Escherichia coli O157:H7, Salmonella serotypes, Shigella sonnei, and Shigella flexneri are human pathogens and can cause serious disease. It has been reported that less than 100 cells of E. coli O157:H7 may cause infection. Shigella species also have a low infectious dose and are demonstrated hazards to laboratory personnel. Always use Biosafety Level 2 practices (at a minimum) and extreme caution when transferring and handling strains of these genera. Work in a biological safety cabinet when handling large amounts of cells. Disinfect or dispose of all plasticware and glassware that come in contact with the cultures in a safe manner.