Enteropathogenic Escherichia coli (EPEC)


Enteropathogenic Escherichia coli (EPEC) is a type of E. coli that causes diarrhea by adhering to intestinal cells and injecting effector proteins. It is a major cause of infantile diarrhea in developing and developed countries, and it does not produce toxin. EPEC is different from enterotoxigenic E. coli (ETEC), which is the leading cause of travelers` diarrhea and produces toxin.

EPEC can be classified into typical EPEC (tEPEC) and atypical EPEC (aEPEC) based on the presence of certain genes and plasmids. Typical EPEC have a plasmid called EAF (E. coli adherence factor) that encodes for bundle-forming pili (BFP), which are hair-like structures that help the bacteria to form microcolonies on the intestinal surface. Atypical EPEC lack this plasmid but have other adhesins that mediate attachment.

Both types of EPEC have a chromosomal pathogenicity island called LEE (locus of enterocyte effacement), which contains genes that encode for a type III secretion system (T3SS) and an adhesin called intimin. The T3SS allows the bacteria to inject proteins into the host cells, one of which is Tir (translocated intimin receptor), which acts as a receptor for intimin on the cell membrane. The binding of intimin to Tir leads to the formation of attaching and effacing (A/E) lesions, which are characterized by the destruction of the microvilli and the accumulation of actin beneath the bacteria. This results in malabsorption and diarrhea.

EPEC infection is mainly transmitted through the fecal-oral route, with contaminated hands, food, water or fomites as vehicles. Humans are the only source of typical EPEC, whereas atypical EPEC can also be found in animals. Person-to-person spread is common, especially among children in daycare centers or households.

EPEC infection affects primarily children younger than 2 years old, but can also cause sporadic diarrhea in adults. The symptoms include watery diarrhea, non-bloody stools, vomiting, fever and dehydration. The onset of disease may be as rapid as a few hours after ingestion of EPEC, and the duration may vary from a few days to several weeks. In some cases, persistent diarrhea may lead to malnutrition, growth retardation or death.

The diagnosis of EPEC infection is based on phenotypic or genotypic methods. Phenotypic methods involve detecting the A/E histopathology in intestinal biopsy specimens or cell cultures using fluorescence microscopy. Genotypic methods involve detecting the presence of specific genes or plasmids using DNA hybridization or PCR.

The treatment of EPEC infection consists of preventing dehydration by correcting fluid and electrolyte imbalances with oral or intravenous rehydration. Antibiotics may be useful in some cases, but resistance is common among EPEC strains. Other therapies such as bismuth subsalicylate or bovine anti-EPEC antibodies may also be helpful. There is no vaccine available for EPEC infection.

In conclusion, EPEC is an important cause of diarrhea in children and adults worldwide. It causes disease by attaching to intestinal cells and destroying their surface structure. It is transmitted through fecal-oral route and can cause severe dehydration and complications. It can be diagnosed by phenotypic or genotypic methods and treated by rehydration and antibiotics. Prevention of dehydration and correction of fluid and electrolyte imbalances are essential for managing EPEC infection.