E. Coli 0157:H7 (cont.)
Charles Patrick Davis, MD, PhD
Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
In this Article
What is E. coli?
Escherichia coli (E. coli) is a gram-negative bacterium that can survive in an environment with or without air (facultative anaerobe) and, depending on the environment, may or may not produce thin hair-like structures (flagella or pili) that allow the bacteria to move and to attach to human cells. These bacteria commonly live in the intestines of people and animals worldwide.
There are many serotypes or strains (over 700) of E. coli. Most of the E. coli are normal inhabitants of the small intestine and colon and do not cause disease in the intestines. (They are non-pathogenic.) Nevertheless, these non-pathogenic E. coli can cause disease if they spread outside of the intestines, for example, into the urinary tract (where they cause bladder or kidney infections), or into the blood stream (sepsis). Other E. coli strains (enterovirulent E. coli strains or EEC) cause "poisoning" or diarrhea even though they usually remain within the intestine by producing toxins or intestinal inflammation. There are four to six groups (some researchers combine groups) of E. coli serotypes that comprise EEC. Their names are derived from descriptions of the characteristics that separate them from the other groups.
E. coli were first isolated by T. Escherich in 1885 and were named after him. The over 700 serotypes are identified by small antigenic changes in their surface "O" antigens (lipopolysaccharides or molecules on the bacterial surface of gram-negative bacteria), for example E. coli 0157 or E. coli 055. These serotypes are identified by immunological tests using antibodies to the antigens. E coli strains are further distinguished by "H" protein antigens (different types of flagella that make the bacteria motile). Consequently, a particular E. coli strain can be identified as H, followed by a number, and this identifier is added to the "O" name; for example, E. coli 0157:H7. Although this name designation seems complicated, researchers and clinicians use these antigenic identifiers to track specific E. coli strains that cause outbreaks of disease.
As discussed previously, E. coli strain, E. coli 0157:H7 is notorious for its potential to cause complicated disease in humans; the remainder of this article will focus on this E. coli strain. However, it is important to remember other types of E. coli produce similar if not identical problems and they too, will be addressed in this article; the newest serotype causing problems is E. coli 0145.
Reviewed by Jay W. Marks, MD on 6/20/2012
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