Escherichia coli (abbreviated as E. coli) are Gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia found in the environment, foods, and intestines of people and animals. E. coli are a large and diverse group of bacteria with many variants. Although most strains of E. coli are harmless, others can be extremely dangerous. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses.

Most types of E. coli are harmless and even help keep your digestive tract healthy. However, dangerous strains can cause infection if you eat contaminated food or drink fouled water. Contaminated foods, such as raw or undercooked ground meat products, raw milk, and contaminated raw vegetables and sprouts are the most common sources of dangerous infection. Prevention is best achieved through good hygiene, proper food safety, thorough cooking, and avoidance of cross-contamination.