Download What is an E. Coli Infection? Escherichia coli commonly abbreviated

E. Coli Infection
What is an E. Coli Infection?
Escherichia coli commonly abbreviated E. coli , was discovered by German
pediatrician and bacteriologist Theodor Escherich in 1885, and classified as part
of the Enterobacteriaceae family of gamma-proteobacteria ,it is commonly found
in the lower intestine of warm-blooded organisms (endotherms). Most E. coli
strains are harmless, but some serotypes can cause serious food poisoning in
humans, and are occasionally responsible for product recalls. The harmless
strains are part of the normal flora of the gut, and can benefit their hosts by
producing vitamin K2, and by preventing the establishment of pathogenic
bacteria within the intestine.
E. coli cells are a major component of feces, and fecal-oral transmission is the
major route through which pathogenic strains of E. coli cause disease. Cells are
able to survive outside the body for a limited amount of time, which makes them
ideal indicator organisms to test environmental samples for fecal contamination.
The bacterium can also be grown easily and inexpensively in a laboratory setting,
and has been intensively investigated for over 60 years. E. coli is the most
widely-studied prokaryotic model organism, and an important species in the
fields of biotechnology and microbiology, where it has served as the host
organism for the majority of work with recombinant DNA
E. coli is facultative anaerobic and non-sporulating. It can live on a wide variety
of substrates. E. coli uses mixed-acid fermentation in anaerobic conditions,
producing lactate, succinate, ethanol, acetate and carbon dioxide. Since many
pathways in mixed-acid fermentation produce hydrogen gas, these pathways
require the levels of hydrogen to be low, as is the case when E. coli lives together
with hydrogen-consuming organisms, such as methanogens or sulphate-reducing
bacteria.
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Optimal growth of E. coli occurs at 37°C but some laboratory strains can
multiply at temperatures of up to 49°C. Growth can be driven by aerobic or
anaerobic respiration, using a large variety of redox pairs, including the oxidation
of pyruvic acid, formic acid, hydrogen and amino acids, and the reduction of
substrates such as oxygen, nitrate, dimethyl sulfoxide and trimethylamine Noxide. Strains that possess flagella can swim and are motile. The flagella have a
peritrichous arrangement.
E. coli and related bacteria possess the ability to transfer DNA via bacterial
conjugation, transduction or transformation, which allows genetic material to
spread horizontally through an existing population. This process led to the spread
of the gene encoding shiga toxin from Shigella to E. coli O157:H7, carried by a
bacteriophage.
Several different strains of harmful E. coli can cause diarrhea disease. A
particularly dangerous type is called enterohemorrhagic E. coli, or EHEC.
EHEC often causes bloody diarrhea and can lead to kidney failure in children or
people with weakened immune systems.
In 1982, scientists identified the first dangerous strain in the United States. The
type of harmful E. coli most commonly found in this country is named O157:H7,
which refers to chemical compounds found on the bacterium's surface.
EHEC produce one or more related, powerful toxins called verotoxin, named for
its cytotoxic effect on vero cell. Vero toxin has many properties that are similar
to shiga toxin produced by some strain of shigella dysenteriae type1.EHEC has
been associated with hemorrhagic colitis, a sever form of diarrhea , and with
Hemolytic uremic syndrome , adisease resulting in acute renal failure,
microangiopathic hemolytic anemia and thrombocytopenia. Other types,
including O26:H11 and O111:H8, also have been found in this country and can
cause human disease.
Cattle are the main sources of E. coli O157:H7, but other domestic and wild
mammals also can harbor these bacteria.
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E. coli outbreak: German origin
The outbreak of E. coli infections in Germany and 11 other countries has
continued to spread, and infected thousands more , including 39 deaths, reported,
the United Nations World Health Organization (WHO) until 17 June 2011.
According to(WHO) any of those infected with the enterohaemorrhagic E. coli
(EHEC) bacteria have developed haemolytic uraemic syndrome (HUS), which
can be fatal . Eleven other European countries – Austria, the Czech Republic,
Denmark, France, Netherlands, Norway, Poland, Spain, Sweden, Switzerland and
the United Kingdom – reported a total of HUS cases,
In the United States, the Centers for Disease Control and Prevention, had earlier
reported many cases of HUS, both linked to the outbreak in outbreak in Europe
through travel.
Early information suggests that the current outbreak might be associated with
contaminated produce (cucumbers, tomatoes and lettuce). At this time, bean
sprouts have been identified as the possible cause of this outbreak based on
current evidence, according to say German health authorities.
Figure 1.The cause of the E coli outbreak has been officially linked in
Germany to the consumption of bean sprouts. Photograph: 10 June 2011 .
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Symptoms of E. Coli Infection
Symptoms of E. Coli infection usually begin 2 to 5 days after exposure. The
symptoms may last for 8 days. Some common symptoms of infection with E. coli
O157:H7 are:

