[1] Univ Chicago Hosp & Clin, Dept Med, Chicago, IL 60637 USA
[2] Univ Chicago Hosp & Clin, Dept Surg, Chicago, IL 60637 USA
[3] Univ Chicago Hosp & Clin, Dept Pathol, Chicago, IL 60637 USA
[4] Univ Chicago Hosp & Clin, Infect Control Program, Chicago, IL 60637 USA