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Escherichia coli

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E. coli redirects here. See also Entamoeba coli.

Escherichia coli
Scientific classification
Superdomain:
Phylogenetica
Phylum:
Proteobacteria
Class:
Gamma Proteobacteria
Order:
Enterobacteriales
Family:
Enterobacteriaceae
Genus:
Escherichia
Species:
E. coli
Binomial name
Escherichia coli
T. Escherich, 1885
Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped.

Escherichia coli (IPA: [ˌɛ.ʃəˈɹɪ.kjə ˈkʰoʊ.laɪ]), usually abbreviated to E. coli, (coli is Latin for "of the colon") was discovered in 1885 by Theodor Escherich, a German pediatrician and bacteriologist.[1] It is one of the main species of bacteria living in the lower intestines of mammals, known as gut flora. The number of individual E. coli bacteria in the feces that a human excretes in one day averages between 100 billion and 10 trillion.[citation needed] However, the bacteria are not confined to this environment, and specimens have also been located, for example, on the edge of hot springs. The E. coli strain O157:H7 is one of hundreds of strains of the bacterium E. coli that causes illness in humans, according to US Department of Health and Human Services Centers for Disease Control and Prevention.

All the different kinds of fecal coli bacteria, and all the very similar bacteria that live in the ground (in soil or decaying plants, of which the most common is Enterobacter aerogenes), are grouped together under the name coliform bacteria. Technically, the "coliform group" is defined to be all the aerobic and facultative anaerobic, non-spore-forming, Gram-negative, rod-shaped bacteria that ferment lactose with the production of gas within 48 hours at 35 °C (95 °F). In the body, this gas is released as flatulence. E. coli cells are elongated, 1–2 µm in length and 0.1–0.5 µm in diameter.

The presence of coliform bacteria in surface water is a common indicator of fecal contamination. E. coli is commonly used as a model organism for bacteria in general. One of the root words of the family's scientific name, "enteric", refers to the intestine, and is often used synonymously with "fecal".

As Gram-negative organisms, E. coli are unable to sporulate. Thus, treatments which kill all active bacteria, such as Pasteurization or simple boiling, are effective for their eradication, without requiring the more rigorous sterilization which also deactivates spores.

As a result of their adaptation to mammalian intestines, E. coli grow best in vivo or at the higher temperatures characteristic of such an environment, rather than the cooler temperatures found in soil and other environments.

Role in water purification and sewage treatment

In the field of water purification and sewage treatment, E. coli was chosen very early in the development of the technology as an "indicator" of the pollution level of water, meaning the amount of human fecal matter in it, measured using the Coliform Index. E. coli is used for detection because there are a lot more coliforms in human feces than there are pathogens (Salmonella typhi is an example of such a pathogen, causing typhoid fever), and E. coli is usually harmless, so it can't "get loose" in the lab and hurt anyone. However sometimes it can be misleading to use E. coli alone as an indicator of human fecal contamination because there are other environments in which E. coli grows well, such as paper mills.

Role in disease

E. coli can generally cause several intestinal and extra-intestinal infections such as urinary tract infections, meningitis, peritonitis, mastitis, septicemia and gram-negative pneumonia. The enteric E. coli are divided on the basis of virulence properties into enterotoxigenic (ETEC, causative agent of diarrhea in humans, pigs, sheep, goats, cattle, dogs, and horses), enteropathogenic (EPEC, causative agent of diarrhea in humans, rabbits, dogs, cats and horses); enteroinvasive (EIEC, found only in humans), verotoxigenic (VTEC, found in pigs, cattle, dogs, and cats); enterohaemorrhagic (EHEC, found in humans, cattle, and goats), attacking porcine strains that colonize the gut in a manner similar to human EPEC strains) and enteroaggregative E. coli (EAggEC, found only in humans).

The often harmless E. coli can cause illness either by infection of a bodily cavity where it is not normally found, or by synthesis of a toxin which attacks the body. In the first case, the disease can usually be resolved by use of antibiotics that stop the infection, but in the latter case the effects of the toxin persist after the bacteria have been killed. Examples of situations in which E. coli can cause illness are

1. When the bacteria travel from the stomach to the intestinal tract, and into the urinary tract, they can cause an infection sometimes referred to as "honeymoon cystitis" because sexual intercourse can lead to introduction of bacteria into the bladder: this is particularly true if anal intercourse is followed by vaginal intercourse, a practice deprecated by such authorities as Nina Hartley but occasionally seen in pornographic movies.

