E. Coli infection
Escherichia coli (E. coli) infection is caused by a gram-negative bacterium commonly found in the gastrointestinal tracts of humans and other mammals. While many strains of E. coli are harmless, certain pathogenic varieties can lead to serious health issues, including gastrointestinal distress characterized by symptoms such as stomach cramping, fever, and diarrhea that may be watery or bloody. These infections can also result in severe complications, particularly in vulnerable populations like children, due to conditions such as hemolytic-uremic syndrome (HUS), which can damage organs and blood cells.
E. coli infections can be classified into intestinal and extraintestinal diseases. Intestinal strains, such as enteropathogenic (EPEC) and enterohemorrhagic (EHEC) E. coli, are primarily responsible for foodborne illnesses, often transmitted through contaminated food sources. Extraintestinal strains, particularly uropathogenic E. coli, are a leading cause of urinary tract infections. Treatment approaches typically focus on managing symptoms and may include supportive care, antibiotics, and fluids, though increasing antibiotic resistance poses a significant challenge.
Preventative measures include proper food handling and hygiene practices, as well as improvements in water purification and sanitation. Ongoing research continues to explore effective treatments and strategies to control outbreaks, which still occur globally, emphasizing the importance of public health measures in mitigating risks associated with these bacterial infections.
E. Coli infection
ANATOMY OR SYSTEM AFFECTED: Blood, gastrointestinal system, intestines, nervous system, urinary system
DEFINITION: Infection by a gram-negative bacillus that normally colonizes the gastrointestinal tract of humans and other mammals
CAUSES: Bacterial infection
SYMPTOMS: Stomach cramping, fever, watery or bloody diarrhea, bowel wall inflammation, difficulty urinating, platelet and red blood cell destruction, organ damage
DURATION: Acute
TREATMENTS: None; symptom management and supportive therapy
Causes and Symptoms
Escherichia coli (E. coli) is a rod-shaped, gram-negative bacterium and a member of the Enterobacteriaceae family. Its cytoplasm is enclosed by an inner membrane, a periplasmic space, a peptidoglycan layer, an outer membrane, and, finally, a capsule. Most strains produce two types of projections, flagellae for and fimbriae (pili) for cellular and genetic transfer. There is no nucleus. The consists of a single circular chromosome that is usually complemented by multiple plasmids. There are no intracellular organelles, and respiratory processes occur at the cellular membrane.
E. coli are found as normal in the tracts of mammals and are the most common facultative anaerobes in the human intestinal tract. The traits that transform these benign inhabitants into disease-causing pathogens are called factors. The virulence factors of E. coli may be divided into adhesins, toxins, and capsules. Adhesins consist of fimbriae or outer proteins that allow the to bind to host cells and exert their disease-causing effects. Toxins are proteins made by E. colithat can be released to damage, or even kill, host cells. Capsules can enable the bacteria to elude the and invade host tissues.
Plasmids can be transmitted between various strains of E. coliand other bacteria by a process called conjugation. In order for a bacterium to conjugate, it must possess F (fertility) factor, which is a specific type of plasmid that contains genes for plasmid DNA and pili construction. A bacterium with F factor can use its F factor–generated pili to hold onto another bacterium and inject selected portions of genetic material into the bacterial partner. This genetic material can add new virulence factors or resistance attributes to the recipient bacterium.
