Table 1. Initial drug resistance profiles used to categorize resistance to anti-TB drugs*.

Initial drug resistance profile	Description of drug-resistance profile†
Drug sensitive	Initially sensitive to both isoniazid and rifampin
Isoniazid resistance without MDR TB	Initially resistant to isoniazid and sensitive to rifampin
Rifampin resistance without MDR TB	Initially resistant to rifampin and sensitive to isoniazid
MDR TB	Initially resistant to both isoniazid and rifampin

*MDR, multidrug-resistant; TB, tuberculosis.
†These profiles refer specifically to resistance to isoniazid and/or rifampin, but resistance to other drugs may also be present.