Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.Because over time they kill off weaker bacteria, and the stronger bacteria still live. when the stronger bacteria live, they multiply, creating stronger bacteria. so if the bacteria are stronger, people get sicker, and the antibiotics no longer kill the strong bacteria. creating a superbug, that is a super illness.