Escherichia coli O121 is a serotype of Escherichia coli, a species of bacteria that lives in the lower intestines of mammals.[1] The presence of many serotypes of E. coli in animals is beneficial or does not cause disease. However, E. coli O121 has been recognized as a potential disease causing serotype of bacteria. Unlike Escherichia coli O157:H7, another pathogenic serotype of E. coli, little is known about the public health significance of O121.
Escherichia coli O121 is also known as a type of "non-O157 Shiga toxin-producing E. coli" or "non-O157 STEC".