Recent tuberculosis diagnosis toward the end TB strategy

Highlights

• Tuberculosis detections using microbiological, immunological and molecular methods.

• Point-of-care testings (POCTs) for tuberculosis diagnosis using nanomaterials.

• Additional complementary method must be developed for removing false-positives.

Abstract

Tuberculosis (TB) is an infectious bacterial disease caused by Mycobacterium tuberculosis. Despite global TB eradication efforts, it is still a global public health concern, especially in low- and middle-income countries. Most of the active TB infections are curable with early diagnosis and appropriate treatment, but drug-resistant TB is difficult and expensive to treat in immunocompetent as well as immunocompromised individuals. Thus, rapid, economic, and accurate point-of care tools for TB diagnosis are required urgently. This review describes the history of M. tuberculosis detection methods up to date and the recent advances using nanotechnology for point-of-care testing of TB diagnosis.

Introduction

Various types of infectious diseases have occurred throughout human history, killing countless numbers of people. The infectious disease tuberculosis (TB) has existed since the earliest record of human history and has been estimated to have infected humans as early as three million years ago. TB is the second-deadliest infectious disease worldwide; the infection is caused by the bacterium Mycobacterium tuberculosis (World Health Organization, 2014).

Throughout history and even without the ability to diagnose TB, people have made records about TB and its ability to kill. In 1882, Robert Koch discovered that M. tuberculosis is the causative agent of TB and the day he made this declaration to the Berlin Physiological Society, March 24, became the international “World TB Day” (Cambau and Drancourt, 2014). People worldwide became more aware of this disease, which is transmitted from the ill to the healthy through a minute droplet of aerosol that contains M. tuberculosis. The development of scientific equipment, such as X-rays, facilitated the radiographic visualization of changes caused by TB in a healthy person. Further studies in the early 20th century led to an understanding of the etiology and pathological changes of TB, eventually allowing for detection of the organism (Lawn and Zumla, 2011).

The worldwide effort to stop TB has resulted in a cure and led to an increase in survival rate. However, the emergence of the human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS) prevented global TB eradication, and TB remains a global hazard that requires attention. Eventually, TB was declared a “global emergency” by the World Health Organization (WHO) in April 1993 (WHO Global Tuberculosis Programme, 1994). Furthermore, in the late 1990s, a new form of TB appeared known as drug-resistant TB (DR-TB) (Espinal et al., 2000, Pablos-Méndez et al., 1998, Sharma and Mohan, 2004, Sharma and Mohan, 2006). Through the first decade of the 21st century, the emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) (Chiang et al., 2010, Farnia et al., 2010, Sharma and Mohan, 2004, Sharma and Mohan, 2006) still hamper control of TB. Most recently, rare but very dangerous forms of TB, extremely drug-resistant TB (XXDR-TB), super XDR-TB, and totally drug-resistant TB (TDR-TB) have emerged, especially in India and China (Centers for Disease Control and Prevention, 2006, Farnia et al., 2010, Migliori et al., 2007, Parida et al., 2015, Velayati et al., 2009). These drug-resistant TB strains arise owing to improper use of antibiotics in chemotherapy in patients with drug-susceptible TB, poor adherence to anti-TB drugs, and insufficient monitoring of drug resistance (Gandhi et al., 2010a). In 2014, WHO estimated 9.6 million people suffered from TB and 1.5 million people with TB-related deaths internationally, and estimated 480,000 people worldwide developed MDR-TB and 190,000 people died of MDR-TB (World Health Organization, 2015a).

TB is curable in 85% of cases with appropriate treatment, but a global epidemic may occur if MDR- and XDR-TB cannot be diagnosed and treated in a timely manner, particularly in people co-infected with HIV (Frieden et al., 1996, Gandhi et al., 2010b). Thus, rapid and accurate detection of M. tuberculosis and effective treatment is crucial for TB control. However, the current point-of-care (POC) detection tools are neither rapid nor efficient enough to reduce the rate of infection and TB-related deaths and mostly are limited to the active TB infection. Thus, the most effective strategy for detection of TB should be rapid, cost-effective, field-applicable as accurate as possible. Furthermore, it should detect and discriminate active TB as well as DR-TBs to initiate effective treatment in resource-constrained settings.

This review focuses on the currently available detection methods of TB and highlights the steps for TB eradication by effective TB detection.