Table 2. Description of acquired drug resistance profiles used to categorize resistance to anti-TB drugs*.

Acquired drug resistance profile	Description of drug-resistance profile
TB patients who did not have MDR TB before or after acquiring resistance	Initially sensitive to isoniazid, rifampin, or both and may have acquired resistance to either isoniazid or rifampin but not both or may have acquired resistance to other anti-TB drug(s).
TB patients who acquired resistance that resulted in MDR TB	Initially sensitive to isoniazid, rifampin, or both and acquired resistance to isoniazid, rifampin, or both to have MDR TB.
Patients with initial MDR TB and acquired resistance to additional drugs	Initially resistant to at least isoniazid and rifampin and on subsequent culture acquired resistance to other anti-TB drug(s).

*MDR, multidrug-resistant; TB, tuberculosis.