- Stool culture negative for routine enteric pathogens (Salmonella, Shigella, Campylobacter, E. coli 0157:H7) and Clostridium difficile toxin. Recent successful treatment for Clostridium difficile does not exclude a patient if toxin now absent. However, the patient must be a minimum of 5 weeks from the time treatment was started at the time toxin is absent.