[1] Vanderbilt Univ, Sch Med, Med Ctr N A3310, Dept Med,Div Infect Dis, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Sch Med, Dept Pathol, Nashville, TN 37232 USA
[3] Vet Affairs Med Ctr, Nashville, TN 37212 USA
[4] Univ Zurich Hosp, Div Gastroenterol, CH-8091 Zurich, Switzerland