Table 2.

Loss of B. burgdorferi pathogenicity with in vitro passage in immunocompetent micea

MouseIsolateDay of sacrificeInfection (no. of specimens positive/no. examined)Arthritis (no. of mice with arthritis/no. examined)Carditis (no. of mice with carditis/no. examined)
BloodInoculation siteBladder
C3HcN40211/54/55/55/55/5
p22212/52/55/53/53/5
p51210/52/34/50/51/5
N40-75211/54/53/50/50/5
N40-75600/54/54/40/50/5
N40-75 (107)210/53/42/30/50/5
B6cN40210/55/55/50/55/5
N40-75210/53/54/50/50/5
  • ↵a C3H and B6 mice were infected with cN40 or its derivatives (p22, p51, and N40-75) obtained by in vitro culturing. Mice were infected with 104 spirochetes, unless otherwise indicated, and necropsied at 21 or 60 days after infection. Arthritis and carditis were assessed in a blinded fashion.