Scaling up interventions to achieve global tuberculosis control: progress and new developments

Decline in overall, smear-negative and HIV-positive TB incidence while smear-positive incidence stays stable in Guinea-Bissau 2004-2011

OBJECTIVE

To calculate Tuberculosis (TB) incidence rates in Guinea-Bissau over an 8-year period.

METHODS

Since 2003, a surveillance system has registered all TB cases in six suburban districts of Bissau. In this population-based prospective follow-up study, 1205 cases of pulmonary TB were identified between January 2004 and December 2011. Incidence rates were calculated using census data from the Bandim Health and Demographic Surveillance System (HDSS).

RESULTS

The overall incidence of pulmonary TB was 279 per 100,000 person-years of observation; the male incidence being 385, and the female 191. TB incidence rates increased significantly with age in both sexes, regardless of smear or HIV status. Despite a peak with unknown cause of 352 per 100,000 in 2007, the overall incidence of pulmonary TB declined over the period. The incidence of HIV infected TB cases declined significantly from 108 to 39 per 100,000, while the incidence of smear-positive TB cases remained stable; the overall figure was 188 per 100,000.

CONCLUSIONS

Overall incidence of pulmonary TB in Guinea-Bissau has declined from 2004 to 2011. The decline was also seen in the subgroups of smear-negative and HIV-positive TB cases, probably due to antiretroviral treatment. Smear-positive TB incidence remains stable over the period.

Development of cyclobutene- and cyclobutane-functionalized fatty acids with inhibitory activity against Mycobacterium tuberculosis

Eleven fatty acid analogues incorporating four-membered carbocycles (cyclobutenes, cyclobutanes, cyclobutanones, and cyclobutanols) were investigated for the ability to inhibit the growth of Mycobacterium smegmatis (Msm) and Mycobacterium tuberculosis (Mtb). A number of the analogues displayed inhibitory activity against both mycobacterial species in minimal media. Several of the molecules displayed potent levels of inhibition against Mtb, with MIC values equal to or below those observed with the anti-tuberculosis drugs D-cycloserine and isoniazid. In contrast, two of the analogues that display the greatest activity against Mtb failed to inhibit E. coli growth under either set of conditions. Thus, the active molecules identified herein may provide the basis for the development of anti-mycobacterial agents against Mtb.

Determinants of PCR performance (Xpert MTB/RIF), including bacterial load and inhibition, for TB diagnosis using specimens from different body compartments

The determinants of Xpert MTB/RIF sensitivity, a widely used PCR test for the diagnosis of tuberculosis (TB) are poorly understood. We compared culture time-to-positivity (TTP; a surrogate of bacterial load), MTB/RIF TB-specific and internal positive control (IPC)-specific C(T) values, and clinical characteristics in patients with suspected TB who provided expectorated (n = 438) or induced sputum (n = 128), tracheal aspirates (n = 71), bronchoalveolar lavage fluid (n = 152), pleural fluid (n = 76), cerebral spinal fluid (CSF; n = 152), pericardial fluid (n = 131), or urine (n = 173) specimens. Median bacterial load (TTP in days) was the strongest associate of MTB/RIF positivity in each fluid. TTP correlated with C(T) values in pulmonary specimens but not extrapulmonary specimens (Spearman's coefficient 0.5043 versus 0.1437; p = 0.030). Inhibition affected a greater proportion of pulmonary specimens than extrapulmonary specimens (IPC C(T) > 34: 6% (47/731) versus 1% (4/381; p < 0.0001). Pulmonary specimens had greater load than extrapulmonary specimens [TTPs (interquartile range) of 11 (7-16) versus 22 (18-33.5) days; p < 0.0001]. HIV-infection was associated with a decreased likelihood of MTB/RIF-positivity in pulmonary specimens but an increased likelihood in extrapulmonary specimens. Mycobacterial load, which displays significant variation across different body compartments, is the main determinant of MTB/RIF-positivity rather than PCR inhibition. MTB/RIF C(T) is a poor surrogate of load in extrapulmonary specimens.

Treatment outcomes in tuberculosis patients with diabetes: a polytomous analysis using Brazilian surveillance system

BACKGROUND

The impact of non-communicable diseases on tuberculosis incidence has received significant attention. It has been suggested that the risk of tuberculosis is higher among subjects with diabetes and these subjects also has poor TB treatment outcomes.This study was aimed at assessing the socio-demographic and clinical factors that may influence different outcome of TB in patients with DM (TB-DM) identified in the Brazilian national database from 2001 to 2011.

METHODS

TB-DM cases reported in the Brazilian information system were identified and compared.Covariates associated with the outcomes of interest (cure, default, deaths, and development of TB MDR) were included in a hierarchical regression model.

RESULTS

TB-DM cases increased from 380/100,000/year in 2001 to 6,150/100,000/year in 2011. Some of the main associations found are pointed. The odds of default was higher among those in the age group 20-39 years (OR = 2.07, 95%CI 1.32-3.24); alcoholics (OR = 2.17, 95%CI 1.86-2.54), and HIV/AIDS (OR = 2.16, 95%CI 1.70-2.74);positive monitoring smear (OR = 1.94, 95%CI 1.55-2.43); prior default (OR = 5.41, 95%CI 4.47-6.54), and unknown type of treatment (OR = 3.33, 95%CI 1.54-7.22). The odds of death was greater for subjects ≥60 years old (OR = 2.74, 95%CI 1.74-4.29); institutionalized in shelter (OR = 2.69, 95%CI 1.07-6.77); alcoholics (OR = 2.70, 95%CI 2.27-3.22); HIV/AIDS (OR = 2.87, 95%CI 2.13-3.86); pulmonary+extrapulmonary TB (OR = 2.49, 95%CI 1.79-3.46); with unknown type of treatment (OR = 14.12, 95%CI 7.04-28.32).Development of MDR TB was more related to relapse (OR = 9.60, 95%CI 6.07-15.14);previous default (OR = 17.13, 95%CI 9.58-30.63); and transfer of treatment center (OR = 7.87, 95%CI 4.74-13.07).

CONCLUSIONS

Older subjects and those with comorbidities and with a previous treatment of TB had poorest outcomes. TB control program in Brazil will need to expand efforts to focus on treatment of TB-DM patients to improve their cure rates in order to achieve the goals of tuberculosis elimination.

Worldwide increase in diabetes: implications for tuberculosis control

Diabetes presents a greater threat to global tuberculosis (TB) control than previously appreciated, with risk of reversing the achievements of several decades. An estimated 382 million people worldwide currently have diabetes, half of whom are undiagnosed. Most live in low- and middle-income countries alongside many of the two billion individuals infected with TB. Though the frequency of TB in type 1 diabetes was known for centuries, only recently have we observed the tripling of TB in type 2 diabetes, most significantly in high-burden TB populations such as in Peru, Russia, and the People's Republic of China. In India diabetes is estimated to have increased TB cases by 46% between 1998 and 2008. Diabetes is a greater long-term threat to TB control than human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) since ten-fold more people are affected by diabetes than HIV/AIDS in larger geographic areas. Diabetes in TB increases drug resistance, treatment failure, and mortality, and may increase the spread of drug-resistant strains. Delayed or missed diagnosis fuels transmission of TB and hinders control of diabetes. Tailored treatment for diabetes patients requires well-designed clinical trials. The World Health Organization (WHO) framework for care and control of diabetes and TB needs improved screening strategies. Determination of how best to establish bi-directional screening is hampered by lack of affordable and reliable methods. Recommendations include education of health care providers, patients, and communities. Structured diabetes programs with registries and effective follow-up could be modeled on and communicate with existing TB programs. Vital research should address new diagnostic tools, lowering cost and evaluation of intervention strategies, as well as better understanding of the impaired immune responses that make diabetes patients more susceptible to TB leading to targeted therapies. Solutions will require the combination of good science, good decision-making, adequate funding, and political will.

