TABLE 3.

Infection doses for different F. tularensis strains in C57BL micea

StrainGenotypePhenotype or complementationNo. of CFU (lethal dose)b
FTT0918pilAFTT0086SubcutaneousIntraperitoneal
LVS1Δ93 bpLVS wt3 × 1071 × 101
LVS2Δ93 bpLVS wt1 × 1065 × 101
FSC688+Δ93 bpLVS2, pilA in cis5 × 1033 × 101
FSC741+LVS2, FTT0086 in cis2 × 106NT
FSC693+Δ93 bpLVS2, FTT0918 in cis<5c<5
FSC694++Δ93 bpLVS2, pilA and FTT0918 in cis<5<5
FSC200+++Type B wt<5<5
FSC767++FSC200, insertion mutation in FTT09182 × 102<5
  • a Mice in groups of five were infected subcutaneously. The result is from one single experiment representative of three experiments of similar design. wt, wild type; Δ, deletion; NT, not tested.

  • b The CFU value is a 50% lethal dose (LD50) calculation (26), but this should not be seen as a standard LD50 experiment since mice were sacrificed if they showed severe sickness. A lethal dose indicated as <5 CFU was used for strains where all animals showed lethal symptoms of infection for doses between two and five bacteria.

  • c The infection kinetics was delayed compared to that for the pilA/FTT0918 double complementation (Fig. 5).