The diseases caused by E. coli may be divided into intestinal and extraintestinal. TheE. colistrains causing intestinal diseases are of several different types. Enteropathogenic E. coli (EPEC) cause disease by adhering to intestinal epithelial cells with an outer membrane adhesin (intimin) and special pili, both of which are plasmid-mediated. The exact mechanism by which these virulence factors alter the intestine—resulting in watery diarrhea, low-grade fever, and vomiting—is unclear. Enterotoxigenic E. coli (ETEC) cause illness using a combination of mucosal adherence and production. The enterotoxin is similar to toxin and alters ionic transfer in the intestinal cells, producing copious amounts of watery diarrhea. The illness can vary greatly, from a lack of symptoms to severe with cramps, nausea, and dehydration. The adhesins and toxins appear to be mediated by both chromosomal and plasmid genes. Some E. colihave acquired genes from Shigella dysenteriae via conjugation, and these strains can produce Shiga toxins (STEC). The toxins permit intestinal invasion, resulting in painful, bloody diarrhea indistinguishable from shigellosis; such strains are referred to as enterohemorrhagic (EHEC). In about 5 percent of cases, Shiga toxins enter the bloodstream, causing damage to red blood cells, endothelial cells, and kidney cells; this is called the hemolytic-uremic syndrome (HUS). The life-threatening HUS is usually associated with the O157:H7 of E. coli and is seen more often in children than in adults. The O157:H7 strain often colonizes cattle, and humans may then acquire the infection from eating beef or fresh vegetables contaminated by cattle manure.
The extraintestinal diseases caused by E. colivary widely. E. coliis the most common cause of urinary tract infections (UTIs). The strains that cause UTIs are different from those strains that colonize healthy individuals. These uropathogenicE. coli possess fimbriae the bind to cells lining the urinary tract. They are also encapsulated and produce a toxin (hemolysin). The E. colimay ascend the urinary tract through the to the and kidney. The route is more common in women because of a shorter urethra and can be facilitated in both men and women by the use of a urinary catheter. Infection of the kidney can also occur via the bloodstream. E. coli infection can follow surgery, especially when the intestinal tract is violated. Surgical wound infection, abscesses, and are possible. Because ducts connect the gallbladder and directly with the intestinal lumen (cavity),E. coli often play a prominent role in and pancreatitis. Newborns with undeveloped immune systems may experience ear infections, bacteremia, or caused by E. coli. The strains producing neonatal meningitis have a K1 capsule, which may facilitate passage into the brain. Because E. coli are so common and possess many virulence factors, they can produce many additional types of infection.
Treatment and Therapy
Mild cases of diarrhea caused by EPEC strains usually can be managed with fluids and other supportive therapies, but the duration of illness may be made shorter with the use of antibiotic therapy. ETEC diarrhea is treated with loperamide and oral antibiotics. STEC and HUS are treated with supportive care. HUS may require renal dialysis.
Extraintestinal infection is treated by antibiotic therapy. Since E.coli are becoming increasingly resistant to antibiotics, susceptibility testing on the particular strain ofE. colicausing the infection, isolated from diagnostic cultures, must be performed. In 2022, scientists began using a combination of UV-C and blue-light to kill the bacteria. They found it to be particularly effective in combating a multidrug-resistant strain of E. coli.
Perspective and Prospects
Escherichia coli is named after Theodore Escherich, who described the bacterium in a paper published in 1885. Frederich Blattner of the University of Wisconsin completed the sequencing of the 4,288 genes of the E. coligenome in 1997. Nearly half of these genes were newly identified.
Epidemiological studies have assisted in the understanding of the origins of E. coliinfections. Intestinal illness can be prevented with improved farming methods, better food processing and handling, expanded sewage and facilities, purification of drinking water, and hand washing. The prevalence of hospital-acquired infections, such as UTIs, can be reduced by limiting the use of urinary catheters and the employment of closed drainage systems when catheters are necessary.
The treatment of extraintestinal E. coliinfection, and some intestinal infections, depends upon the use of one or more effective antibiotics. Resistance is a rapidly growing problem and can be controlled only through of the inappropriate use of antibiotics and the development of new agents.
Breakouts of E. coli still occur with regularity all over the world. In the United States, the Centers for Disease Control and Prevention (CDC) tracks these outbreaks and the efforts to curb them. In 2022, for example. E. coli was found on romaine lettuce in Wendy's restaurants in Michigan, Ohio, and Pennsylvania.
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