Antibiotics are antimicrobial drugs that are effective against bacteria. They treat infections caused by bacteria by either killing the bacteria or preventing them from reproducing. While most bacteria in the human body are harmless and even beneficial, there are several types of pathogenic bacteria that cause various types of infections including strep throat, sinus, ear, respiratory tract, and urinary tract infections. Some bacterial infections can be life threatening. Antibiotics are integral to treating these infections and saving lives.