The Incidence of Nosocomial Toxigenic Clostridium difficile Associated Diarrhea in Tehran Tertiary Medical Centers - Sadeghifard, Norakhoda; Salari, Mohammad Hossein; Ghassemi, Mohammad Raza; Eshraghi, Saeed; Amin Harati, Farzaneh (Acta Medica Iranica)