Escherichia coli (E. coli) are Gram negative enteric bacteria that live in the human gut. Its presence in nature is an indication of human feacal pollution. E. coli also causes human disease such as urinary tract infections and neonatal meningitis. Infection with particular enterotoxigenic strains can lead to life threatening intestinal diseases. E. coli are distinguished immunologically by serotyping based on three types of antigen: the somatic or O antigen which corresponds to terminal sugars on the cell surface lipopolysaccharide, the capsular or K antigens and the flagellar or H antigens.