Treatment outcome of multidrug-resistant tuberculosis

Abstract

Cases of multidrug-resistant tuberculosis (MDRTB), defined as resistance to at least isoniazid and rifampin, increased sharply in the early 1990s [1–3]. The rise in MDRTB was associated with previous treatment for tuberculosis, human immunodeficiency virus (HIV) infection, and in some inner city communities, recently transmitted disease [1,4,5]. Case fatality rates in early outbreak investigations often exceeded 80%, with a median survival of between 4 and 16 weeks [6–11]. Subsequent data documented a substantial decline in the number of new MDRTB cases and improvement in clinical outcomes, even among severely immunocompromised patients [12– 15]. Drug resistant tuberculosis, however, is not a new phenomenon. In fact, almost immediately after the introduction of streptomycin in 1944, streptomycin-resistant Mycobacterium tuberculosis was described [16,17]. Patients who initially had responded to treatment later relapsed as a result of streptomycin-resistant strains. The development of effective therapy followed by drug resistance and clinical failure is a recurrent theme in the history of tuberculosis. This chapter will focus specifically on studies that have provided data on the expected outcome of patients with MDRTB. The treatment of MDRTB in both the industrial and developing world, the pharmacology of second-line antituberculosis chemotherapy and new chemotherapeutic agents and strategies are discussed elsewhere in this volume [18–21].