Overuse and misuse of antibiotics are the main culprits. Antibiotics are often taken when not needed, such as for viral illnesses like the common cold, or stopped midway through a treatment course. In some regions, antibiotics can even be purchased without a prescription, which makes self-medication dangerously common.
But that’s not the full picture. Antibiotics are also used heavily in livestock and agriculture to promote growth and prevent disease in animals. This overuse in animals seeps into the environment and food chain, giving bacteria more opportunities to develop resistance.
Even poor sanitation, contaminated water, and improper waste disposal play a part by allowing resistant bacteria to spread more easily.