The Tuberculosis Pipeline Introduction
Multi-drug resistant (MDR) and Extensively drug-resistant (XDR) TB Over the past 62 years, MTB has been exposed to single and multiple chemotherapy regimens, allowing MTB strains to evolve when treatment is inadequate, incomplete, intermittent, or inappropriate. Failure to properly treat drug-susceptible TB leads to the emergence of circulating strains of drug resistant TB. Multidrug-resistant (MDRTB) and extensively drug-resistant TB (XDR-TB) are two types of drug-resistant TB strains defined by the number and types of drugs the TB bacilli are resistant to. MDR-TB is TB bacteria that are resistant to two of the most powerful first-line drugs, isoniazid and rifampicin. XDR-TB is TB bacteria that are resistant to any of the fluoroquinolone drugs (cipro-, gatiflox-, levo-, moxiflox-, or ofloxacin) and any one of the three second-line injectables (amikacin, capreomycin, or kanamycin), as well as isoniazid and rifampicin. Inadequate health and TB control systems facilitate the creation of drug resistant TB because they fail to properly treat drug-susceptible TB. Treatment for drug-susceptible TB normally involves a 6-8 month treatment regimen using four oral TB drugs, but patients regularly face adherence obstacles due to the high pill burden, drug-to-drug interactions, toxic side effects, drug stock outs and/or length of treatment. Consequently, when treatment is inconsistent, inadequate, or interrupted, the TB bacteria begin to mutate, develop resistance to the anti-TB medication, multiply and make the individual sick again. Treatment for drug-resistant TB is complex and expensive. Diagnosis of MDR or XDR-TB requires sophisticated diagnostic tools, technicians and laboratory capacity, which are limited or non-existent in resource poor regions that need it most. The World Health Organization (WHO) estimates there were 500,000 new cases of MDR-TB in 2007—the highest number of MDR cases ever reported—of which only 30,000 cases were confirmed, and a mere 1% were started on treatment (WHO 2009a).
TB Diagnostics, Prevention, Treatment and Care Challenges Sputum smear microscopy, the most commonly used TB diagnostic tool, is over 125 years old. The test involves collecting a sputum sample coughed up from the lungs of a patient suspected of having TB, staining the sample, and identifying the rod-like shaped MTB bacteria under a microscope. Smear-positive TB is a diagnosis confirming the presence of actively replicating TB bacteria in the lungs. Unfortunately, the sputum smear test is not very accurate and at best captures 62% of new smear positive
103