[1] Johns Hopkins Univ, Sch Hyg & Publ Hlth, Dept Environm Hlth Sci, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Med, Baltimore, MD 21205 USA
[3] Roche Biosci, Palo Alto, CA 94304 USA
[4] Michigan State Univ, Dept Large Anim Sci, E Lansing, MI 48824 USA
[5] Hannover Med Sch, Inst Med Microbiol, D-30625 Hannover, Germany
[6] Natl Inst Dent & Craniofacial Res, Bethesda, MD 20892 USA
[7] Roche Mol Syst Inc, Alameda, CA 94501 USA