S. Bolhuis and co-workers on our article discussing the role of linezolid in treating multidrug-resistant (MDR) tuberculosis (TB) failures in India [1]. First, we would like to underline that our study was carried out in field conditions in a country with a high burden of MDR-TB cases and limited resources. We thank M.S. Bolhuis and co-workers for the opportunity to discuss the different perspectives of the Indian setting and those of a high-level tertiary hospital in a high-income country (India has one of the best existing TB control programmes). M.S. Bolhuis and co-workers correctly conclude that only a randomised trial comparing linezolid versus a placebo, in addition to an adequate background regimen using drug susceptibility testing (DST) and therapeutic drug monitoring (TDM), would provide comprehensive results on …