Biomedical Engineering Reference
In-Depth Information
*Enterobacter
*Escherichia
*Klebsiella
*Morganella
*Proteus
*Providencia
*Salmonella
*Shigella
*Yersinia
Plesiomonaceae
*Plesiomonas
Class Enterobacteriales contains organisms that live in the intestinal tracts
of humans or other organisms. Species in Class Enterobacteriales are com-
monly known as enterobacteria, and they fall into one of two subclasses:
Class Enterobacteriaceae and Class Plesiomonaceae.
Enterobacteria include many organisms; some are aerobic, others are anaer-
obic; most are facultative anaerobes. Many enterobacteria are non-pathogenic
commensals, that live in the human intestines, becoming pathogenic under
abnormal circumstances. Other enterobacteria are always pathogenic. The
enterobacteria are rod-shaped. Most are about 1
5 microns in length.
Edwardsiella contains several species that live in a variety of animals,
including snakes, seals, and fish. A rare disease, Edwardsiellosis typically
occurs after ingestion of insufficiently cooked freshwater fish (which harbors
the organism in its GI tract). Most cases occur in tropical climates (e.g.,
Southeast Asia, India, Cuba). A case possibly contracted from ornamental
(aquarium) fish has been reported [34]. The disease usually presents in
humans as a gastroenteritis which may be severe, and occasionally fatal.
Enterobacter contains rod-shaped species that live in the human intestines.
Several enterobacters are opportunistic pathogens, including Enterobacter
aerogenes and Enterobacter cloacae. Disease caused by Enterobacter species
usually involves the urinary tract and the lungs.
Escherichia is another rod-shaped factultatively anaerobic genus with
species that inhabit the human intestine. Most species of Escherichia are
non-pathogenic commensals. Other species cause enteritis or urinary tract
infections. Escherichia coli has pathogenic and non-pathogenic strains, and
is the Escherichia species most commonly responsible for human disease.
One strain of Escherichia coli (strain O157:H7) produces a toxin (shiga-like
toxin) that confers heightened pathogenicity, producing a hemorrhagic enteri-
tis. This dangerous strain of Escherichia coli is transmitted to humans, often
by ingesting contaminated beef, water, or vegetables that have not been
properly sanitized.
Genus Klebsiella contains several species of rod-shaped bacteria with
thick polysaccharide capsules. Species are found throughout the environment.
