The ability of an organism to resist the action of an inhibitory molecule or compound. Examples of drug resistance include disease-causing bacteria evading the activity of antibiotics, the human immunodeficiency virus resisting antiviral agents, and human cancer cells replicating despite the presence of chemotherapy agents. There are many ways in which cells or organisms become resistant to drugs, and some organisms have developed many resistance mechanisms, each specific to a different drug. Drug resistance is best understood as it applies to bacteria, and the increasing resistance of many common disease-causing bacteria to antibiotics is a global crisis.