Isocitrate lyase mediates broad antibiotic tolerance in Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is a persistent intracellular pathogen intrinsically tolerant to most antibiotics. However, the specific factors that mediate this tolerance remain incompletely defined. Here we apply metabolomic profiling to discover a common set of metabolic changes associated with the activities of three clinically used tuberculosis drugs, isoniazid, rifampicin and streptomycin. Despite targeting diverse cellular processes, all three drugs trigger activation of Mtb's isocitrate lyases (ICLs), metabolic enzymes commonly assumed to be involved in replenishing of tricarboxylic acid (TCA) cycle intermediates. We further show that ICL-deficient Mtb strains are significantly more susceptible than wild-type Mtb to all three antibiotics, and that this susceptibility can be chemically rescued when Mtb is co-incubated with an antioxidant. These results identify a previously undescribed role for Mtb's ICLs in antioxidant defense as a mechanism of antibiotic tolerance.

1,4-azaindole, a potential drug candidate for treatment of tuberculosis

New therapeutic strategies against multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis are urgently required to combat the global tuberculosis (TB) threat. Toward this end, we previously reported the identification of 1,4-azaindoles, a promising class of compounds with potent antitubercular activity through noncovalent inhibition of decaprenylphosphoryl-β-D-ribose 2'-epimerase (DprE1). Further, this series was optimized to improve its physicochemical properties and pharmacokinetics in mice. Here, we describe the short-listing of a potential clinical candidate, compound 2, that has potent cellular activity, drug-like properties, efficacy in mouse and rat chronic TB infection models, and minimal in vitro safety risks. We also demonstrate that the compounds, including compound 2, have no antagonistic activity with other anti-TB drugs. Moreover, compound 2 shows synergy with PA824 and TMC207 in vitro, and the synergy effect is translated in vivo with TMC207. The series is predicted to have a low clearance in humans, and the predicted human dose for compound 2 is ≤1 g/day. Altogether, our data suggest that a 1,4-azaindole (compound 2) is a promising candidate for the development of a novel anti-TB drug.

Use of collateral sensitivity networks to design drug cycling protocols that avoid resistance development

New drug deployment strategies are imperative to address the problem of drug resistance, which is limiting the management of infectious diseases and cancers. We evolved resistance in Escherichia coli toward 23 drugs used clinically for treating bacterial infections and mapped the resulting collateral sensitivity and resistance profiles, revealing a complex collateral sensitivity network. On the basis of these data, we propose a new treatment framework--collateral sensitivity cycling--in which drugs with compatible collateral sensitivity profiles are used sequentially to treat infection and select against drug resistance development. We identified hundreds of such drug sets and demonstrated that the antibiotics gentamicin and cefuroxime can be deployed cyclically such that the treatment regimen selected against resistance to either drug. We then validated our findings with related bacterial pathogens. These results provide proof of principle for collateral sensitivity cycling as a sustainable treatment paradigm that may be generally applicable to infectious diseases and cancer.

Lead optimization of 1,4-azaindoles as antimycobacterial agents

In a previous report, we described the discovery of 1,4-azaindoles, a chemical series with excellent in vitro and in vivo antimycobacterial potency through noncovalent inhibition of decaprenylphosphoryl-β-d-ribose-2'-epimerase (DprE1). Nevertheless, high mouse metabolic turnover and phosphodiesterase 6 (PDE6) off-target activity limited its advancement. Herein, we report lead optimization of this series, culminating in potent, metabolically stable compounds that have a robust pharmacokinetic profile without any PDE6 liability. Furthermore, we demonstrate efficacy for 1,4-azaindoles in a rat chronic TB infection model. We believe that compounds from the 1,4-azaindole series are suitable for in vivo combination and safety studies.

Tuberculosis prevalence in China, 1990-2010; a longitudinal analysis of national survey data

BACKGROUND

China scaled up a tuberculosis control programme (based on the directly observed treatment, short-course [DOTS] strategy) to cover half the population during the 1990s, and to the entire population after 2000. We assessed the effect of the programme.

METHODS

In this longitudinal analysis, we compared data from three national tuberculosis prevalence surveys done in 1990, 2000, and 2010. The 2010 survey screened 252,940 eligible individuals aged 15 years and older at 176 investigation points, chosen by stratified random sampling from all 31 mainland provinces. All individuals had chest radiographs taken. Those with abnormal radiographs, persistent cough, or both, were classified as having suspected tuberculosis. Tuberculosis was diagnosed by chest radiograph, sputum-smear microscopy, and culture. Trained staff interviewed each patient with tuberculosis. The 1990 and 2000 surveys were reanalysed and compared with the 2010 survey.

FINDINGS

From 1990 to 2010, the prevalence of smear-positive tuberculosis decreased from 170 cases (95% CI 166-174) to 59 cases (49-72) per 100,000 population. During the 1990s, smear-positive prevalence fell only in the provinces with the DOTS programme; after 2000, prevalence decreased in all provinces. The percentage reduction in smear-positive prevalence was greater for the decade after 2000 than the decade before (57% vs 19%; p<0.0001). 70% of the total reduction in smear-positive prevalence (78 of 111 cases per 100,000 population) occurred after 2000. Of these cases, 68 (87%) were in known cases-ie, cases diagnosed with tuberculosis before the survey. Of the known cases, the proportion treated by the public health system (using the DOTS strategy) increased from 59 (15%) of 370 cases in 2000 to 79 (66%) of 123 cases in 2010, contributing to reduced proportions of treatment default (from 163 [43%] of 370 cases to 35 [22%] of 123 cases) and retreatment cases (from 312 [84%] of 374 cases to 48 [31%] of 137 cases; both p<0.0001).

INTERPRETATION

In 20 years, China more than halved its tuberculosis prevalence. Marked improvement in tuberculosis treatment, driven by a major shift in treatment from hospitals to the public health centres (that implemented the DOTS strategy) was largely responsible for this epidemiological effect.

FUNDING

Chinese Ministry of Health.

Recent developments in tuberculosis vaccines

Substantial efforts have been made over the past decade to develop vaccines against tuberculosis. We review recent developments in tuberculosis vaccines in the global portfolio, including those designed for use in a prophylactic setting, either alone or as boosts to Bacille Calmette-Guérin, and therapeutic vaccines designed to improve chemotherapy. While there is no doubt that progress is still being made, there are limitations to our animal model screening processes, which are further amplified by the lack of understanding of the immunological responses involved and the precise type of long-lived immunity that new vaccines need to induce. The challenge ahead is to optimize the planning for advanced clinical trials in poor endemic settings, which could be greatly facilitated by identifying correlates of protection.

The Bandim TBscore--reliability, further development, and evaluation of potential uses

Background

The tuberculosis (TB) case detection rate has stagnated at 60% due to disorganized case finding and insensitivity of sputum smear microscopy. Of the identified TB cases, 4% die while being treated, monitored with tools that insufficiently predict failure/mortality.

