US costs and outcomes associated with Clostridium difficile infections: a systematic literature review, meta-analysis, and mathematical model. Issue 1 (December 2015) - Schweizer, ML; Nelson, R; Samore, M; Nelson, S; Khader, K; Chiang, H-Y; Chorazy, M; Herwaldt, L; Diekema, D; Blevins, A; Ward, M; Perencevich, E