Nausea

Severe abdominal cramps

Watery or very bloody diarrhea

Fatigue

Low grade fever
Other types of E. Coli Can Cause Diarrhea Disease.
Enterotoxigenic E. coli (ETEC), which produce a toxin similar to Cholera toxin,
can cause diarrhea. These strains typically cause so-called travelers diarrhea
because they commonly contaminate food and water in developing countries.
Enteropathogenic E. coli (EPEC) are associated with persistent diarrhea (lasting 2
weeks or more) and are more common in developing countries where they can be
transmitted by contaminated water or contact with infected animals.
Complications of E. Coli infection
One of the most serious complications of an E. Coli infection is Hemolytic
uremic syndrome. Hemolytic uremic syndrome is characterized by destruction of
red blood cells, damage to the lining of blood vessel walls, and, in severe cases,
kidney failure.
Transmittion of E. Coli infection
E. coli bacteria and its toxins have been found are transmitted to humans via:

Undercooked or raw hamburgers

Salami

Alfalfa sprouts
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
Lettuce

Un pasteurized milk, apple juice, and apple cider

Contaminated well water

Contaminated swimming pools

Contaminated oceans and lakes
Prevention of E. Coli Infection

Eat only thoroughly cooked beef and beef products.

Cook ground beef patties to an internal temperature of 160 degrees
Fahrenheit.

Avoid unpasteurized juices.