Objective

To explore the TBscore, a recently proposed clinical severity measure for pulmonary TB (PTB) patients, and to refine, validate, and investigate its place in case finding.

Design

The TBscore’s inter-observer agreement was assessed and compared to the Karnofsky Performance Score (KPS) (paper I). The TBscore’s variables underlying constructs were assessed, sorting out unrelated items, proposing a more easily assessable TBscoreII, which was validated internally and externally (paper II). Finally, TBscore and TBscoreII’s place in PTB-screening was examined in paper III.

Results

The inter-observer variability when grading PTB patients into severity classes was moderate for both TBscore (κ_W=0.52, 95% CI 0.46–0.56) and KPS (κ_W=0.49, 95% CI 0.33–0.65). KPS was influenced by HIV status, whereas TBscore was unaffected by it. In paper II, proposed TBscoreII was validated internally, in Guinea-Bissau, and externally, in Ethiopia. In both settings, a failure to bring down the score by ≥25% from baseline to 2 months of treatment predicted subsequent failure (p=0.007). Finally, in paper III, TBscore and TBscoreII were assessed in health-care-seeking adults and found to be higher in PTB-diagnosed patients, 4.9 (95% CI 4.6–5.2) and 3.9 (95% CI 3.8–4.0), respectively, versus patients not diagnosed with PTB, 3.0 (95% CI 2.7–3.2) and 2.4 (95% CI 2.3–2.5), respectively. Had we referred only patients with cough >2 weeks to sputum smear, we would have missed 32.1% of the smear confirmed cases in our cohort. A TBscoreII>=2 missed 8.6%.

Conclusions

TBscore and TBscoreII are useful monitoring tools for PTB patients on treatment, as they could fill the void which currently exists in risk grading of patients. They may also have a role in PTB screening; however, this requires our findings to be repeated elsewhere.

Facing multi-drug resistant tuberculosis

Multi-drug resistant tuberculosis (MDR-TB) is caused by Mycobacterium tuberculosis strains resistant to at least two of the most effective anti-tuberculosis drugs (i.e., isoniazid and rifampicin). Therapeutic regimens based on second- and third-line anti-tuberculosis medicines showed poor efficacy, safety, and tolerability profiles. It was estimated that in 2012 the multi-drug resistant tuberculosis incidence ranged from 300,000 to 600,000 cases, mainly diagnosed in the Eastern European and Central Asian countries. The highest proportion of cases is among individuals previously exposed to anti-tuberculosis drugs. Three main conditions can favour the emergence and spread of multi-drug resistant tuberculosis: the poor implementation of the DOTS strategy, the shortage or the poor quality of the anti-tuberculosis drugs, and the poor therapeutic adherence of the patients to the prescribed regimens. Consultation with tuberculosis experts (e.g., consilium) is crucial to tailor the best anti-tuberculosis therapy. New therapeutic options are necessary: bedaquiline and delamanid seem promising drugs; in particular, during the development phase they demonstrated a protective effect against the emergence of further resistances towards the backbone drugs. In the recent past, other antibiotics have been administered off-label: the most relevant efficacy, safety, and tolerability profile was proved in linezolid-, meropenem/clavulanate-, cotrimoxazole-containing regimens. New research and development activities are needed in the diagnostic, therapeutic, preventive fields.

Joint failure after steroid therapy in tuberculous encephalitis

We report a case of multifocal avascular osteonecrosis (AVN) following steroid administration in a case of tuberculous encephalitis in a young patient. The risk of joint-related AVN as a side effect of adjunctive steroid therapy should be taken into consideration when evaluating the dosage and treatment duration in tuberculous encephalitis.

Functional Signatures of Human CD4 and CD8 T Cell Responses to Mycobacterium tuberculosis

With 1.4 million deaths and 8.7 million new cases in 2011, tuberculosis (TB) remains a global health care problem and together with HIV and Malaria represents one of the three infectious diseases world-wide. Control of the global TB epidemic has been impaired by the lack of an effective vaccine, by the emergence of drug-resistant forms of Mycobacterium tuberculosis (Mtb) and by the lack of sensitive and rapid diagnostics. It is estimated, by epidemiological reports, that one third of the world’s population is latently infected with Mtb, but the majority of infected individuals develop long-lived protective immunity, which controls and contains Mtb in a T cell-dependent manner. Development of TB disease results from interactions among the environment, the host, and the pathogen, and known risk factors include HIV co-infection, immunodeficiency, diabetes mellitus, overcrowding, malnutrition, and general poverty; therefore, an effective T cell response determines whether the infection resolves or develops into clinically evident disease. Consequently, there is great interest in determining which T cells subsets mediate anti-mycobacterial immunity, delineating their effector functions. On the other hand, many aspects remain unsolved in understanding why some individuals are protected from Mtb infection while others go on to develop disease. Several studies have demonstrated that CD4⁺ T cells are involved in protection against Mtb, as supported by the evidence that CD4⁺ T cell depletion is responsible for Mtb reactivation in HIV-infected individuals. There are many subsets of CD4⁺ T cells, such as T-helper 1 (Th1), Th2, Th17, and regulatory T cells (Tregs), and all these subsets co-operate or interfere with each other to control infection; the dominant subset may differ between active and latent Mtb infection cases. Mtb-specific-CD4⁺ Th1 cell response is considered to have a protective role for the ability to produce cytokines such as IFN-γ or TNF-α that contribute to the recruitment and activation of innate immune cells, like monocytes and granulocytes. Thus, while other antigen (Ag)-specific T cells such as CD8⁺ T cells, natural killer (NK) cells, γδ T cells, and CD1-restricted T cells can also produce IFN-γ during Mtb infection, they cannot compensate for the lack of CD4⁺ T cells. The detection of Ag-specific cytokine production by intracellular cytokine staining (ICS) and the use of flow cytometry techniques are a common routine that supports the studies aimed at focusing the role of the immune system in infectious diseases. Flow cytometry permits to evaluate simultaneously the presence of different cytokines that can delineate different subsets of cells as having “multifunctional/polyfunctional” profile. It has been proposed that polyfunctional T cells, are associated with protective immunity toward Mtb, in particular it has been highlighted that the number of Mtb-specific T cells producing a combination of IFN-γ, IL-2, and/or TNF-α may be correlated with the mycobacterial load, while other studies have associated the presence of this particular functional profile as marker of TB disease activity. Although the role of CD8 T cells in TB is less clear than CD4 T cells, they are generally considered to contribute to optimal immunity and protection. CD8 T cells possess a number of anti-microbial effector mechanisms that are less prominent or absent in CD4 Th1 and Th17 T cells. The interest in studying CD8 T cells that are either MHC-class Ia or MHC-class Ib-restricted, has gained more attention. These studies include the role of HLA-E-restricted cells, lung mucosal-associated invariant T-cells (MAIT), and CD1-restricted cells. Nevertheless, the knowledge about the role of CD8⁺ T cells in Mtb infection is relatively new and recent studies have delineated that CD8 T cells, which display a functional profile termed “multifunctional,” can be a better marker of protection in TB than CD4⁺ T cells. Their effector mechanisms could contribute to control Mtb infection, as upon activation, CD8 T cells release cytokines or cytotoxic molecules, which cause apoptosis of target cells. Taken together, the balance of the immune response in the control of infection and possibly bacterial eradication is important in understanding whether the host immune response will be appropriate in contrasting the infection or not, and, consequently, the inability of the immune response, will determine the dissemination and the transmission of bacilli to new subjects. In conclusion, the recent highlights on the role of different functional signatures of T cell subsets in the immune response toward Mtb infection will be discerned in this review, in order to summarize what is known about the immune response in human TB. In particular, we will discuss the role of CD4 and CD8 T cells in contrasting the advance of the intracellular pathogen in already infected people or the progression to active disease in subjects with latent infection. All the information will be aimed at increasing the knowledge of this complex disease in order to improve diagnosis, prognosis, drug treatment, and vaccination.

