Drug-resistant tuberculosis: latest advances.

At the start of 2012, a report from Mumbai, India, that described patients with strains of tuberculosis deemed resistant to all antituberculosis drugs set in motion an eventful year for this disease. What was referred to as totally drug-resistant tuberculosis attracted intense media attention and much debate among health professionals worldwide. Experts convened in March, 2012, by WHO to discuss the global implications of this situation agreed that such cases pose a formidable challenge to public health and point to widespread weaknesses in tuberculosis care. However, revisions of defi nitions were not recommended in view of an absence of standardised methods to test for susceptibility to several of the existing antituberculosis drugs. Furthermore, the paucity of data for optimum treatment regimens in patients with such advanced patterns of drug resistance precluded revisions to current approaches to treatment. Improvements in the accuracy of drug susceptibility testing and the imminent release of new antituberculosis drugs should allow changes in the near future. In response to the identifi cation of this event, the Indian Government has taken a number of bold steps to strengthen laboratory and hospital facilities, improve contact tracing, and tighten regulations on private sales of antituberculosis drugs and unreliable serological diagnostics. A web-based system was created to enable the nationwide collection of notifi cation data on tuberculosis, which, in May, 2012, became mandatorily notifi able. In early 2012, WHO released its latest global roundup on multidrug-resistant tuberculosis (defi ned as resistance to, at least, rifampicin and isoniazid). The highest frequencies of multidrug-resistant tuberculosis ever reported were documented in recent years. Worldwide, about 3% of new and 20% of previously treated patients with tuberculosis have multidrugresistant tuberculosis, with much higher levels in eastern Europe and central Asia than in other regions (appendix). In Belarus, for instance, 35% of new patients with tuberculosis in the capital Minsk have multidrug-resistant tuberculosis. About 9% of patients with multidrug-resistant tuberculosis have strains resistant to a fl uoroquinolone and a second-line injectable drug as well (defi ned as extensively drugresistant tuberculosis). 84 countries have now reported at least one extensively drug-resistant tuberculosis case. Molecular technology has fi nally emerged to improve approaches to tuberculosis diagnosis, which had stagnated during much of the past century. The extent and speed with which one of these molecular assays— Xpert MTB/RIF—has been implemented in low-resource settings is impressive. Within 2 years of its endorsement for use by WHO, this test is now making a diff erence in more than 70 low-income or middle-income countries in the diagnosis of patients with tuberculosis and in the detection of mutations known to confer rifampicin resistance. Results from an updated meta-analysis of 18 studies including 9166 specimens from patients with tuberculosis supported its diagnostic accuracy, including for rifampicin resistance (pooled sensitivity and specifi city in patients with pulmonary tuberculosis in seven studies were 94·1% [95% CI 91·6–96·0] and 97·0% [96·0–97·7], respectively). If these encouraging advances in diagnostics are to make a diff erence to patients with multidrug-resistant tuberculosis, curative treatment needs to be accessible. Treatment for multidrug-resistant tuberculosis is at best long, toxic, and expensive, and is ultimately less eff ective than regimens used to treat drug-susceptible tuberculosis. The largest individual patient data meta-analysis for outcomes of multidrug-resistant tuberculosis, including results from 9153 patients in 23 countries, showed that treatment was successful in an average of 54% of patients overall, whereas 15% of patients died. This article informed the latest WHO guidelines on multidrug-resistant tuberculosis regimens, which recommend the inclusion of pyrazinamide, a later-generation fl uoroquinolone, an injectable agent (amikacin, kanamycin, or capreomycin), ethionamide (or protionamide), and cycloserine or, if cycloserine cannot be used, aminosalicylic acid. An intensive phase lasting 8 months and—for newly diagnosed patients with multidrug-resistant tuberculosis—a total duration of 20 months is suggested in most cases, and modifi ed according to response to therapy. However, only observational data were available for the review and randomised trials are still needed to optimise treatment regimens. The chances of a lasting cure for patients with drugresistant tuberculosis will not improve dramatically with the medications available. New drugs that can be given Published Online January 14, 2013 http://dx.doi.org/10.1016/ S2213-2600(12)70056-5