Antibiotics have long provided an effective treatment against bacterial infections. The creation of drugs such as penicillin, streptomycin, and tetracycline allowed doctors to treat common bacterial infections that were once debilitating and even fatal. As the use of antibiotics has grown in recent decades, bacteria have developed modes of resistance that have rendered some antibiotics unusable. As these “superbugs” have become more resilient and resistant to treatments, researchers have begun to explore new ways to treat infections. Research has turned to the use of antimicrobial peptides as an alternative to traditional antibiotics in the treatment of drug-resistant bacteria. Antimicrobial peptides, also called defensins, are short chains of amino acids that act against microorganisms. In plants and animals these peptides consist of between 15 and 45 amino acid residues and are usually cationic, meaning they contain larger amounts of lysine and arginine (Hancock and Lehrer 82). Peptides are produced as part of the body's innate immune system and may be continuously present or produced in response to injury and infection. Because antimicrobial peptides are incorporated into innate immunity and are considered part of the body's second line of defense against infections, they are often found in areas that may be in close contact with environmental pathogens. These areas include “the skin, ear, and eyes, on epithelial surfaces, including the tongue, trachea, lungs, and intestines, as well as in the bone marrow and testes” (Hancock and Scott 8856). Antimicrobial peptides fall into two main categories based on the length of the peptide sequences between the cysteine ​​residues, with subfamilies of - and ...... focus of the article ......a?” Nature Reviews Microbiology 3.3 (2005): 238-250. Academic Research Completed. Web.10 April 2014. Ganz, Thomas. "Defensins: Antimicrobial Peptides in Innate Immunity." Nature Reviews Immunology 3.9 (2003): 710-720 . Network. April 10, 2014. Hancock, Robert E. W. and Monisha G. Scott. “The Role of Antimicrobial Peptides in Animal Defenses.” Proceedings of the National Academy of Sciences of the United States of America 16.97 (2000): 8856-8861. . Google Scholar. 10 April 2014. Hancock, Robert E.W. and Robert Lehrer. 10 April 2014. Reddy, K. V. R., R. D. Yedery, and C. Aranha. “Antimicrobial Peptides: Background and Promise.” International Journal of Antimicrobial Agents 24 (2004): 536-547. Google Scholar. Network. April 10 2014.