Nutritional supplementation increases rifampin exposure among tuberculosis patients coinfected with HIV

Nutritional supplementation to tuberculosis (TB) patients has been associated with increased weight and reduced mortality, but its effect on the pharmacokinetics of first-line anti-TB drugs is unknown. A cohort of 100 TB patients (58 men; median age, 35 [interquartile range {IQR}, 29 to 40] years, and median body mass index [BMI], 18.8 [17.3 to 19.9] kg/m(2)) were randomized to receive nutritional supplementation during the intensive phase of TB treatment. Rifampin plasma concentrations were determined after 1 week and 2 months of treatment. The effects of nutritional supplementation, HIV, time on treatment, body weight, and SLCO1B1 rs4149032 genotype were examined using a population pharmacokinetic model. The model adjusted for body size via allometric scaling, accounted for clearance autoinduction, and detected an increase in bioavailability (+14%) for the patients in the continuation phase. HIV coinfection in patients not receiving the supplementation was found to decrease bioavailability by 21.8%, with a median maximum concentration of drug in serum (Cmax) and area under the concentration-time curve from 0 to 24 h (AUC0-24) of 5.6 μg/ml and 28.6 μg · h/ml, respectively. HIV-coinfected patients on nutritional supplementation achieved higher Cmax and AUC0-24 values of 6.4 μg/ml and 31.6 μg · h/ml, respectively, and only 13.3% bioavailability reduction. No effect of the SLCO1B1 rs4149032 genotype was observed. In conclusion, nutritional supplementation during the first 2 months of TB treatment reduces the decrease in rifampin exposure observed in HIV-coinfected patients but does not affect exposure in HIV-uninfected patients. If confirmed in other studies, the use of defined nutritional supplementation in HIV-coinfected TB patients should be considered in TB control programs. (This study has the controlled trial registration number ISRCTN 16552219.).

Extensively drug-resistant tuberculosis: epidemiology and management

The advent of antibiotics for the treatment of tuberculosis (TB) represented a major breakthrough in the fight against the disease. However, since its first use, antibiotic therapy has been associated with the emergence of resistance to drugs. The incorrect use of anti-TB drugs, either due to prescription errors, low patient compliance, or poor quality of drugs, led to the widespread emergence of Mycobacterium tuberculosis strains with an expanding spectrum of resistance. The spread of multidrug-resistant (MDR) strains (ie, strains resistant to both isoniazid and rifampicin) has represented a major threat to TB control since the 1990s. In 2006, the first cases of MDR strains with further resistance to fluoroquinolone and injectable drugs were described and named extensively drug-resistant TB (XDR-TB). The emergence of XDR-TB strains is a result of mismanagement of MDR cases, and treatment relies on drugs that are less potent and more toxic than those used to treat drug-susceptible or MDR strains. Furthermore, treatment success is lower and mortality higher than achieved in MDR-TB cases, and the number of drugs necessary in the intensive phase of treatment may be higher than the four drugs recommended for MDR-TB. Linezolid may represent a valuable drug to treat cases of XDR-TB. Delamanid, bedaquiline, and PA-824 are new anti-TB agents in the development pipeline that have the potential to enhance the cure rate of XDR-TB. The best measures to prevent new cases of XDR-TB are the correct management of MDR-TB patients, early detection, and proper treatment of existing patients with XDR-TB.

Allostery and compartmentalization: old but not forgotten

Homeostasis is an essential capability of all cells mediated by complex and diverse regulatory networks. Despite this complexity, many of the fundamental regulatory mechanisms used by cells have been evolutionarily conserved. It is thus somewhat surprising that the apparent physiologic significance of these mechanisms has been experimentally neglected. Here, we review 2 widely recognized regulatory mechanisms, allostery and compartmentalization, which exemplify this dissociation in our current understanding of the microbial pathogen, Mycobacterium tuberculosis.

Assessment of Mycobacterium tuberculosis pantothenate kinase vulnerability through target knockdown and mechanistically diverse inhibitors

Pantothenate kinase (PanK) catalyzes the phosphorylation of pantothenate, the first committed and rate-limiting step toward coenzyme A (CoA) biosynthesis. In our earlier reports, we had established that the type I isoform encoded by the coaA gene is an essential pantothenate kinase in Mycobacterium tuberculosis, and this vital information was then exploited to screen large libraries for identification of mechanistically different classes of PanK inhibitors. The present report summarizes the synthesis and expansion efforts to understand the structure-activity relationships leading to the optimization of enzyme inhibition along with antimycobacterial activity. Additionally, we report the progression of two distinct classes of inhibitors, the triazoles, which are ATP competitors, and the biaryl acetic acids, with a mixed mode of inhibition. Cocrystallization studies provided evidence of these inhibitors binding to the enzyme. This was further substantiated with the biaryl acids having MIC against the wild-type M. tuberculosis strain and the subsequent establishment of a target link with an upshift in MIC in a strain overexpressing PanK. On the other hand, the ATP competitors had cellular activity only in a M. tuberculosis knockdown strain with reduced PanK expression levels. Additionally, in vitro and in vivo survival kinetic studies performed with a M. tuberculosis PanK (MtPanK) knockdown strain indicated that the target levels have to be significantly reduced to bring in growth inhibition. The dual approaches employed here thus established the poor vulnerability of PanK in M. tuberculosis.

Empirical treatment for TB in HIV: lessons from a cohort study of people living with HIV treated in Recife, Brazil

Background

Tuberculosis (TB) is the leading cause of death related to HIV worldwide. This study analyzes the survival of People Living with HIV (PLHIV) reporting cough without bacteriological confirmation of TB and identify factors associated with death.

Methods

Prospective cohort with a consecutive sample of PLHIV, aged ≥ 18 years. Patient inclusion criteria were complaint of current cough of any duration at the time of the first study interview or during their subsequent routine visits to health services and for whom AFB sputum smear was either negative or not performed during the whole follow-up period. Kaplan-Meier method was used to calculate the probability of survival. We estimated the Hazard Ratio (HR) in bivariate and multivariate Cox regression analyses.

Results

Mortality was 4.6 per 100 py; 73% were receiving HAART at recruitment. Average time from the first recorded date of cough until empirical treatment for tuberculosis was six months. Mortality was higher when the CD4 count was low (HR = 5.3; CI 95%: 3.2-9.0; p = 0.000), in those with anemia (HR = 3.0; CI 95%: 1.6-5.6; p = 0.001) and with abnormal chest X-rays (HR = 2.4; CI 95%: 1.4-4.0; p = 0.001). Mortality was higher in those receiving empirical TB treatment (HR = 2.4; CI 95%: 1.4-4.0; p = 0.002), but only in those with normal X-rays, no history of tuberculosis and no bacteriology requests. Empirical treatment for TB was more frequent in PLHIV with low CD4 counts, anemia, history of opportunistic infections, weight loss, previous tuberculosis, negative bacteriology test (as opposed to not having a test) and abnormal chest X-ray.

