Pathogenic bacteria that have become resistant to antibiotic therapy are an increasing public health problem. For example, tuberculosis, gonorrhea, malaria, and ear infections in children are just a few of the diseases that have become hard to treat with antibiotic drugs. Part of the problem is that microorganisms that cause infections are extremely hardy and can develop ways to endure drugs meant to kill or weaken them. This antibiotic resistance (antimicrobial resistance or drug resistance), is due largely to the increasing use of antibiotics. Ironically, antimicrobial resistance has been recognized since the introduction of penicillin nearly 50 years ago, when penicillin-resistant infections caused by Staphylococcus aureus rapidly appeared.