What is E



What is E.coli 0157:H7?

E.coli is the abbreviation for the bacterium in the Family Enterobacteriaceae named Escherichia (Genus) coli (Species). Approximately 0.1% of the total bacteria within an adult’s intestines (on a Western diet) is represented by E.coli.

It is for this reason that the organisms, which inhabit the intestinal tract as normal flora, are named enteric bacteria. The Family to which E.coli belongs (Enterobacteriaceae is named what it is – because of the Greek word, enterikos, which pertains to the intestine and the name of the person who first isolated and characterized this bacterium, Escherich.

Are E.coli bacteria SAFE???

Yes, mostly. The presence of E.coli and other kinds of bacteria within our intestines is necessary for us to develop and operate properly, and for us to remain healthy – E.coli, along with other species of bacteria, provides us with many necessary vitamins. Bacteria make the vitamins, and we absorb them. We depend upon E.coli in our intestines as our source of Vitamin K and B-complex vitamins.

When are E.coli bacteria NOT SAFE?

Some bacteria are dangerous. We call such individual E.coli bacteria a different “strain” of bacteria within a given species. Some of these different strains (and there may be several within a given species) can be harmful to us. These individual strains of E.coli exist! This means that this particular individual strain of E.coli is genetically different than the vast majority of E.coli in our intestines. If this E.coli strain happens to have genetic information for producing harmful by product to us, we are in trouble. The rare strain of E.coli that is dangerous for us is E.coli O157:H7, a member of the EHEC-Enterohemorrhagic E-coli group. The term Enterohemorrhagic means an intestinally-related (from the Greek word enterikos) organism, which causes hemorrhaging –i.e., loss of blood.

How do we pick up this strain?

E.coli bacteria are everywhere in the environment. They are a common occupant of all animals. Anytime we eat something, drink something, or touch our hands to something that has been either a part of or has been near where animals are; there is always the potential to ingest these bacteria.

Where this strain of E.coli come from?

Bacterial cells are all over the place and it is possible for them to acquire genetic information form other sources (bacterial viruses, plasmids, or from pieces of DNA). In some cases, acquisition of this information may provide an advantage for survival. But E.coli O157: H7 appears to have been infected with a bacterial virus that had the ability to insert its own DNA into the bacteria’s chromosome without harming the bacterium. Every time this bacterial cell divided, the virus DNA, being now a part of the bacterial DNA, was passed on to every daughter cell-creating the E.coli strain, O157:H7…This virus’s genetic toxin (SLT), sometimes called, Vero toxin. Consequently, this strain of E.coli, and all of its progeny produced this toxin. This toxin is a protein which causes severe damage to intestinal epithelial cells (cells that line the wall of the intestine). We lose water and salts; blood vessels are damaged and bleeding occurs - hemorrhaging. A condition particularly dangerous to small children-even lethal. Children are too small to tolerate very much blood and fluid loss. For this reason, small children should not be allowed to become dehydrated, even in mild cases of diarrhea. In some cases, another syndrome is involved which is called hemolytic uremic syndrome (HUS), characterized by kidney failure and loss of red blood cells. Approximately 5% to 10% of small children progress to this stage of the disease, which is extremely dangerous to them, with a death rate of 3-5%. Fifty percent of children with HUS require dialysis during its episode. About 1000 children a year develop HUS. Eight percent of these patients will develop lifelong complications such as high blood pressure, seizures, blindness, bowel paralysis and kidney transplants or dialysis. This bacterium can also be very dangerous to the elderly or infirm. There can be a combination of HUS and other things, which involve the blood system. This can be lethal to the elderly in 50% of the cases. It’s called thrombotic thrombocytopenic purpura, a sort leakage of the blood vessels that feed nerve cells. The result is an encephalitis-like disease with psychosis, commas and seizures. 2-7% of E.coli O157:H7 can lead to TTP.

Totals Nationally

Food net calculations have determined that 76, 000, 000 cases of food borne illnesses occur each year with about 5000 deaths. Previous estimates were 33,000,000 cases and 9000 deaths. For E.coli there are approximately 73,000 cases with 61 deaths.