Conclusions

Higher mortality in PLHIV reporting a current cough without bacteriological confirmation of tuberculosis was identified for those with a CD4 cell count <200, abnormal chest X-ray, anemia and empirical treatment for tuberculosis. Mortality was not significantly higher in those empirically treated for TB, who had three characteristics suggestive of the disease (abnormal chest X-ray, history of TB treatment, AFB sputum smear or M.tb culture testing). Routine cohorts are not an adequate setting to evaluate the impact of empirical treatment for TB on the mortality of PLHIV.

Diabetes mellitus and risk of all-cause mortality among patients with tuberculosis in the state of Georgia, 2009-2012

PURPOSE

To estimate the association between diabetes mellitus (DM) and all-cause mortality during tuberculosis (TB) treatment.

METHODS

From 2009 to 2012, a retrospective cohort study among reported TB cases in Georgia was conducted. Patients aged 16 years or older were classified by DM and human immunodeficiency virus (HIV) status at the time of TB diagnosis and followed during TB treatment to assess mortality. Hazard ratios were used to estimate the association between DM and death.

RESULTS

Among 1325 patients with TB disease, 151 (11.4%) had DM, 147 (11.1%) were HIV-infected, and seven (0.5%) had both DM and HIV. Patients with TB-DM were more likely to have cavitary lung disease compared with those with TB alone (51.0% vs. 34.7%) and those with TB-HIV were more likely to have military/disseminated disease (12.9% vs. 3.4%) and resistance to rifampin or isoniazid (21.8% vs. 9.0%) compared with those without HIV infection (P < .05). In multivariable analysis, DM was not associated with death during TB treatment (hazard ratio, 1.22; 95% confidence interval, 0.70-2.12) or any death (adjusted odds ratio, 1.05; 95% confidence interval, 0.60-1.84).

CONCLUSIONS

Among TB patients in Georgia, the prevalence of comorbid DM and coinfection with HIV was nearly identical. In adjusted models, TB patients with DM did not have increased risk of all-cause mortality.

Feasibility, accuracy, and clinical effect of point-of-care Xpert MTB/RIF testing for tuberculosis in primary-care settings in Africa: a multicentre, randomised, controlled trial

BACKGROUND

The Xpert MTB/RIF test for tuberculosis is being rolled out in many countries, but evidence is lacking regarding its implementation outside laboratories, ability to inform same-day treatment decisions at the point of care, and clinical effect on tuberculosis-related morbidity. We aimed to assess the feasibility, accuracy, and clinical effect of point-of-care Xpert MTB/RIF testing at primary-care health-care facilities in southern Africa.

METHODS

In this pragmatic, randomised, parallel-group, multicentre trial, we recruited adults with symptoms suggestive of active tuberculosis from five primary-care health-care facilities in South Africa, Zimbabwe, Zambia, and Tanzania. Eligible patients were randomly assigned using pregenerated tables to nurse-performed Xpert MTB/RIF at the clinic or sputum smear microscopy. Participants with a negative test result were empirically managed according to local WHO-compliant guidelines. Our primary outcome was tuberculosis-related morbidity (measured with the TBscore and Karnofsky performance score [KPS]) in culture-positive patients who had begun anti-tuberculosis treatment, measured at 2 months and 6 months after randomisation, analysed by intention to treat. This trial is registered with Clinicaltrials.gov, number NCT01554384.

FINDINGS

Between April 12, 2011, and March 30, 2012, we randomly assigned 758 patients to smear microscopy (182 culture positive) and 744 to Xpert MTB/RIF (185 culture positive). Median TBscore in culture-positive patients did not differ between groups at 2 months (2 [IQR 0-3] in the smear microscopy group vs 2 [0·25-3] in the MTB/RIF group; p=0·85) or 6 months (1 [0-3] vs 1 [0-3]; p=0·35), nor did median KPS at 2 months (80 [70-90] vs 90 [80-90]; p=0·23) or 6 months (100 [90-100] vs 100 [90-100]; p=0·85). Point-of-care MTB/RIF had higher sensitivity than microscopy (154 [83%] of 185 vs 91 [50%] of 182; p=0·0001) but similar specificity (517 [95%] 544 vs 540 [96%] of 560; p=0·25), and had similar sensitivity to laboratory-based MTB/RIF (292 [83%] of 351; p=0·99) but higher specificity (952 [92%] of 1037; p=0·0173). 34 (5%) of 744 tests with point-of-care MTB/RIF and 82 (6%) of 1411 with laboratory-based MTB/RIF failed (p=0·22). Compared with the microscopy group, more patients in the MTB/RIF group had a same-day diagnosis (178 [24%] of 744 vs 99 [13%] of 758; p<0·0001) and same-day treatment initiation (168 [23%] of 744 vs 115 [15%] of 758; p=0·0002). Although, by end of the study, more culture-positive patients in the MTB/RIF group were on treatment due to reduced dropout (15 [8%] of 185 in the MTB/RIF group did not receive treatment vs 28 [15%] of 182 in the microscopy group; p=0·0302), the proportions of all patients on treatment in each group by day 56 were similar (320 [43%] of 744 in the MTB/RIF group vs 317 [42%] of 758 in the microscopy group; p=0·6408).

INTERPRETATION

Xpert MTB/RIF can be accurately administered by a nurse in primary-care clinics, resulting in more patients starting same-day treatment, more culture-positive patients starting therapy, and a shorter time to treatment. However, the benefits did not translate into lower tuberculosis-related morbidity, partly because of high levels of empirical-evidence-based treatment in smear-negative patients.

FUNDING

European and Developing Countries Clinical Trials Partnership, National Research Foundation, and Claude Leon Foundation.

Tuberculosis vaccine with high predicted population coverage and compatibility with modern diagnostics

A central goal in vaccine research is the identification of relevant antigens. The Mycobacterium tuberculosis chromosome encodes 23 early secretory antigenic target (ESAT-6) family members that mostly are localized as gene pairs. In proximity to five of the gene pairs are ESX secretion systems involved in the secretion of the ESAT-6 family proteins. Here, we performed a detailed and systematic investigation of the vaccine potential of five possible Esx dimer substrates, one for each of the five ESX systems. On the basis of gene transcription during infection, immunogenicity, and protective capacity in a mouse aerosol challenge model, we identified the ESX dimer substrates EsxD-EsxC, ExsG-EsxH, and ExsW-EsxV as the most promising vaccine candidates and combined them in a fusion protein, H65. Vaccination with H65 gave protection at the level of bacillus Calmette-Guérin, and the fusion protein exhibited high predicted population coverage in high endemic regions. H65 thus constitutes a promising vaccine candidate devoid of antigen 85 and fully compatible with current ESAT-6 and culture filtrate protein 10-based diagnostics.

Modifiable factors associated with tuberculosis disease in children: a case-control study

We conducted a case-control study among children in Lima, Peru to identify factors associated with tuberculosis disease. Known close contact with someone with tuberculosis disease, prior hospitalization, and history of anemia were associated with a higher tuberculosis disease rate. Consumption of fruits/vegetables ≥5 days/week was associated with a lower rate. Isoniazid uptake was low among children with a known contact.

