Sometimes the anti-TB drug being taken by the patient can no longer kill the TB bacteria. This is referred to as drug-resistant TB. Drug-resistant TB can occur when the drugs used to treat TB are misused or mismanaged. Examples include: when people do not complete the full course of treatment when health-care providers prescribe the wrong treatment, the wrong dose, or wrong length of time for taking the drugs when the supply of drugs is not always available when the drugs are of poor quality.