Drug-Resistant Tuberculosis Increasing From Use of Second-Line Drugs

March 23, 2007 — The March 23 issue of the Morbidity and Mortality Weekly Report (MMWR) describes 1993-2006 trends in extensively drug-resistant tuberculosis and in tuberculosis incidence in the United States."The worldwide emergence of extensively drug-resistant tuberculosis (XDR TB) and a provisional definition for this form of TB were first reported in November 2005," write N. S. Shah, MD, from Albert Einstein College of Medicine in Bronx, New York, and colleagues. "XDR TB presents a global threat and a challenge to TB-control activities in the United States. To prevent the spread of XDR TB, renewed vigilance is needed through drug-susceptibility testing, case reporting, specialized care, infection control, and expanded capacity for outbreak detection and response." The Emergency Global Task Force on XDR TB, convened by the World Health Organization in October 2006, revised the case definition to specify resistance to at least isoniazid and rifampin among first-line anti-TB drugs, resistance to any fluoroquinolone, and resistance to at least one second-line injectable drug (amikacin, capreomycin, or kanamycin).Using the revised case definition and provisional data for 2006, this report updates the 2006 report on XDR TB in the United States. The investigators analyzed US National TB Surveillance System (NTSS) data for reported XDR-TB cases from 50 states and the District of Columbia (DC) during 1993 to 2006. All culture-confirmed cases with initial drug-susceptibility test (DST) results reported for at least isoniazid and rifampin were included in the analysis.Of 49 cases (3% of evaluable multidrug-resistant [MDR] TB cases) meeting the revised case definition for XDR TB, 17 (35%) were reported during 2000 to 2006. Compared with cases identified during surveillance from 1993 to 1999, those from 2000 to 2006 were more likely to be in foreign-born persons and less likely to be in persons infected with human immunodeficiency virus (HIV). Of 202,436 culture-confirmed TB cases reported to NTSS during 1993 to 2006, 190,312 had initial DST results for at least isoniazid and rifampin, including 2927 cases (2%) with initial resistance to both drugs (MDR TB). Of 1665 (57%) of 2927 MDR-TB cases that had DST results reported for at least one fluoroquinolone and one injectable second-line drug, 49 cases (3%) met the revised definition of XDR TB, including 32 cases reported during 1993 to 1999 and 17 cases during 2000 to 2006. The 49 XDR-TB cases were reported from 9 states and 1 city, with the largest numbers reported from New York City (19 cases) and California (11 cases). Of 29 cases (59% of the 49 persons with XDR TB) for which HIV status was known, 16 (55%) were HIV-positive. Of 19 persons with XDR TB with known HIV status during 1993 to 1999, 14 (74%) were HIV-positive. Of 10 persons with known HIV status during 2000 to 2006, 2 (20%) were HIV-positive