N-Arylalkylbenzo[d]thiazole-2-carboxamides as anti-mycobacterial agents: design, new methods of synthesis and biological evaluation

Benzothiazole-2-carboxyarylalkylamides are reported as a new class of potent anti-mycobacterial agents.

Incidence and mortality of tuberculosis disease in Spain between 1997 and 2010: impact of human immunodeficiency virus (HIV) status

OBJECTIVE

To estimate incidence and mortality of TB disease in Spain, as well as TB recurrence and its mortality, and to analyse its trend from 1997 to 2010 in human immunodeficiency virus (HIV)-infected patients (HIV(+) group), compared to HIV-uninfected subjects (HIV(-) group).

METHODS

We performed a retrospective study using data from Minimum Basic Data Set. The outcome variables were new TB diagnosis, TB recurrences, and mortality; which were analysed through three calendar periods related to widespread use of combination antiretroviral therapy (cART): a) From 1997 to 1999 for early-period cART; b) from 2000 to 2003 for mid-period cART; and c) from 2004 to 2008 for late-period cART.

RESULTS

We studied 86,093 HIV-uninfected patients and 17,031 HIV infected patients. TB diagnosis in HIV(-) group (events per 100,000 patients-yr) decreased from 20.16 (1997-1999) to 16.31 (2000-2003; p < 0.001), and later to 13.48 (2004-2010; p < 0.001); and among HIV(+) group (events per 1000 patients-yr) it decreased from 19.23 (1997-1999) to 10.93 (2000-2003; p < 0.001), and later to 6.35 (2004-2010; p < 0.001). For the mortality, HIV(-) group (events per 1,000,000 patients-yr) decreased from 11.5 (1997-1999) to 9.8 (2000-2003; p < 0.001), and later to 7.2 (2004-2010; p < 0.001); and HIV(+) group (events per 10,000 patients-yr) decreased from 20.69 (1997-1999) to 13.20 (2000-2003; p < 0.001), and later to 6.83 (2004-2010; p < 0.001). During the whole period, the diagnostic rate and mortality of TB remained 100-fold higher in HIV(+) group than HIV(-) group (p < 0.001). Moreover, HIV (+) group had higher percentage of patients with TB recurrence than HIV(-) group (p < 0.001).

CONCLUSION

TB diagnosis and mortality decreased in Spain between 1997 and 2010, in both HIV infected patients and people without HIV infection; but these rates remained higher in HIV infected patients.

Compliance with postexposure screening and treatment of latent tuberculosis infection among healthcare workers in a tertiary care hospital in Saudi Arabia

BACKGROUND

Controlling tuberculosis (TB) infection among occupationally exposed healthcare workers (HCWs) may be challenging.

METHODS

We retrospectively reviewed clinical records of HCWs who were exposed to patients diagnosed with infectious TB at King Abdulaziz Medical City, Riyadh, Saudi Arabia, between 2008 and 2010. The collected data included baseline tuberculin skin test (TST) status, potential predictors of TST positivity, postexposure diagnosis of latent TB infection (LTBI), and postexposure compliance with LTBI therapy.

RESULTS

Thirteen patients were diagnosed with infectious pulmonary TB during the study period. A total of 298 HCWs met our definition for exposure. Exposed HCWs tended to be female (62.9%), non-Saudi (83.9%), nurses (68.6%), or respiratory therapists (24.0%) working in critical care locations (72.8%). Baseline (preemployment) TST documentation existed for 41.3% (123/298). Among those with documented baseline TSTs, 51.2% (63/123) were positive, representing 21.1% (63/298) of all HCWs. Only 48.9% (115/235) of exposed HCWs who had negative or unknown preexposure TST status had their TST tested after exposure. Approximately 46.1% (53/115) of them were diagnosed with postexposure LTBI, and 92.5% (49/53) of them were prescribed LTBI therapy. Among those, 93.9% (46/49) started LTBI therapy; however, 82.6% (38/46) failed to complete the recommended course.

CONCLUSIONS

We found low rates of baseline TST documentation and postexposure screening among exposed HCWs. Compliance with initiating postexposure isoniazid prophylaxis among HCWs was fair, but only a small fraction of those who started prophylaxis completed the recommended course of therapy. These findings suggest substantial opportunities to implement administrative measures to enhance LTBI management among HCWs.

The structure of Rv3717 reveals a novel amidase from Mycobacterium tuberculosis

Bacterial N-acetylmuramoyl-L-alanine amidases are cell-wall hydrolases that hydrolyze the bond between N-acetylmuramic acid and L-alanine in cell-wall glycopeptides. Rv3717 of Mycobacterium tuberculosis has been identified as a unique autolysin that lacks a cell-wall-binding domain (CBD) and its structure has been determined to 1.7 Å resolution by the Pt-SAD phasing method. Rv3717 possesses an α/β-fold and is a zinc-dependent hydrolase. The structure reveals a short flexible hairpin turn that partially occludes the active site and may be involved in autoregulation. This type of autoregulation of activity of PG hydrolases has been observed in Bartonella henselae amidase (AmiB) and may be a general mechanism used by some of the redundant amidases to regulate cell-wall hydrolase activity in bacteria. Rv3717 utilizes its net positive charge for substrate binding and exhibits activity towards a broad spectrum of substrate cell walls. The enzymatic activity of Rv3717 was confirmed by isolation and identification of its enzymatic products by LC/MS. These studies indicate that Rv3717, an N-acetylmuramoyl-L-alanine amidase from M. tuberculosis, represents a new family of lytic amidases that do not have a separate CBD and are regulated conformationally.

Azaindoles: noncovalent DprE1 inhibitors from scaffold morphing efforts, kill Mycobacterium tuberculosis and are efficacious in vivo

We report 1,4-azaindoles as a new inhibitor class that kills Mycobacterium tuberculosis in vitro and demonstrates efficacy in mouse tuberculosis models. The series emerged from scaffold morphing efforts and was demonstrated to noncovalently inhibit decaprenylphosphoryl-β-D-ribose2'-epimerase (DprE1). With "drug-like" properties and no expectation of pre-existing resistance in the clinic, this chemical class has the potential to be developed as a therapy for drug-sensitive and drug-resistant tuberculosis.

Prime-boost with Mycobacterium smegmatis recombinant vaccine improves protection in mice infected with Mycobacterium tuberculosis

The development of a new vaccine as a substitute for Bacillus Calmette-Guerin or to improve its efficacy is one of the many World Health Organization goals to control tuberculosis. Mycobacterial vectors have been used successfully in the development of vaccines against tuberculosis. To enhance the potential utility of Mycobacterium smegmatis as a vaccine, it was transformed with a recombinant plasmid containing the partial sequences of the genes Ag85c, MPT51, and HspX (CMX) from M. tuberculosis. The newly generated recombinant strain mc(2)-CMX was tested in a murine model of infection. The recombinant vaccine induced specific IgG1 or IgG2a responses to CMX. CD4(+) and CD8(+) T cells from the lungs and spleen responded ex vivo to CMX, producing IFN-γ, IL17, TNF-α, and IL2. The vaccine thus induced a significant immune response in mice. Mice vaccinated with mc(2)-CMX and challenged with M. tuberculosis showed better protection than mice immunized with wild-type M. smegmatis or BCG. To increase the safety and immunogenicity of the CMX antigens, we used a recombinant strain of M. smegmatis, IKE (immune killing evasion), to express CMX. The recombinant vaccine IKE-CMX induced a better protective response than mc(2)-CMX. The data presented here suggest that the expression of CMX antigens improves the immune response and the protection induced in mice when M. smegmatis is used as vaccine against tuberculosis.

