Virulence Properties of Shiga Toxin-Producing Escherichia coli Isolated from Cases of Bovine Mastitis in Brazil

Mastitis is a major problem in dairy farms and E. coli mastitis especially is a major disease in cows (1) because of the latter increasing incidence and severe symptoms (16). The concept of E. coli mastitis is that the organisms live in the environment and contaminate the teats probably as a result of fecal contamination (20). Shiga toxin-producing E. coli (STEC) isolates are an important group of food-borne pathogens that can cause severe gastrointestinal diseases in humans and complications such as the hemolytic uremic syndrome (HUS). The most often reported STEC serotype causing disease in humans worldwide is O157:H7, although many others have been described (31, 34, 42).