Table 2

Larval ticks artificially infected with ΔflaB mutants do not transmit the spirochetes to naive mice

B. burgdorferi clone in larval ticksNo. of mice infected/no. challengedaNo. of viable spirochetes per fed larvab
Wild type5/514,792 ± 6,033c
ΔflaB#4 mutant0/5811 ± 798
ΔflaB#6 mutant0/51,920 ± 1,893
  • a Approximately 200 artificially infected larvae were allowed to feed per C3H/HeN mouse. Mouse infectivity was determined by reisolation of B. burgdorferi from tissues from sacrificed mice.

  • b Spirochete burden was determined 7 days postrepletion by crushing individual ticks, plating, and counting CFU (average ± standard error of the mean; 4 or 5 positive ticks/strain). Results shown are representative of two independent assays.

  • c P = 0.029 (calculated by Student's t test) for wild-type to ΔflaB spirochete burden in the tick.