Figure 1.

Defects in the innate immune system affect the efficacy of doxycycline against Borrelia burgdorferi in vivo. C57BL/6 wild-type (WT) (n = 13), TLR2^–/– (n = 13), or MyD88^–/– (n = 10) mice were infected with B. burgdorferi N40 for 24 days and treated with 0.2% doxycycline in drinking water for 5 days. Ear punches were taken every day during treatment and cultured in Barbour-Stoenner-Kelly (BSK)–II media. Mice were sacrificed 2 days after the end of treatment and ear, joint, and heart were cultured in BSK-II media. Cultures were examined under dark-field microscope for about 2 weeks. The time to culture negativity was significantly different for C57BL/6 WT vs TLR2^–/– (P = .0017) but there was no significant difference between C57BL/6 WT and MyD88^–/– (P = .1916). P values were calculated using log-rank test.