BbITS clones are infectious for mice and acquired by feeding larval ticks.

a4 mice per wild-type or tagged strain were injected subcutaneously with 5×103 spirochetes.
bA blood sample was obtained from each mouse at 1 week post-inoculation and spirochete isolation attempted from ∼150 µl of blood.
cFisher's exact test comparisons indicated no significant differences between the number of mice infected by wild-type B31-A3 or by each BbITS.
dA blood sample was obtained from each mouse at 3 weeks post-inoculation and seroconversion assessed by immunoblot with B. burgdorferi whole cell lysates.
eCohorts of 6–8 larval ticks were fed to repletion on 2 infected mice per strain at 4 weeks post-inoculation and spirochete isolation attempted from individual ticks 10 days after feeding. NA; not attempted.