Escherichia coli is a gram-negative bacterium belonging to the Enterobacteriaceae family. More than 180 serotypes of this species have been described. E. coli is a symbiotic bacterium present in the intestine of humans and warm-blooded animals. It can also be found in soil and water, where it goes with the faeces. The presence of E. coli in water (so called Coli) is a common indicator of its pollution. The presence of Escherichia coli outside the digestive tract can lead to a variety of diseases, including peritonitis and urogenital tract infections. Particularly dangerous are the virulent strains of E. coli that produce toxins and/or are highly invasive. They can cause inflammation of the digestive system and diarrhea and cause septicemia. Young and immune-deficient organisms are especially susceptible to E. coli infection (colibacillosis). It is estimated that colibacillosis is responsible for up to half deaths of young animals.