FIG 1.
Detection of B. recurrentis spirochetemia in selected CC mouse lines by dark-field microscopy. Plasma samples collected daily from B. recurrentis A17-infected CC001 (A), CC019 (B), CC042 (C), CC046 (D), and CC058 (E) mice were examined by dark-field microscopy for 10 days postchallenge. Spirochete counts were determined by using a Petroff–Hauser counting chamber. The limit of detection of this approach is 2.50 × 105 spirochetes per ml of plasma. When means of day 1 and day 2 spirochetemic levels were compared within each mouse line, the significant difference was only detected for CC019 mice (P < 0.005; paired t test). When spirochetemic levels were compared between the five CC lines for each time point, the mean levels of CC001 and CC046 mice were significantly higher than those of CC0019, CC0042, and CC058 mice (P < 0.05; ANOVA).