Drink only pasteurized milk.
Wash fresh fruits and vegetables thoroughly before eating raw or cooked.
Treatment of E. Coli infection
The current epidemic strain is very multi-drug resistant so is not affected by at
least 12 antibiotics or antibiotic combinations. Regardless, antibiotics are not
typically used to treat infection with Shiga toxin-producing E. coli to prevent
more toxin from being released from the dead bacteria and doing more damage.
Furthermore, antibiotics can themselves be toxic to the kidneys, particularly
aminoglycosides. In the case of E. coli O157:H7 and perhaps O104:H4, the
virulence gene that codes for the Shiga toxin is part of a bacterial viral genome
recombined into the bacterial pathogen’s genome in a way that keeps toxin
expression and viral infection turned off. Exposure to ciprofloxacine, a
fluoroquinolone antibiotic, would do double harm, turning on expression of the
Shiga toxin gene and awakening the latent virus that starts to reproduce and lyse
the bacteria now full of toxin.
German clinicians started to use eculizumab aka Soliris to help minimize
intravenous blood cell lysis in infected patients. This is an off label experimental
use for this monoclonal antibody therapy manufactured by Alexion
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Pharmaceuticals to treat patients with paroxysmal nocturnal hemoglobinuria
(PNH), a genetic disorder that affects the regulation of complement, a component
of the innate immune system. Eculizumab is comprised of recombinant
monoclonal antibody that binds to complement C5, one of several blood serum
complement protein types, to prevent its activation and that of a cascade of
reactions that leads to formation of Membrane Attack Complex (C5b-9) that
pokes a hole in the cell envelope of Gram negative bacteria such as E. coli to kill
them by cell lysis.
Laboratory diagnosis of E. Coli
In stool samples, microscopy will show Gram-negative rods, with no particular
cell arrangement. Then, either MacConkey agar or EMB agar (or both) are
inoculated with the stool. On MacConkey agar, deep red colonies are produced,
as the organism is lactose-positive, and fermentation of this sugar will cause the
medium's pH to drop, leading to darkening of the medium. Growth on Levine
EMB agar produces black colonies with a greenish-black metallic sheen. This is
diagnostic of E. coli.
Figure 2. An employee holds petri dishes with bacterial strains of EHEC bacteria
(bacterium Escherichia coli.) in the microbiological laboratory of the University
Clinic Eppendorf- UKE in the northern German town of Hamburg, June 8, 2011
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The organism is also lysine positive, and grows on TSI slant with a (A/A/g+/H2S) profile. Also, IMViC is {+ + – –} for E. coli; as it is indole-positive (red ring)
and methyl red-positive (bright red), but VP-negative (no change-colourless) and
citrate-negative (no change-green colour). Tests for toxin production can use
mammalian cells in tissue culture, which are rapidly killed by shiga toxin.
Although sensitive and very specific, this method is slow and expensive.
Typically, diagnosis has been done by culturing on sorbitol-MacConkey medium
and then using typing antiserum. However, current latex assays and some typing
antisera have shown cross reactions with non-E. coli O157 colonies.
Furthermore, not all E. coli O157 strains associated with HUS are nonsorbitol
fermentors.
The Council of State and Territorial Epidemiologists recommend that clinical
laboratories screen at least all bloody stools for this pathogen. The American
Gastroenterological Association Foundation (AGAF) recommended in July 1994
that all stool specimens should be routinely tested for E. coli O157:H7.[citation needed]
Clinicians are advised to check with their state health department or the Centers
for Disease Control and Prevention to determine which specimens should be
tested and whether the results are reportable.
Other methods for detecting E. coli O157 in stool include ELISA tests, colony
immunoblots, direct immunofluorescence microscopy of filters, as well as
immunocapture techniques using magnetic beads. These assays are designed as
screening tool to allow rapid testing for the presence of E. coli O157 without
prior culturing of the stool specimen.
Fluorescence microscopy and laser scanning confocal microscopy (LSCM).
Sections of seedlings were further examined by fluorescence microscopy on days
3, 6, and 9 post planting. Samples were stained with propidium iodide (10 µg ml –
1
; Molecular Probes, Eugene, Oreg.) for 30 min, washed twice in phosphate-
buffered saline (Sigma), and then mounted on glass microscope slides and
examined with an Olympus BH-2 epifluorescence microscope equipped with a
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100x oil objective. Images were captured with a charge-coupled device camera
(Photometrics, Tucson, Ariz.) and formatted using Adobe Photoshop. Cells of E.
coli O157:H7/pGFP were visualized on the cotyledons and hypocotyl of the
lettuce seedlings, regardless of the level of soil contamination or day of sampling
(Fig.3). The surfaces of the seedlings likely became contaminated as the seedlings
grew and broke through the soil surface.
Figure 3. Photomicrograph showing colonization of the surface of a 3-dayold lettuce seedling grown in soil containing 106 CFU of E. coli
O157:H7/pGFP g–1. Cells appear as aggregates and attach preferentially to
junction zones of lettuce cells. The arrow indicates foci of E. coli O157:H7
cells.
By
Supervisor
Abbas Sahib Al-Naffakh.
Dr. Mohammed Mahdi Al-Jawaheri.
MSC. Med . Tech.
D. C. Pathology.
Laboratory Office.
Manager of Laboratory Office.
Department of Technical Affairs.
Al-Najaf Health Directorate.
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