RESUMEN
SETTING: An out-patient methadone treatment program MTP). OBJECTIVE: To investigate transmission of multidrug-resistant tuberculosis (MDR-TB) in the MTP. DESIGN: Cases were defined as MTP clients or staff who developed TB between 1 January 1994 and 1 January 1996, with at least one positive culture for Mycobacterium tuberculosis resistant to isoniazid and rifampin. Contacts were identified, located and evaluated. RESULTS: Thirteen cases of MDR-TB occurred among 462 clients and staff. One fifth (6/30) of the members of a counseling group for human immunodeficiency virus (HIV) infected clients developed MDR-TB. Individuals known to be HIV positive were at greater risk for TB than those who were HIV negative (RR 5.2, 95%CI 1.2-22.7). Of 449 clients and staff identified as contacts, 393 (87.5%) were located and screened. Among those with a negative baseline tuberculin skin test, 18.5% (56/303) were skin test converters. Attendance at the MTP during a period when the index case was infectious was associated with an increased risk of conversion (RR 2.5, 95%CI 1.1-6.0). CONCLUSION: Extensive transmission of MDR-TB occurred at an out-patient MTP serving numerous clients with HIV infection. This outbreak underscores the importance of developing effective strategies to prevent TB transmission in this setting.