Escherichia coli (E.Coli)

One of the most common coliform bacteria types.

Escherichia coli, also known as E. coli.

E. coli is the type species of the genus (Escherichia) and in turn Escherichia is the type genus of the family Enterobacteriaceae.

A Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine.

Escherichia coli is one of the most frequent causes of many common bacterial infections, including: cholecystitis, cholangitis, urinary tract infection (UTI), traveler’s diarrhea, neonatal meningitis, pneumonia and sepsis.

E. coli is one of the main causes of urinary tract infections.

As E. coli is part of the normal microbiota in the gut it can be introduced in many ways.

Enterotoxigenic E. coli (ETEC) is the most common cause of traveler’s diarrhea.

The incubation period is usually 3–4 days after the exposure.

The incubation period may be as short as 1 day or as long as 10 days before traveler’s diarrhea.

Traveler’s diarrhea symptoms often begin slowly with mild belly pain or non-bloody diarrhea that worsens over several days.

Management involves assessment of dehydration and replacement of fluid and electrolytes.

Antibiotics shortens the course of illness and duration of excretion of enterotoxigenic E. coli (ETEC) in adults in endemic areas and in traveller’s diarrhea,.

The rate of antibiotic resistance is increasing so they are generally not recommended.

The antibiotics of choice are fluoroquinolones or azithromycin, with an emerging role for rifaximin.

Oral rifaximin, a semisynthetic rifamycin derivative.

Oral rifaximin is an effective and well-tolerated antibacterial for the management of adults with non-invasive traveller’s diarrhea.

Rifaximin is effective in patients with E. coli-predominant traveller’s diarrhea, but ineffective in patients infected with inflammatory or invasive enteropathogens.

Most E. coli strains are harmless.

Five subspecies of E. coli are distinguished.

Genes in E. coli are usually named by 4-letter acronyms that derive from their function and italicized.

E. coli belongs to a group of bacteria informally known as coliforms that are found in the gastrointestinal tract of warm-blooded animals.

Nonpathogenic E. coli strain Nissle 1917, (Mutaflor) and E. coli O83:K24:H31 (Colinfant)are used as probiotic agents.

The complete DNA sequence of an E. coli genome is a circular DNA molecule 4.6 million base pairs in length, containing 4288 annotated protein-coding genes, seven ribosomal RNA operons, and 86 transfer RNA genes.

Sequences shows a lot of diversity, with only about 20% of each genome represents sequences present in every one of the isolates, and around 80% of each genome can vary among isolates.

Each individual genome contains between 4,000 and 5,500 genes, but the total number of different genes among all of the sequenced E. coli strains (exceeds 16,000).

More than three hundred complete genomic sequences of Escherichia and Shigella species are known.

It is expelled into the environment within feces.

The bacterium grows in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline thereafter.

The outer membrane surrounding the cell wall provides a barrier to certain antibiotics.

E. coli is not damaged by penicillin.

Strains may possess flagella .

Optimum growth of E. coli occurs at 37 °C (98.6 °F).

Their survival is increased in environments where water predominates.

E. coli can transfer DNA via bacterial conjugation or transduction, which allows genetic material to spread horizontally through an existing population.

E. coli exhibit a very high degree of both genetic and phenotypic diversity, and remains one of the most diverse bacterial species: only 20% of the genes in a typical E. coli genome is shared among all strains.

A common subdivision system of E. coli, is by serotype, which is based on major surface antigens (O antigen: part of lipopolysaccharide layer; H: flagellin; K antigen: capsule).

The process of transduction using the bacterial virus called a bacteriophage, is where the spread of the gene encoding for the Shiga toxin from the Shigella bacteria to E. coli helped produce E. coli O157:H7, the Shiga toxin-producing strain of E. coli.

Some strains of E. coli, O157:H7, can produce Shiga toxin, which causes inflammation in the cells of the gut, which results in bloody diarrhea that is a symptom of a Shiga toxin-producing E. coli (STEC) infection.

Shiga toxin causes red blood cell lysis, kidney impairment and in some rare cases the hemolytic-uremic syndrome (HUS), which may lead to kidney failure and even death.

Infection can lead to hemolytic uremic syndrome (HUS), characterized by hemolytic anemia, thrombocytopenia, and renal injury.

If HUS develops from E. Coli develops, it occurs an average 7 days after the first symptoms, when the diarrhea is improving.

It is classified as a facultative anaerobe.

Facultative anaerobes refers to bacteria that can grow in either the presence or absence of oxygen.

E. Coli remain benign commensals, unless they acquire genetic alterations encoding for virulence factors.

Most E. coli strains do not cause disease, naturally living in the gut.

It uses oxygen when it is present and available, but can continue to grow in the absence of oxygen using fermentation or anaerobic respiration.

In the laboratory E. coli typically do not have the ability to grow aerobically with citrate as a carbon source, which is used as a diagnostic criterion with which to differentiate E. coli from other, closely, related bacteria such as Salmonella.

E. coli and other facultative anaerobes constitute about 0.1% of gut microbiome.

Some serotypes of E. coli strains can cause food poisoning.

Certain strains of E. coli are a major cause of foodborne illness.

The harmless strains of E. coli strains are part of the normal microbiota of the gut.

E. coli strains produce vitamin K2, and prevents colonization of the intestine with pathogenic bacteria.

It makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.

The cells are typically rod-shaped, and are about 2.0 μm long and 0.25–1.0 μm in diameter, with a cell volume of 0.6–0.7 μm3.

A nonsporulating bacterium.

Escherichia organisms are gram-negative bacilli that exist singly or in pairs.

