[1] Duke Univ, Med Ctr, Dept Med, Div Infect Dis, Durham, NC 27710 USA
[2] Duke Univ, Med Ctr, Duke Infect Control Outreach Network, Durham, NC USA
[3] Univ North Carolina Hlth Care, Dept Hosp Epidemiol, Chapel Hill, NC USA
[4] Univ N Carolina, Sch Med, Dept Med, Div Infect Dis, Chapel Hill, NC USA