Gr1(int)CD11b+ myeloid-derived suppressor cells in Mycobacterium tuberculosis infection

BACKGROUND

Tuberculosis is one of the world's leading killers, stealing 1.4 million lives and causing 8.7 million new and relapsed infections in 2011. The only vaccine against tuberculosis is BCG which demonstrates variable efficacy in adults worldwide. Human infection with Mycobacterium tuberculosis results in the influx of inflammatory cells to the lung in an attempt to wall off bacilli by forming a granuloma. Gr1(int)CD11b(+) cells are called myeloid-derived suppressor cells (MDSC) and play a major role in regulation of inflammation in many pathological conditions. Although MDSC have been described primarily in cancer their function in tuberculosis remains unknown. During M. tuberculosis infection it is crucial to understand the function of cells involved in the regulation of inflammation during granuloma formation. Understanding their relative impact on the bacilli and other cellular phenotypes is necessary for future vaccine and drug design.

METHODOLOGY/PRINCIPAL FINDINGS

We compared the bacterial burden, lung pathology and Gr1(int)CD11b(+) myeloid-derived suppressor cell immune responses in M. tuberculosis infected NOS2-/-, RAG-/-, C3HeB/FeJ and C57/BL6 mice. Gr-1(+) cells could be found on the edges of necrotic lung lesions in NOS2-/-, RAG-/-, and C3HeB/FeJ, but were absent in wild-type mice. Both populations of Gr1(+)CD11b(+) cells expressed high levels of arginase-1, and IL-17, additional markers of myeloid derived suppressor cells. We then sorted the Gr1(hi) and Gr1(int) populations from M. tuberculosis infected NOS-/- mice and placed the sorted both Gr1(int) populations at different ratios with naïve or M. tuberculosis infected splenocytes and evaluated their ability to induce activation and proliferation of CD4+T cells. Our results showed that both Gr1(hi) and Gr1(int) cells were able to induce activation and proliferation of CD4+ T cells. However this response was reduced as the ratio of CD4(+) T to Gr1(+) cells increased. Our results illustrate a yet unrecognized interplay between Gr1(+) cells and CD4(+) T cells in tuberculosis.

Minding the gaps: metabolomics mends functional genomics

Two recent studies in PNAS and Nat Chem Biol highlight the power of modern mass‐spectrometry techniques for enzyme discovery applied to microbiology. In so doing, they have uncovered new potential targets for the treatment of tuberculosis.

Drug-resistant tuberculosis

PURPOSE OF REVIEW

This review discusses the recent evidence on epidemiology, diagnosis, and treatment of drug-resistant and multidrug-resistant (MDR) tuberculosis (TB), an area where solutions for better diagnosis and treatment continually develop.

RECENT FINDINGS

The prevalence of drug resistance has been constantly rising during the recent years. It has peaked in eastern European countries such as Belarus, where a record of 35.5% MDR-TB amongst new cases have been reported from Minsk. New diagnostic tools are becoming available. Xpert MTB/RIF is by far the most promising of these new techniques. Clinical management of drug-resistant TB is still cumbersome. However, after over 40 years of neglect, new drugs are becoming readily available: delamanid, bedaquiline, and PA-824 combined into innovative regimens raise hopes for substantially higher success rates.

SUMMARY

The innovative diagnostic tools recently validated are changing the traditional paradigms of TB diagnosis, for too long based on sputum smear, culture, and drug susceptibility testing. New anti-TB compounds, which can be combined with several 'old' drugs with new indications, are gradually modifying the chances of cure for MDR-TB cases. Although initial evidence appears promising, the market use of new drugs must be accompanied by a serious public health approach aimed at preventing the development of further drug resistance.

A simple and efficient multiplex PCR assay for the identification of Mycobacterium genus and Mycobacterium tuberculosis complex to the species level

PURPOSE

The Mycobacterium tuberculosis complex comprises M. tuberculosis, M. bovis, M. bovis bacillus Calmette-Guérin (BCG) and M. africanum, and causes tuberculosis in humans and animals. Identification of Mycobacterium spp. and M. tuberculosis complex to the species level is important for practical use in microbiological laboratories, in addition to optimal treatment and public health.

MATERIALS AND METHODS

A novel multiplex PCR assay targeting a conserved rpoB sequence in Mycobacteria spp., as well as regions of difference (RD) 1 and RD8, was developed and evaluated using 37 reference strains and 178 clinical isolates.

RESULTS

All mycobacterial strains produced a 518-bp product (rpoB), while other bacteria produced no product. Virulent M. tuberculosis complex strains, M. tuberculosis, M. bovis and M. africanum, produced a 254-bp product (RD1), while M. bovis BCG, M. microti and nontuberculous mycobacteria produced no RD1 region product. Additionally, M. tuberculosis and M. africanum produced a 150-bp product (RD8), while M. bovis and M. bovis BCG produced a 360-bp product (deleted form of RD8). M. microti and nontuberculous mycobacteria produced no RD8 region product. This assay identified all Mycobacterium spp. and all M. tuberculosis complex strains to the species level.

CONCLUSION

The multiplex PCR assay of the present study could be implemented as a routine test in microbiology laboratories, and may contribute to more effective treatment and surveillance of tuberculosis stemming from the M. tuberculosis complex.

A medicinal chemists' guide to the unique difficulties of lead optimization for tuberculosis

Tuberculosis is a bacterial disease that predominantly affects the lungs and results in extensive tissue pathology. This pathology contributes to the complexity of drug development as it presents discrete microenvironments within which the bacterium resides, often under conditions where replication is limited and intrinsic drug susceptibility is low. This consolidated pathology also results in impaired vascularization that limits access of potential lead molecules to the site of infection. Translating these considerations into a target-product profile to guide lead optimization programs involves implementing unique in vitro and in vivo assays to maximize the likelihood of developing clinically meaningful candidates.

Tuberculous meningitis: more questions, still too few answers

Tuberculous meningitis is especially common in young children and people with untreated HIV infection, and it kills or disables roughly half of everyone affected. Childhood disease can be prevented by vaccination and by giving prophylactic isoniazid to children exposed to infectious adults, although improvements in worldwide tuberculosis control would lead to more effective prevention. Diagnosis is difficult because clinical features are non-specific and laboratory tests are insensitive, and treatment delay is the strongest risk factor for death. Large doses of rifampicin and fluoroquinolones might improve outcome, and the beneficial effect of adjunctive corticosteroids on survival might be augmented by aspirin and could be predicted by screening for a polymorphism in LTA4H, which encodes an enzyme involved in eicosanoid synthesis. However, these advances are insufficient in the face of drug-resistant tuberculosis and HIV co-infection. Many questions remain about the best approaches to prevent, diagnose, and treat tuberculous meningitis, and there are still too few answers.

