Global Impact of Multidrug-Resistant Pulmonary Tuberculosis Among HIV-Infected and Other Immunocompromised Hosts: Epidemiology, Diagnosis, and Strategies for Management

Molecular Diagnosis of TB in the HIV Positive Population

BACKGROUND

Tuberculosis (TB) remains a major contributor to morbidity and mortality in HIV-positive individuals, causing 1.1 million incident cases and 0.32 million deaths in 2012. Diagnosis of TB is particularly challenging in HIV-coinfected individuals, due to a high frequency of smear-negative disease, atypical presentations, and extrapulmonary TB.

OBJECTIVE

The aim of this article was to review the current literature on molecular diagnostics for TB with an emphasis on the performance of these diagnostic tests in the HIV-positive population.

METHODS

We searched the PubMed database using at least one of the terms TB, HIV, diagnostics, Xpert MTB/RIF, nucleic acid amplification tests, drug susceptibility testing, RNA transcription, and drew on World Health Organization publications.

FINDINGS

With increased focus on reducing TB prevalence worldwide, a new set of tools for diagnosing the disease have emerged. Molecular tools such as Xpert MTB/RIF and line-probe assays are now in use or are being rolled out in many regions. The diagnostic performance of these and other molecular assays are discussed here as they pertain to the HIV-positive population.

CONCLUSIONS

Molecular diagnostics offer a useful addition and at times, alternative, to traditional culture methods for the diagnosis of TB. However, most of these tests suffer from decreased accuracy in the HIV-positive population.

Tuberculosis therapy for 2016 and beyond

INTRODUCTION

Tuberculosis has been and remains arguably the most important infectious disease of all time. However, when compared to other diseases of similar human impact, relatively little progress has been made. Although there are many new drugs being developed for the first time in decades, it is unclear what role each of these new drugs will play.

AREAS COVERED

The history of current therapy is reviewed as are the challenges associated with medications currently in use. Drugs that have recently been added to the armamentarium of therapy are reviewed as well as new candidate drugs.

EXPERT OPINION

Developing new drugs to treat tuberculosis is of critical importance but even more important is developing strategies that ensure that there is no further amplification of drug resistance around the world especially in high burden low resource settings. Directly observed therapy is the cornerstone of protecting existing and future regimens and new technologies will potentially extend the reach of monitored therapy. Challenges remain including maintaining an adequate drug supply but the greatest challenge may be the issue of persistent organisms that require prolonged therapy. By discovering the triggers of persistence and identifying new drug targets can it be possible to radically shorten therapy.

Improved survival in multidrug-resistant tuberculosis patients receiving integrated tuberculosis and antiretroviral treatment in the SAPiT Trial

BACKGROUND

The therapeutic effects of antiretroviral treatment (ART) in patients with multidrug-resistant tuberculosis (MDR-TB) and human immunodeficiency virus (HIV) infection have not been established.

OBJECTIVE

To assess therapeutic outcomes of integrating ART with treatment for MDR-TB.

DESIGN

A subgroup of MDR-TB patients from a randomised controlled trial, the SAPiT (Starting Antiretroviral Therapy at Three Points in Tuberculosis) study, conducted in an out-patient clinic in Durban, South Africa, from 2008 to 2012.

METHODS

Clinical outcomes at 18 months were compared in patients randomised to receive ART within 12 weeks of initiating standard first-line anti-tuberculosis treatment with those who commenced ART after completing anti-tuberculosis treatment.

RESULTS

Mycobacterium tuberculosis drug susceptibility results were available in 489 (76%) of 642 SAPiT patients: 23 had MDR-TB, 14 in the integrated treatment arm and 9 in the sequential treatment arm. At 18 months, the mortality rate was 11.9/100 person-years (py; 95%CI 1.4-42.8) in the combined integrated treatment arm and 56.0/100 py (95%CI 18.2-130.8) in the sequential treatment arm (hazard ratio adjusted for baseline CD4 count and whether MDR-TB treatment was initiated: 0.14; 95%CI 0.02-0.94, P = 0.04).

CONCLUSION

Despite the small sample size, the 86% reduction in mortality due to early initiation of ART in MDR-TB patients was statistically significant.

Current status and future trends in the diagnosis and treatment of drug-susceptible and multidrug-resistant tuberculosis

The global burden of tuberculosis (TB) is still large. The increasing incidence of drug-resistant, multidrug-resistant (MDR) (resistant to at least rifampicin and isoniazid), and extensively drug-resistant (XDR) (additionally resistant to a fluoroquinolone and kanamycin/amikacin/capreomycin) strains of Mycobacterium tuberculosis and the association of active disease with human immunodeficiency virus coinfection pose a major threat to TB control efforts. The rapid detection of M. tuberculosis strains and drug susceptibility testing (DST) for anti-TB drugs ensure the provision of effective treatment. Rapid molecular diagnostic and DST methods have been developed recently. Treatment of drug-susceptible TB is effective in ≥95% of disease cases; however, supervised therapy for ≥6 months is challenging. Non-adherence to treatment often results in the evolution of drug-resistant strains of M. tuberculosis due to mutations in the genes encoding drug targets. Sequential accumulation of mutations results in the evolution of MDR and XDR strains of M. tuberculosis. Effective treatment of MDR-TB involves therapy with 5-7 less effective, expensive, and toxic second-line and third-line drugs for ≥24 months and is difficult in most developing countries. XDR-TB is generally an untreatable disease in developing countries. Some currently existing drugs and several new drugs with novel modes of action are in various stages of development to shorten the treatment duration of drug-susceptible TB and to improve the outcome of MDR-TB and XDR-TB.

