- Normal flora of the intestinal
tract in humans and animals.
- Usually the patient's own fecal
flora; some transmission is patient-to-patient.
- E. coli causes around 80
percent of all uncomplicated urinary tract infections (UTIs)
and more than 50 percent of nosocomial (def)
UTIs. UTIs account for more than 7, 000,000 physician office visits per year
in the U.S. Between 35 and 40 percent of all nosocomial infections, about
900,000 per year in the U.S., are UTIs and are usually associated with urinary
- E. coli causes wound
infections, usually a result of fecal contamination of external wounds
or a result of wounds that cause trauma to the intestinal tract, such as surgical
wounds, gunshot wounds, knife wounds, etc.
- E. coli is by far the most
common gram-negative bacterium causing sepsis. Septicemia
is a result of bacteria getting into the blood. They are usually introduced
into the blood from some other infection site, such as an infected kidney,
wound, or lung. There are approximately 500,000 cases of septicemia per year
in the U.S. and the mortality rate is between 20 and 50 percent. Over 175,000
people a year in the U.S. die from septic shock. Approximately 45 percent
of the cases of septicemia are due to gram-negative bacteria. Klebsiella,
Proteus, Enterobacter, Serratia, and E. coli, are all common gram-negative
bacteria causing septicemia.
- E. coli, along with group
B streptococci, are the leading cause of neonatal meningitis
- While E. coli is one of
the dominant normal flora in the intestinal tract of humans and animals, some
strains can cause gastroenteritis, an infection of the intestinal
- Enterotoxigenc E. coli
(ETEC) produce enterotoxins that cause the loss of sodium ions and water
from the small intestines resulting in a watery diarrhea. Over half of
all travelers' diarrhea is due to ETEC; almost 80,000 cases a year in
- Enteropathogenic E. coli
(EPEC) cause an endemic diarrhea in areas of the developing world, especially
in infants younger than 6 months. The bacterium disrupts the normal microvilli
on the epithelial cells of the small intestines resulting in maladsorbtion
- Enteroaggregative E. coli
(EAEC) is a cause of persistant diarrhea in developing countries. It probably
causes diarrhea by adhering to mucosal epithelial cells of the small intestines
and interfering with their function.
- Enteroinvasive E. coli
(EIEC) invade and kill epithelial cells of the large intestines causing
a dysentery-type syndrome similar to Shigella common in underdeveloped
- Enterohemorrhagic E. coli
(EHEC), such as E. coli 0157:H7, produce a shiga-like toxin that
kills epithelial cells of the large intestines causing hemorrhagic colitis,
a bloody diarrhea. In rare cases, the shiga-toxin enters the blood and
is carried to the kidneys where, usually in children, it damages vascular
cells and causes hemolytic uremic syndrome. E. coli 0157:H7 is
thought to cause more than 20,000 infections and up to 250 deaths per
year in the U.S.
- Diffuse aggreegative E.
coli (DAEC) causes watery diarrhea in infants 1-5 years of
age. They stimulate elongation of the microvilli on the epithelial cells
lining the small intestines.
- In the outer membrane of the gram-negative
cell wall, the lipopolysaccharide functions as an endotoxin . Endotoxin, especially
when in the blood, can lead to inflammation, high fever, hypotension, capillary
damage, intravascular coagulation, tissue degradation, and irreversible shock.
Death is a result of what is called the shock cascade (see
- Various types of pili
enable the bacterium to initially adhere to epithelial cells of the mucous
- A variety of cell wall adhesins
enable the bacterium to make a more intimate contact with the mucous membranes.
- Some strains (ETEC) secrete enterotoxins
that cause the loss of sodium ions and water from the small intestines resulting
in a watery diarrhea.
- Some strains (EHEC) secrete a
shiga-like toxin that kills epithelial cells of the large intestines causing
hemorrhagic colitis (def),
a bloody diarrhea.
- Uncomplicated symptomatic acute
cystitis and/or urethritis are usually treated for three days with trimethoprim-sulfamethoxazole
(TMP-SMX), norfloxacin, or ciprofloxacin* (see antibiotic
table). In vitro antibiotic susceptibility tests usually guide treatment
of more complicated infections.
*Drugs may change with time.
For a more detailed article on Escherichia
coli infections, see
infections, by Chi Hiong U Go, MD, Assistant Professor, Department of Internal
Medicine, Texas Tech University Health Science Center at Odessa and
Burke A Cunha, MD, Professor of Medicine,
State University of New York at Stony Brook School of Medicine; Chief, Infectious
Disease Division, Vice-Chair, Department of Internal Medicine, Winthrop-University
Kaiser's Microbiology Home Page
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Updated: January 4, 2005
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