Treponemal strains reported in this study.

aOriginally provided by James N. Miller, University of California, Los Angeles, CA.
bStrain isolated in Seattle by Sheila A. Lukehart, University of Washington, Seattle, WA.
cStrains provided by Paul Hardy and Ellen Nell, Johns Hopkins University, Baltimore, MD.
dProvided by Sandra A. Larsen, Center for Disease Control and Prevention, Atlanta, GA.
eProvided by Peter Perine, Centers for Diseases Control and Prevention, Atlanta, GA.
fProvided by Robert George and Victoria Pope, Center for Disease Control and Prevention, Atlanta, GA.