Although it is more common in females due to the shorter urinary tract, urinary tract infection is seen in both males and females. It is found in roughly equal proportions in elderly men and women. Since bacteria invariably enter the urinary tract through the urethra, poor toilet habits can predispose to infection(doctors often advise women to "wipe front to back, not back to front."; but other factors are also important (pregnancy in women, prostate enlargement in men) and in many cases the initiating event is unclear.

2.In the May 2005 Journel of Infectious Diseases, Lisa Jackson et al of Group Seattle reported based on a study of Group Health's 46,000 members,that E. coli bacteremia may affect as many as 53,000 non-institutionalized people, aged 65 and older, each year, with a death rate of about 10%. Risk factors for Bacteremia included incontinence, congestive heart failure, and coronary artery disease. [6]

3. When the bacteria escape the intestinal tract through a perforation (a hole or tear, for example from an ulcer, a ruptured appendix, or a surgical error) and enter the abdomen, they usually cause an infection called "peritonitis" that can be fatal without prompt treatment. However, E. coli are extremely sensitive to such antibiotics as streptomycin or gentamycin, so treatment with antibiotics is usually effective. This could rapidly change as noted below, e coli rapidly aquires drug resistance. [7]


4. Certain strains of E. coli, such as Escherichia coli O157:H7, are toxigenic (some produce a toxin very similar to that seen in dysentery) and can cause food poisoning usually associated with eating cheese and contaminated meat (contaminated during or shortly after slaughter or during storage or display). The usual countermeasure is cooking suspect meat "well done"; the alternative of careful inspection of slaughtering and butchering methods (to make sure that the animal's colon is removed and not punctured) has apparently not been systematically tried. This particular strain is believed to be associated with the 2006 United States E. coli outbreak linked to fresh spinach. Severity of the illness varies considerably; it can be fatal, particularly to young children, the elderly or the immunocompromised, but is more often mild. E. coli can harbor both heat-stable and heat-labile enterotoxins. The latter, termed LT, is highly similar in structure and function to Cholera toxin. It contains one 'A' subunit and five 'B' subunits arranged into one holotoxin. The B subunits assist in adherence and entry of the toxin into host intestinal cells, where the A subunit is cleaved and prevents cells from absorbing water, causing diarrhea. LT is secreted by the Type 2 secretion pathway[2]

5.It has also been shown that STECs, specifically O157:H7 can be found in filth flies on cattle farms, in house flies, can grow on wounded fruit and transmitted to and by fruit flies. [8][9][10]

  1. Since toxigenic coli can be resident in animals which are resistant to the toxin, they may be spread through direct contact on farms, at petting zoos, etc. They may also be spread via airborne particle in such environments.[3] The government asked in 1978 what would the effect be of overfeeding animals antibiotics. The American Academy of Science produced the result that antibiotic resistant E. coli would develop and would be untreatable. The first deaths from Ecoli:0:157:H7 occurred in Canada in 1982. This information was passed on to a public inquiry into the deaths of 24 people in Scotland in 1995. The inquiry refused to allow this public knowledge into the public domain. This information is glaring in its absence in all discussion and news of E. coli 157:H7 outbreaks.
  2. E coli is a frequent member of multispecies biofilms. Some strains are piliated and capable of accepting and transferring plasmids (rings of DNA) from and to other bacteria of the same and different species. E. coli often carry multidrug resistant plasmids and under stress readily transfer those plasmids to other species. Thus E. coli and the other enteroccia are important reservoirs of transferable antibiotic resistance. [4][5]

E. coli Bacteria Make Alzheimer’s-linked Fibers [6][7]

Appropriate treatment depends on the disease and should be guided by laboratory analysis of the antibiotic sensitivities of the infecting strain of E. coli. As Gram-negative organisms, coli are resistant to many antibiotics which are effective against Gram-positive organisms. Antibiotics which may be used to treat E. coli infection include (but are not limited to) amoxicillin, trimethoprim-sulfamethoxazole, ciprofloxacin, nitrofurantoin. Not all antibiotics are suitable for every disease caused by E. coli, and the advice of a physician should be sought.

