Escherichia coli, or E. coli, is a group of bacteria that belongs to the Enterobacteriaceae family. Most of this type of bacteria are normal inhabitants of the intestines, providing benefits to the health of the individual by preventing the growth of other harmful organisms. There are other Escherichia coli strains, however, that can often cause harm to the host. Infection with these harmful bacterial strains can often lead to gastroenteritis, meningitis in newborn babies, and urinary tract infections, among other illnesses.
In most cases, Escherichia coli can survive in the environment outside the human body. The feces of infected individuals usually contain the organisms. With improper disposal of waste, the organisms can contaminate drinking water and lead to widespread infections. Poor sanitary habits among food handlers can also lead to food contamination and infection. Person-to-person contact with infected individuals with poor health habits can also lead to E. coli infection.
There are five pathogenic, or harmful, strains of Escherichia coli which can cause gastrointestinal problems in people. They are Shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), and enteroaggregative E. coli (EAEC). Most of them are spread through ingestion of contaminated foods and water.
STEC can cause hemolytic uremic syndrome and hemorrhagic colitis in infected patients. These organisms produce a toxin inside the body which can lead to severe abdominal pain, diarrhea, vomiting, and fever. ETEC and EAEC, on the other hand, are the Escherichia coli strains which can cause travelers diarrhea, while EPEC can cause watery diarrhea. EIEC is more serious, leading to dysentery or bloody and mucoid diarrhea accompanied by pain, tenesmus, and dehydration.
Outside the intestines, Escherichia coli can invade the urinary tract, causing a urinary tract infection (UTI). In newborn babies, it can sometimes cause meningitis, which is often a serious condition. In rare cases, the organisms can reach the blood stream, causing bacteremia, which requires prompt medical attention. E. coli has been implicated in rare cases of pneumonia as well.
Escherichia coli growth can be isolated in the laboratory using stool samples from infected patients. Other laboratory tests are also available to detect presence of E. coli in stools, including the Enzyme-linked immunosorbent assay (ELISA) and the use of immunofluorescence microscopy. Bacterial infections are often treated using antibiotics, as well as with hydration and electrolyte replacement.