FIG 6.

Disruption of bgp reduces the efficiency of joint colonization by B. burgdorferi in C3H/HeJ mice. Fourteen days after infection, mice were euthanized, and tissues were collected for DNA isolation and qPCR analysis of spirochete burden within joint tissues. Each point is representative of one mouse sample. Three/four mice for the WT and five mice for the mutant were used. (A) B31 5A4 spirochetes showed colonization of the joint in all mice at an inoculum dose as low as 100 B. burgdorferi spirochetes. (B) B31 A18 was less efficient at colonization as evidenced by 1 mouse remaining PCR negative at an inoculum of 100. (C) We failed to detect any spirochete DNA from mice infected with 100 bgpmut spirochetes, such that the difference between B31 5A4-100 and bgpmut-100 is statistically significant (P ≤ 0.05). At a higher inoculum (10⁴ spirochetes), joint colonization for the bgpmut strain was similar to that of the WT B31 A18-infected mice. (D) Only partial restoration of joint colonization was evident in the complemented strain, with 1/3 mice for all inoculums remaining PCR negative for B. burgdorferi DNA. Colonization by B31 A18 and complemented strains were comparable in the other 2/3 mice.