Incidences of Food Borne Illnesses per 100,000 persons

Pathogen 1996 1997 1998

Campylobacter 23.5 25.2 21.7

E.coli O157:H7 2.7 2.3 2.8

Listeria 0.5 0.5 0.5

Salmonella 14.5 13.6 12.4

Shigella 8.9 7.5 8.5

Vibrio 0.1 0.3 0.3

Yersinia 1.0 0.9 1.0

Totals 51.2 50.3 47.2

Some History on E.coli O157:H7

The toxin that O157:H7 has inherited is from its Shigella spp. that causes Shigellosis (bacillary dysentery). However O157:H7 produces tremendous amounts of the toxin. Shigellosis is very common in 3rd world countries. During the early 70’s Central and South America had an extensive and large epidemic of Shigellosis. It’s postulated that a safe E.coli became infected with the Shigella toxin during this outbreak. The first time O157:H7 was discovered and identified (named) was in the USA in 1975 from a person who had bloody diarrhea. In 1982 the first outbreak of O157:H7 occurred and at present has spread worldwide.

Are there other Dangerous E.coli?

Yes, depending on the resource material, there are between 60 to 170 other E.coli that have toxin capabilities. O111 is an example that’s found regularly in Australia that produces bloody diarrhea etc.

What does the O157:H7 stand for?

The different E.coli organisms are named after the antigen of their external protein make up. O157:H7 is an oblong organism with hair like projections labeled flagellates. The O157 refers to the body of the organism and the H7 refers to the flagellum. The laboratories at times have to enrich growth media, etc. to get an O157:H7 to produce the flagellates in order to identify the organism as O157: H7. When O157:H7 gets inhabited it often stops flagellum formation.

How does E.coli O157:H7 produce disease?

The E.coli harpoons the cells that line the intestine (epithelial) and attaches itself. The organism destroys the epithelial cells and start producing the Shiga or Vero Toxic Toxin, which is absorbed into the blood stream. The epithelia cells die and slough off the wall of the intestines, which allows for bleeding and diarrhea. The toxin that’s absorbed into the blood stream destroys the cells that line the blood vessels. The cells are called endothelial cells. This allows for hemorrhage in tissues through out the body. The toxin also causes blood cells to rupture and thrombocytopenia (loss of platelets)

Pulse Field Gel Electrophoresis (PFGE)

The cutting edge of technology is called Pulsed Field Gel Electrophoresis (PFGE), which relies on genetic fingerprinting to determine if different samples of E.coli are related.

E.coli bacteria from victims of an outbreak are cultured to increase their numbers. The bacteria’s DNA is chemically cut into small pieces, which are separated according to size.

A fluorescent dye illuminates the DNA under ultraviolet light, allowing scientist to compare different samples.

The PFGE process is only available in a handful states, but is expected to be more widely adapted in the coming years.

The Centers for Disease Control (CDC) has since established a database of the genetic fingerprints called Pulsenet, allowing public health officials from across the country to more easily identify and cope with E.coli outbreaks.

Ruminates

E-coli O157:H7 is a normal inhabitant of Ruminate (cud chewers) and does not cause illness in them. Therefore cattle, sheep, goats, deer, elk, antelope and so on are reservoirs of E.coli O157:H7. Contaminated meat and manure in the environment are sources of infection. As little as 10 organisms can cause the disease as oppose to a 1,000,000 needed for salmonella to cause disease. Cross contamination is a large factor in the spread. There is a certain percentage of the population of humans who have the organism but do not become ill. These people probably aren’t permanent carrier but temporary. These persons can be a serious source of infection to others especially if proper hand washing procedures aren’t followed after rest room visits. Animals that aren’t ruminates don’t appear to be a significant source of the disease as they are not natural carriers of the organism. They are artificially infected and naturally infected are transient carriers.

Levels of positive cattle

The Agriculture Research service published a study in March 2000 that indicated the percentage of cattle going to slaughter was as low as one percent in winter and up to twenty-eight percent in summer. In the study, sampled carcasses, forty-three percent of 341 carcasses were initially contaminated and after processing only six of three hundred thirty carcasses or 1.8% showed some level of contamination. This was one study and is not to be considered the national average.

Why don’t ruminates get sick from O157:H7?

Since the toxin of E.coli O157:H7 come from shagella spp. or at least identical to it we need to look at shagellosis in animals. We find that Shagellosis rarely occurs in animals and is a disease of humans and primates such as monkeys and chimpanzees. The organism is frequently found in water polluted with human feces. It kills about a million children per year in the third wold countries. While E.coli are normal to both ruminates and man, animals other than man and monkey and chimps are not in general susceptible to the Shigella toxin that is found in E.coli O157:H7.

This paper was taken from many sites on the internet; accuracy not guaranteed. This report is for information purposes only.

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