A facultatively anaerobic organism with a metabolism that is fermentative and respiratory.

Either nonmotile or motile by flagella.

Major facultative inhabitant of the large intestine.

Detection of E. coli is definite evidence of fecal pollution.

The fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease.

It is Gram-negative on staining as its cell wall is composed of a thin peptidoglycan layer and an outer membrane.

E. coli stains Gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane.

Facultatively anaerobic gram-negative rods that live in the intestinal tracts of animals.

Can grow in the presence or the absence of oxygen.

Under anaerobic conditions, E. coli grow by fermentation, producing mixed acids and gases as end products.

Can also grow by anaerobic respiration, utilizing NO3, NO2, or fumarate.

Known for its ability to cause intestinal diseases.

Most types of E. coli bacteria live in our guts, in the intestines of other animals, and in land and water.

Some help in the digestion process.

Some types of E. coli can cause bloody diarrhea, nausea, vomiting, cramps, and food poisoning.

Such bad E. Coli bacteria are usually found in human or animal feces.

About 85% of E. coli pathogens are transmitted to humans through food, often ground beef that becomes contaminated during processing,

The ground beef that ends up in supermarkets and eventually on dinner tables usually combines meat from many different animals, increasing the risk that it’s contaminated.

Raw vegetables that have come into contact with runoff from cattle farms are another cause of E. coli infections: Spinach, lettuce, and alfalfa sprouts are examples.

Cattle can transmit E. coli bacteria through their milk, and infect soft cheeses.

That is why drinking only pasteurized milk is necessary.

Juices made from fruits and vegetables must be be pasteurized.

Flour comes from grains that grows in field where cattle and other animals may have deposited waste.

Water is a potential reservoir of E. coli, with human or animal fecal contamination.

E. coli can be communicated by either human-to-human or animal-to-human contact.

E. coli can spread from an infected person’s hands to other people or even to objects.

Six classes of E. coli can result in diarrheal diseases, but three specific pathogenic strains—enterotoxigenic, enteropathogenic, and enteroinvasive—cause problems when present in the water supply.

E. coli-induced diarrhea can have a fatality rate as high as 40 percent in newborn children.

E. Coli bacteria have P fimbriae that facilitate uro epithelial attachment, even with adequate urine flow.

Enterotoxigenic E. coli are an important cause of diarrhea in infants, and in travelers to areas with poor sanitation, and are acquired by ingestion of contaminated food and water.

As many as 840 million cases worldwide of traveler’s diarrhea reported in developing countries each year.

Bacteria responsible for traveler’s diarrhea are typically transmitted through contaminated food or drinking water.

The transmitted bacteria adhere to the intestinal lining, and secretes either of two types of enterotoxins, leading to watery diarrhea.

The rate and severity of traveler’s diarrheal infections are higher among children under the age of five, including as many as 380,000 deaths annually.

Adults in endemic areas with Enterotoxigenic E. coli develop immunity.

The primary symptom of Enterotoxigenic E. coli infection is diarrhea without fever.

Enteroinvasive E. coli penetrate and multiply within epithelial cells of the colon and cause widespread cell destruction.

Enteroinvasive E. coli infections are endemic in developing countries.

Enteropathogenic E. coli are an important cause of traveler’s diarrhea.

Enteropathogenic E. coli produce watery diarrhea.

At present, there about 190 serogroups described.

Virulent strains typically cause a bout of diarrhea that is often self-limiting in healthy adults but is frequently lethal to children in the developing world.

The virulent strain O157:H7, can cause serious illness or death in the elderly, the very young, or the immunocompromised.

Escherica coli 0157:H7 is one if the more virulent of the many strains of E.coli.

Virulent strains can cause gastroenteritis, urinary tract infections, neonatal meningitis, hemorrhagic colitis, Crohn’s disease, bowel necrosis, and perforation, hemolytic-uremic syndrome, peritonitis, mastitis, sepsis, and Gram-negative pneumonia.

Very young children are more susceptible to develop severe illness, such as hemolytic uremic syndrome.

Diarrhea associated with hemolytic-uremic syndrome and neurologic complications is generally related to E. Coli that produce Shiga toxin (Kaper JB et al).

Diarrhea associated strains are ref2242ed to as enterohemorrhagic E.coli and they contain the enterocyte effacement pathogenicity island, which facilitates large intestine colonization.

E. coli normally colonizes an infant’s gastrointestinal tract within 40 hours of birth.

Colonization of the GI tract occurs with food or water or from the individuals caring for the neonate.

E. coli adheres to the mucus of the large intestine., and is the primary facultative anaerobe of the human gastrointestinal tract.

Enterovirulent strains are classified into overlappingpathotypes, including Shiga toxin producing, enterohemorrhagic, and enteroaggregative varieties.

Enteroaggregating E. coli implicated as the etiology of travelers diarrhea, childhood diarrhea, HIV infected patients, and probably foodborne outbreaks.

When consumed in water, milk, or food or is transmitted through the bite of a fly or other insect, it can cause gastrointestinal illness.

Mutations can lead to strains that cause diarrhea by giving off toxins, invading the intestinal lining, or sticking to the intestinal wall.

A common uropathogen.

Possesses unique surface adhesins on finbriae and other adhesive organelles.

Adhesives systems promote bacterial adherence to epithelial cell membranes and can colonize the vagina, perineum, and periurethral region with this colonic bacteria.

Methods for prevention of E. coli transmission include: handwashing, improved sanitation in drinking water, thoroughly cooking meat and avoiding consumption of raw, unpasteurized beverages, such as juices and milk, and avoidance of cross-contamination of utensils and work spaces when preparing food.

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