Mycobacterial Infections

The current issue of Seminars in Respiratory and Critical Care Medicine reviews the broad spectrum of diseases caused by mycobacterial infections, including Mycobacterium tuberculosis and nontuberculous mycobacteria (NTM). The first six articles provide in-depth reviews of tuberculosis, highlighting the changing epidemiology, advances in diagnosis, and treatment of both tuberculosis (TB) and latent tuberculosis infection (LTBI). The last seven articles focus on topics related to NTM infections, such as the human and environmental epidemiology and the diagnosis and treatment of NTM infections.

Each year ∼ 9 million new TB cases are reported to health departments around the world. Glaziou and colleagues from the World Health Organization (WHO) have provided a detailed review of the global epidemiology of TB and offer hope as to how to achieve global elimination of TB by 2050. Because new diagnostic tools will be needed to achieve these ambitious goals Boehme et al review the remarkable advances in the laboratory approach to the diagnosis of TB and provide a glimpse of the future of TB diagnostics. Rapid diagnosis is particularly important in individuals coinfected with human immunodeficiency virus (HIV) and those with multidrug resistant tuberculosis (MDR-TB). As reviewed by Gray and Cohn, management of HIV/TB coinfection is complex; however, recent studies have documented improved outcomes when HIV-infected patients with TB are started on antiretroviral drugs early in the course of their therapy. Management of MDR-TB is also complex and associated with less than optimum treatment outcomes. Daley and Caminero review the approach to management of MDR-TB based on the recent WHO updated guidelines. Although diagnosis and treatment of active TB remain the most important goals in TB control programs, identification of LTBI and treatment are critical elements in the path toward TB elimination. Recent advances in the diagnosis and treatment of LTBI are reviewed in detail by Schluger and Vernon, respectively.

NTM comprise over 150 species, and the frequency of disease caused by these organisms is on the rise. Kendall and Winthrop have provided an excellent update on the epidemiology of these increasingly important pathogens. The reasons for the increase are not known, but more frequent environmental exposures and increased host susceptibility have been postulated. To address the first issue, Falkinham reviews the environmental ecology of NTM, documenting instances in which environmental exposure to NTM has led to human disease. Chan and Iseman review our understanding of the pathogenesis of NTM pulmonary infections and describe populations at increased risk of developing pulmonary NTM disease. Because of the increasing importance of NTM infections, it is critical for clinicians to understand current diagnostic tests, including drug-susceptibility testing methods. Therefore, van Ingen provides a concise review of current laboratory procedures used for the diagnosis of NTM disease. Philley and Griffith provide a practical review of current management strategies for the more common NTM species, whereas Leung and Olivier focus on NTM infections in patients with cystic fibrosis. Finally, Kasperbauer and Huitt review the ever-challenging management of extrapulmonary infections caused by NTM.

In summary, this issue of Seminars will hopefully illustrate the enormous burden of disease caused by mycobacteria as well as the complicated diagnostic and treatment approaches required to manage and prevent these infections. I would like to thank the many contributors to this issue for sharing their extraordinary knowledge and experience, which I hope will enhance the readers' interest and understanding of mycobacterial infections.