E. coli Bacteria
Escherichia coli or E. coli bacteria are one of the many types of bacteria that inhabit the digestive system of humans and animals. Most strains of E. coli that reside within organisms are harmless and even provide beneficial functions within their host. These bacteria aid in food digestion, nutrient absorption, and produce vitamin K. Some strains of E. coli however, have gained the ability to produce poisonous substance which cause disease. These pathogenic strains can cause intestinal disease, urinary tract infections, and meningitis. Other pathogenic strains cause disease, not through the use of toxins, but by invading and damaging the walls of the intestines.
Pathogenic E. coli
Some harmless E. coli bacteria acquire the ability to produce a toxin known as Shiga toxin. This toxin causes various symptoms in humans including severe abdominal pain, watery and bloody diarrhea, vomiting, and even kidney failure. Scientists have discovered that some harmless E. coli acquire the ability to produce Shiga toxin after being infected by a virus called a bacteriophage. Since a bacteriophage can transfer some of its viral genes to a bacterium, E. coli can acquire the Shiga toxin gene from bacteriophages containing the gene. The most common type of Shiga toxin-producing E. coli (STEC) in North America is known as E. coli O157:H7. This strain causes serious food poisoning in individuals who become infected.
In addition to STEC, other harmful types of E. coli include:
- Enterotoxigenic E. coli (ETEC) – toxin producing bacteria that cause the intestines to release excess fluid leading to what is commonly known as traveler’s diarrhea.
- Enteropathogenic E. coli (EPEC) – non-toxin producing bacteria that adhere to and colonize the intestinal wall. They are the major cause of infant diarrhea in developing countries.
- Enteroaggregative E. coli (EAEC) – adheres to and colonizes the intestinal wall in a ‘stacked-brick’ pattern. EAEC causes persistent diarrhea in children and adults.
- Enteroinvasive E. coli (EIEC) – invades the intestinal wall causing a form of dysentery with bloody diarrhea. These symptoms are similar to those seen with dysentery caused byShigella spp. bacteria.
- Diffusely adherent E. coli (DAEC) – the pathogenic ability of these bacteria is not fully understood.
E. coli Infection
Individuals that become infected with E. coli may experience various symptoms including severe abdominal pain, watery diarrhea, vomiting, nausea, and fatigue. E. coli have also been associated with some forms of urinary tract infection and can cause serious diseases such as neonatal meningitis and hemolytic uremic syndrome (HUS). HUS is a disease in which red blood cells are destroyed leading to anemia and kidney failure. Individuals may become infected with E. coli by eating or drinking contaminated food and water, through contact with people or animals that are infected, and by swallowing contaminated water when swimming in pools, lakes, and ponds. The CDC recommends that people avoid consuming unpasteurized food and drinks, under cooked meats, and contact with farm animals. Since E. coli is present in feces, it is important to properly wash your hands after using the toilet. Individuals should also wash vegetables and cooking utensils thoroughly during food preparation.
Genetically Engineered E. coli
Through genetic engineering, scientists are finding ways use E. coli to aid in the treatment of human disease. Genetic engineering involves transferring DNA from one cell to another. The new recombinant cell contains DNA and genes that are foreign to the original cell. This technique allows organisms, such as E. coli, to be used to produce different types of proteins. Scientists have used genetic engineering techniques to transfer genes that are needed to make insulin into E. coli bacteria. Insulin is a hormone produced by the pancreas to regulate blood glucose levels. The genetically modified E. coli have been able to produce insulin needed to treat patients with diabetes. Researchers have also successfully genetically engineered E. coli bacteria that seek out other disease causing bacteria and release enzymes that destroy them. These reprogrammed E. coli are even able to destroy bacterial biofilm, which is a slimy substance that protects bacteria from antibiotics, chemicals, and other substances or conditions that are hazardous to the microbes. E. coli have also been used in the production of antibiotics, vaccines, and have been engineered to target and deliver therapeutic drugs to cancer cells.
- Escherichia coli (E. coli). Centers for Disease Control and Prevention. Updated 08/03/2012 (http://www.cdc.gov/ecoli/general/index.html)
- What Is E. Coli? Medical News Today. Updated 05/21/2013 (http://www.medicalnewstoday.com/articles/68511.php)