Can combination prevention strategies reduce HIV transmission in generalized epidemic settings in Africa? The HPTN 071 (PopART) study plan in South Africa and Zambia

The HIV Prevention Trials Network (HPTN) is conducting the HPTN 071 (PopART) study in 21 communities in Zambia and South Africa with support from a consortium of funders. HPTN 071 (PopART) is a community-randomized trial of a combination prevention strategy to reduce HIV incidence in the context of the generalized epidemic of southern Africa. The full PopART intervention strategy is anchored in home-based HIV testing and facilitated linkage of HIV-infected persons to care through community health workers and universal antiretroviral therapy for seropositive persons regardless of CD4+ cell count or HIV viral load. To further reduce the risk of HIV acquisition among uninfected individuals, the study aims to expand voluntary medical male circumcision, diagnosis and treatment of sexually transmitted infections, behavioral counseling, and condom distribution. The full PopART intervention strategy also incorporates promotion of other interventions designed to reduce HIV and tuberculosis transmission, including optimization of the prevention of mother-to-child HIV transmission and enhanced individual and public health tuberculosis services. Success for the PopART strategy depends on the ability to increase coverage for the study interventions whose uptake is a necessary antecedent to a prevention effect. Processes will be measured to assess the degree of penetration of the interventions into the communities. A randomly sampled population cohort from each community will be used to measure the impact of the PopART strategy on HIV incidence over 3 years. We describe the strategy being tested and progress to date in the HPTN 071 (PopART) study.

Diagnosis, treatment and prevention of tuberculosis in children

In Australia, tuberculosis notification rates have plateaued at a low level and disease is highly concentrated in immigrant communities where children may be affected. Many clinicians regard tuberculosis as an adult disease, hence it is rarely considered in the differential diagnosis of sick children. This paper provides a brief overview of the natural history of the disease in children to demonstrate the importance of taking a careful tuberculosis exposure history. It also provides guidance regarding the diagnosis, treatment and prevention of tuberculosis in children. The management of paediatric cases is not difficult if important differences with adult disease are carefully considered; these differences are discussed in detail.

Multidrug-resistant Tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) threatens to become the dominant form of tuberculosis in many parts of the world because of decades of inappropriate treatment on a global scale. Infection with MDR-TB is associated with poor outcomes because of delays in treatment and the need for complex, toxic, and long medication regimens. Most cases are undetected because of technological and economic barriers to diagnosing tuberculosis and the availability of assays to test for drug resistance. Experience in treating MDR-TB is scarce. Tuberculosis was once curable, but could become a potentially untreatable infectious disease unless efforts are made to control it.

Assessment of the sensitivity and specificity of Xpert MTB/RIF assay as an early sputum biomarker of response to tuberculosis treatment

BACKGROUND

An accurate biomarker is urgently needed to monitor the response to treatment in patients with pulmonary tuberculosis. The Xpert MTB/RIF assay is a commercially available real-time PCR that can be used to detect Mycobacterium-tuberculosis-specific DNA sequences in sputum samples. We therefore evaluated this assay with serial sputum samples obtained over 26 weeks from patients undergoing treatment for tuberculosis.

METHODS

We analysed sputum samples from 221 patients with smear-positive tuberculosis enrolled at two sites (Cape Town, South Africa, and Mbeya, Tanzania) of a multicentre randomised clinical trial REMoxTB of antituberculosis treatment on a weekly basis (weeks 0 to 8), then at weeks 12, 17, 22, and 26 after treatment initiation. The Xpert MTB/RIF results over time were compared with the results of standard smear microscopy and culture methods.

FINDINGS

We obtained and analysed 2741 sputum samples from 221 patients. The reduction in positivity rates with Xpert MTB/RIF were slower than those with the standard methods. At week 8, positive results were obtained for 62 (29%) of 212 sputum samples with smear microscopy, 46 (26%) of 175 with solid culture (Löwenstein-Jensen medium), 77 (42%) of 183 with liquid culture (Bactec MGIT960 system), and 174 (84%) of 207 with Xpert MTB/RIF; at 26 weeks, positive results were obtained for ten (5%) of 199, four (3%) of 157, seven (4%) of 169, and 22 (27%) of 83 sputum samples, respectively. The reduction in detection of quantitative M tuberculosis DNA with Xpert MTB/RIF correlated with smear grades (ρ=-0·74; p<0·0001), solid culture grades (ρ=-0·73; p<0·0001), and time to liquid culture positivity (ρ=0·73; p<0·0001). Compared with the combined binary smear and culture results as a reference standard, the Xpert MTB/RIF assay had high sensitivity (97·0%, 95% CI 95·8-97·9), but poor specificity (48·6%, 45·0-52·2).

INTERPRETATION

The poor specificity precludes the use of the Xpert MTB/RIF assay as a biomarker for monitoring tuberculosis treatment, and should not replace standard smear microscopy and culture.

FUNDING

Global Alliance for TB Drug Development, Bill & Melinda Gates Foundation, UK Medical Research Council, German Ministry of Science and Technology.

Advances in the development of new tuberculosis drugs and treatment regimens

Despite the introduction 40 years ago of the inexpensive and effective four-drug (isoniazid, rifampicin, pyrazinamide and ethambutol) treatment regimen, tuberculosis (TB) continues to cause considerable morbidity and mortality worldwide. For the first time since the 1960s, new and novel drugs and regimens for all forms of TB are emerging. Such regimens are likely to utilize both repurposed drugs and new chemical entities, and several of these regimens are now progressing through clinical trials. This article covers current concepts and recent advances in TB drug discovery and development, including an update of ongoing TB treatment trials, newer clinical trial designs, TB biomarkers and adjunct host-directed therapies.

Transmission of multidrug-resistant tuberculosis in the USA: a cross-sectional study

BACKGROUND

Multidrug-resistant (MDR) tuberculosis is a potential threat to tuberculosis elimination, but the extent of MDR tuberculosis disease in the USA that is attributable to transmission within the country is unknown. We assessed transmission of MDR tuberculosis and potential contributing factors in the USA.

METHODS

In a cross-sectional study, clinical, demographic, epidemiological, and Mycobacterium tuberculosis genotype data were obtained during routine surveillance of all verified cases of MDR tuberculosis reported from eight states in the USA (California from Jan 1, 2007, to Dec 31, 2009; Texas from Jan 1, 2007, to March 31, 2009; and the states of Colorado, Maryland, Massachusetts, New York, Tennessee, and Washington from Jan 1, 2007 to Dec 31, 2008). In-depth interviews and health-record abstraction were done for all who consented to ascertain potential interpersonal connections.

FINDINGS

168 cases of MDR tuberculosis were reported in the eight states during our study period. 92 individuals (55%) consented to in-depth interview. 20 (22%) of these individuals developed MDR tuberculosis as a result of transmission in the USA; a source case was identified for eight of them (9%). 20 individuals (22%) had imported active tuberculosis (ie, culture-confirmed disease within 3 months of entry into the USA). 38 (41%) were deemed to have reactivation of disease, of whom 14 (15%) had a known previous episode of tuberculosis outside the USA. Five individuals (5%) had documented treatment of a previous episode in the USA, and so were deemed to have relapsed. For nine cases (10%), insufficient evidence was available to definitively classify reason for presentation.

INTERPRETATION

About a fifth of cases of MDR tuberculosis in the USA can be linked to transmission within the country. Many individuals acquire MDR tuberculosis before entry into the USA. MDR tuberculosis needs to be diagnosed rapidly to reduce potential infectious periods, and clinicians should consider latent tuberculosis infection treatment-tailored to the results of drug susceptibility testing of the putative source case-for exposed individuals.

FUNDING

Centers for Disease Control and Prevention.