Central nervous system infections in travelers

International travelers commonly contract infections while abroad, many of which are primary neurological diseases or have potential neurological sequelae. The implications of these neuroinfectious diseases extend beyond the individual, since returning travelers may contribute to the spread of infection in novel areas. In this review, we discuss signs, symptoms, treatments, and prophylaxes for these infections, as well as emerging trends with regard to neuroinfectious diseases of the returning traveler.

Dipterinyl calcium pentahydrate inhibits intracellular mycobacterial growth in human monocytes via the C-C chemokine MIP-1β and nitric oxide

Tuberculosis remains one of the top three leading causes of morbidity and mortality worldwide, complicated by the emergence of drug-resistant Mycobacterium tuberculosis strains and high rates of HIV coinfection. It is important to develop new antimycobacterial drugs and immunomodulatory therapeutics and compounds that enhance antituberculous immunity. Dipterinyl calcium pentahydrate (DCP), a calcium-complexed pterin compound, has previously been shown to inhibit human breast cancer cells and hepatitis B virus (HBV). DCP inhibitory effects were attributed to induction of apoptosis and/or increased production of interleukin 12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF). In this study, we tested the ability of DCP to mediate inhibition of intracellular mycobacteria within human monocytes. DCP treatment of infected monocytes resulted in a significant reduction in viability of intracellular but not extracellular Mycobacterium bovis BCG. The antimicrobial activity of DCP was comparable to that of pyrazinamide (PZA), one of the first-line antituberculosis drugs currently used. DCP potentiated monocyte antimycobacterial activity by induction of the cysteine-cysteine (C-C) chemokine macrophage inflammatory protein 1β (MIP-1β) and inducible nitric oxide synthase 2. Addition of human anti-MIP-1β neutralizing antibody or a specific inhibitor of the l-arginase-nitric oxide pathway (N(G)-monomethyl l-arginine [l-NMMA] monoacetate) reversed the inhibitory effects of DCP on intracellular mycobacterial growth. These findings indicate that DCP induced mycobacterial killing via MIP-1β- and nitric oxide-dependent effects. Hence, DCP acts as an immunoregulatory compound enhancing the antimycobacterial activity of human monocytes.

Paradoxical Mycobacterium tuberculosis meningitis immune reconstitution inflammatory syndrome in an HIV-infected child

Immune reconstitution inflammatory syndrome occurs in a subset of HIV-infected individuals as the immune system recovers secondary to antiretroviral therapy. An exaggerated and uncontrolled inflammatory response to antigens of viable or nonviable organisms is characteristic, with clinical deterioration despite improvement in laboratory indicators. We describe a fatal case of Mycobacterium tuberculosis meningitis immune reconstitution inflammatory syndrome in an HIV-infected child and review the literature.

Antituberculosis therapy for 2012 and beyond

INTRODUCTION

In terms of human suffering, tuberculosis has a huge impact on global society, making it arguably the most important infectious disease in history. Despite the devastating impact on society, the tools to fight tuberculosis are very limited. Current standard therapy has been used for over 40 years and threats, such as the HIV epidemic and drug-resistant strains, undermine efforts to control the disease. New drugs are needed to address the challenges faced globally.

AREAS COVERED

Current therapy is briefly reviewed in this paper and then new doses and combinations of existing drugs are presented. New candidate drugs are also discussed, along with the potential benefits and pitfalls of each of the compounds and approaches to therapy.

EXPERT OPINION

Despite the need to develop new drugs, the ability of programs to deliver existing therapies must not be neglected. Directly observed therapy and a standard basic level of care for all patients with tuberculosis, regardless of where they reside, is imperative, and will ensure that new drugs and regimens will have the greatest possible impact. New combination regimens, including PA 824 and TMC207, in combination with existing drugs, are very exciting - not only because of their ability to shorten treatment regimens in pan-susceptible cases, but also because they can be used among drug-resistant strains. Although an effective vaccine will probably be necessary to eliminate tuberculosis, new drugs and combination regimens have the potential to save millions of lives before tuberculosis is finally eliminated.

Tuberculosis of the central nervous system in immunocompromised patients: HIV infection and solid organ transplant recipients

Central nervous system (CNS) tuberculosis (TB) is a devastating infection with high rates of morbidity and mortality worldwide and may manifest as meningitis, tuberculoma, abscess, or other forms of disease. Immunosuppression, due to either human immunodeficiency virus infection or solid organ transplantation, increases susceptibility for acquiring or reactivating TB and complicates the management of underlying immunosuppression and CNS TB infection. This article reviews how immunosuppression alters the clinical presentation, diagnosis, treatment, and outcome of TB infections of the CNS.