Antibiotic resistance is a growing problem. Some of this is due to overuse of antibiotics in humans, but some of it is probably due to the use of antibiotics as growth promoters in food animals.[8]

Quinine has been shown to inhibit the ability of E. coli to invade human epithieal cells in a dose dependent manner.[9] In addition, low doses of quinine and some local anaesthetics have been found to increase antibiotic penetration of the E. coli cell membrane, and increase antibiotic susceptibility by a factor of from 2 to 10. [10]

Based on the effectiveness of quinine in preventing cell invasion both by e-coli and malaria, research to evaluate arsunate and propranolol against e-coli might yeild some useful results as Northwestern University researchers recently been found that the drug propranolol inhibits the ability of the malaria parasite to invade red blood cells, and reduces the dose of adjunt antimalarial drugs necessary to eradicate the parasite by a factor of 10. [11]

The anti-inflammatory drug Diclofenac exhibits significant antibacterial activity against multidrug resistant strains of E. coli both in vitro and in vivo. Isolates resistant to ampicillin, tobramycin, augmentin, nalidixic acid, cefuroxime, nitrofurantoin, kanamycin, pipemidic acid, chloramphenicol, cefotaxime, cefamendol, ofloxacin, ceftizoxime, norfloxacin and amikacin were tested. All isolates were sensitive to Diclofenac. The MIC90 was 25 microG/mL. [11]

Vaccine

The NIH reported e-coli vaccine was proved safe and effective in preliminary trials in 1998. [12]

In 1999 the WHO published a report where they reviewed the vaccines developed up until that time.[13] They note that STEC (Shiga toxin producing e-coli) and EHEC (enterohaemorrhagic e-coli) infections pose a significant burden in terms of human disease, and pose one of the leading causes of renal failure. They report development of 6 vaccines some of which sucessfully protected adult humans and animals in labratory modles, but note that while the vaccines protect suceptible labratory animals such as suckling rabbits from developing the disease, they do NOT PREVENT COLONIZATION of with the bacteria. The report also mentions the low inoculum (low number of bacteria) required to transmit the disease. STECs have high competetive fitness, only 10 to 100 organisms are required to transmit the disease. [14] As noted above, It has also been shown that STECs, specifically O157:H7 is found in filth flies and can be carried in fruit flies. [15]


In January 2007 the Canadian bio-pharmaceutical company Bioniche announced it has developed a vaccine which reduces the number of bacteria shed in manure by a factor of 1000, to about 1000 bacteria per gram of manure. [16][17]

In March of 2006, a vaccine eliciting an immune response against the E. coli O157:H7 O-specific polysaccharide conjugated to recombinant exotoxin A of Pseudomonas aeruginosa (O157-rEPA) was reported to be safe and immunogenic in children two to five years old. It has already been proven safe and immunogenic in adults.[18]

And still, to date, 9 years later, no vaccine is yet available to the pulbic.

It seems that the few cases of acute food borne disease each year due to O157:H7 are not considered sufficently costly to justify wide deployment of the vaccine in humans. Weather this vaccine would also confer resistance to Ueropathic and Bacterimic forms of e coli remains to be seen, but if it does it can potentially reduce the disease load on the population by 100,000s of occurances. Since piliated e-coli is an attachment specialist that premotes the aggregation of other species and it's amyloid curli and polysacride attachment stradgey is shared by many other pathogens, [19] it is also possible that the polysacride based e-coli vaccine could reduce host vulnerability to all bio-film infections that depend on e coli or another bacteria producing a polysacride simular enough to elicit a cross reactive immune response for a foothold.

It would be especially interesting if it elicits an immune response against Pseduomonas Aeruginosa as well, as it might also reduce the symptoms of cystic fibrosis and sinusitis. Mixed polysacride containing biofilms have been demonstrated in 3/4 of the cases of chronic sinusitis.Chronic sinusitis affects millions of people. Bhattacharyya found the cost of Chronic Sinusitis to be $1539.00 per patient in his 2003 study including medical costs and time lost from the job. [20] And the Universtiy of Michigan Sinusitis website states that the direct medical cost of Sinusitis is 2.4 Billion not counting lost productivity.[21] Whereas the few cases of food borne disease each year due to O157:H7 might not justify wide deployment of the vaccine, a demonstrating the prospect of substancial cross-reactivity resulting in a substancial reduction cost due to uniary tract infections, bacterimia and sinusitis might change the equation to make the vaccine economicly viable to deploy in humans rather than cattle.

