XDR Tuberculosis — Implications for Global Public Health

Abstract

In early 2005, physicians at a rural hospital in KwaZulu-Natal, a province of South Africa, were concerned by a high rate of rapid death among patients infected with the human immunodeficiency virus (HIV) who also had tuberculosis. A study revealed the presence not only of multidrug-resistant (MDR) tuberculosis but also what came to be called extensively drug-resistant (XDR) tuberculosis. XDR tuberculosis is caused by a strain of Mycobacterium tuberculosis resistant to isoniazid and rifampin (which defines MDR tuberculosis) in addition to any fluoroquinolone and at least one of the three following injectable drugs: capreomycin, kanamycin, and amikacin. Of 53 patients with XDR tuberculosis, 55% claimed they had never been treated (implying that they had primary infection with an XDR strain of M. tuberculosis); two thirds had recently been hospitalized; and all 44 who underwent testing were HIV-positive. All but one of the patients died of tuberculosis, with a median survival period of only 16 days from the time the first sputum specimen was collected. Genotyping analysis revealed that 85% of the 46 isolates tested belonged to the KwaZulu-Natal (KZN) family of tuberculosis strains, which had been recognized in the province for a decade.¹