Pub. date: 2008 | Online Pub. Date: April 21, 2008 | DOI: 10.4135/9781412963855 | Print ISBN: 9781412941860 | Online ISBN: 9781412963855| Publisher:SAGE Publications, Inc.About this encyclopedia
Bacterial infections occur when single-celled microorganisms called bacteria colonize the human body. While this colonization is usually fended off by the immune system, bacteria cause disease when they cannot be controlled and begin to interfere with normal function. Bacteria can invade almost any system of the body, and do so through many routes of entry. Some types of bacteria normally live symbiotically with humans, especially on the skin and in the gut, but these can cause disease when they grow out of control or enter parts of the body where they are not normally found. There are millions of different species of bacteria, but only a handful account for the majority of infections in humans. It is difficult to quantify exactly how much disease is caused by bacterial infections, but it is significant. In 2002, lower respiratory infections and diarrheal diseases, which are usually caused by bacteria, were the Some ...