Strains

Model of successive binary fission in E. coli

A "strain" of E. coli is a group with some particular characteristics that make it distinguishable from other E. coli strains. These differences are often detectable only on the molecular level; however, they may result in changes to the physiology or lifecycle of the bacterium, for example leading to pathogenicity. Different strains of E. coli live in different kinds of animals, so it is possible to tell whether fecal material in water came from humans or from birds, for example. New strains of E. coli arise all the time from the natural biological process of mutation, and some of those strains have characteristics that can be harmful to a host animal. Although in most healthy adult humans such a strain would probably cause no more than a bout of diarrhea, and might produce no symptoms at all, in young children, people who are or have recently been sick, or in people taking certain medications, an unfamiliar strain can cause serious illness and even death. A particularly virulent example of such a strain of E. coli is E. coli O157:H7.

In addition, E. coli and related bacteria possess the ability to transfer DNA via bacterial conjugation, which allows a new mutation to spread through an existing population. It is believed that this process led to the spread of toxin synthesis from Shigella to E. coli O157:H7.

Extended-Spectrum Beta-Lactamase (ESBL)–producing E. coli are antibiotic-resistant strains of E. coli. ESBL-producing strains are bacteria that produce an enzyme called extended-spectrum beta lactamase, which makes them more resistant to antibiotics and makes the infections harder to treat. In many instances, only two oral antibiotics and a very limited group of intravenous antibiotics remain effective.

Role in microbiology

Because of its ubiquity, E. coli is frequently studied in microbiology and is the current "workhorse" in molecular biology. Its structure is clear, and it makes for an excellent target for novice, intermediate, and advanced students of the life sciences. The strains used in the laboratory have adapted themselves effectively to that environment, and are no longer as well adapted to life in the mammalian intestines as the wild type; a major adaptation is the loss of the large quantities of external biofilm mucopolysaccharide produced by the wild type in order to protect itself from antibodies and other chemical attacks, but which require a large expenditure of the organism's energy and material resources. This can be seen when culturing the organisms on agar plates; while the laboratory strains produce well defined individual colonies, with the wild type strains the colonies are embedded within this large mass of mucopolysaccharide, making it difficult to isolate individual colonies.

Bacterial conjugation was first discovered in E. coli, and E. coli remains the primary model to study conjugation.

Because of this long history of laboratory culture and manipulation, E. coli plays an important role in modern biological engineering. Researchers can alter the bacteria to serve as "factories" to synthesize DNA and/or proteins, which can then be produced in large quantities using the industrial fermentation processes. One of the first useful applications of recombinant DNA technology was the manipulation of E. coli to produce human insulin for patients with diabetes.[citation needed]

See also

Wikispecies has information related to Escherichia coli.
Wikimedia Commons has media related to Escherichia coli.

References

  1. ^ Feng P, Weagant S, and Grant, M. Enumeration of Escherichia coli and the Coliform Bacteria, in BACTERIOLOGICAL ANALYTICAL MANUAL (8th ed. 2002)
  2. ^ Tauschek M, Gorrell R, Robins-Browne RM,. "Identification of a protein secretory pathway for the secretion of heat-labile enterotoxin by an enterotoxigenic strain of Escherichia coli". PNAS. 99: 7066–7071.{{cite journal}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link)
  3. ^ Christie, Tim (2002-09-24). "Tests suggest E. coli spread through air". The Register-Guard. Retrieved 2007-01-05. {{cite news}}: Check date values in: |accessdate= and |date= (help)
  4. ^ [1]
  5. ^ [2]
  6. ^ Chapman MR, Robinson LS, Pinkner JS, Roth R, Heuser J, Hammar M, Normark S, Hultgren SJ. Escherichia coli curli operons direct amyloid fiber formation. Science, 295 (5556), 851-855, Feb. 1, 2002.
  7. ^ Research in the Chapman Lab, University of Michigan
  8. ^ Johnson JR, Kuskowski MA,Menard M; et al. "Similarity between human and chicken Escherichia coli isolates in relation to ciprofloxacin resistance status". J Infect Dis. 194: 71–8. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
  9. ^ [3]
  10. ^ [4]
  11. ^ [5]
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