Drug resistance refers to the ability of a microorganism, such as bacteria or viruses, to withstand the effects of drugs that are designed to kill them. This can occur when these organisms evolve and adapt in response to exposure to medications, leading to changes in their cellular structure or metabolic processes that allow them to survive despite being exposed to drug treatments. Drug resistance is a significant concern for public health because it can render certain drugs less effective or even completely ineffective in treating infections caused by these resistant organisms, making it more difficult and expensive to treat patients with such conditions.