[1] Univ Washington, Sch Med, Dept Microbiol, Seattle, WA 98195 USA
[2] Univ Washington, Sch Med, Dept Lab Med, Seattle, WA 98195 USA
[3] Texas A&M Univ Syst Hlth Sci Ctr, Dept Microbiol & Mol Pathogenesis, College Stn, TX USA
[4] Univ Calif Davis, Dept Med Microbiol & Immunol, Sch Med, Davis, CA 95616 USA
[5] Univ Massachusetts, Med Ctr, Dept Mol Genet & Microbiol, Worcester, MA 01655 USA