Table 2. Summary of early-phase (day 3 post-infection) in vitro mass transmission experiments.
| Y. pestis CFU/ml in infectious blood meal | Total # of Fleas | # of Fleas That Fed (%) | # of Obstructed Fleas | CFU Transmitted | Average CFU Transmitted per Flea | Post-Feed Flea Infection Rate and Mean Bacterial Load† | |
|---|---|---|---|---|---|---|---|
| O. montana infected with Y. pestis KIM6+ in mouse blood§ | |||||||
| Expt 1 | 1.5x109 | 212 | 124 (58.5%) | 4 | 38 | 0.84 | 36% (5.1x104) |
| Expt 2 | 2.8x108 | 147 | 132 (89.8%) | 5 | 0 | 0 | 10% (1.4x105) |
| Expt 3 | 4x108 | 213 | 136 (63.9%) | 4 | 0 | 0 | 35% (2.1x105) |
| Expt 4 | 1.9x108 | 210 | 173 (82.4%) | 2 | 1 | 0.01 | 65% (3.1x105) |
| Expt 5 | 1.1x109 | 270 | 132 (48.9%) | 10 | 0 | 0 | ND |
| Expt 6 | 1.9x109 | 187 | 144 (77.0%) | 1 | 8 | 0.22 | 25% (1.1x105) |
| Expt 7 | 1.4x109 | 205 | 202 (98.5%) | 3 | 7 | 0.09 | 40% (1.8x105) |
| Average | 9.7x108 | 206 | 149 (72%) | 4 | 8 | 0.17 | 37.6% (1.7x105) |
| O. montana infected with Y. pestis KIM6+ in rat blood | |||||||
| Expt 1 | 1.1x109 | 188 | 160 (85.1%) | 20 | 4476 | 27.98 | 100% (1.3x106) |
| Expt 2 | 8.5x108 | 183 | 157 (85.8%) | 16 | 1440 | 9.17 | 100% (1.2x106) |
| Expt 3 | 1.1x109 | 201 | 199 (99.0%) | 8 | 222 | 1.31 | 85% (1.5x106) |
| Expt 4 | 5.5x108 | 198 | 173 (87.4%) | 34 | 7210 | 41.68 | 100% (4.3x106) |
| Average | 8.9x108 | 195 | 172 (88%) | 20 | 3337 | 20.03* | 96.3%** (2.1x106) |
| O. montana infected with Y. pestis KIM6+ (ΔhmsR) in rat blood | |||||||
| Expt 1 | 1.8x109 | 203 | 180 (88.7%) | 14 | 84 | 0.85 | 55% (7.3x105) |
| Expt 2 | 7.0x108 | 189 | 143 (75.7%) | 6 | 12 | 0.17 | 50% (2.9x105) |
| Expt 3 | 8.0x108 | 190 | 163 (85.8%) | 2 | 7 | 0.17 | 25% (3.6x105) |
| Average | 1.1x109 | 194 | 162 (84%) | 7 | 34 | 0.4 | 43.3% (4.6x105) |
| X. cheopis infected with Y. pestis KIM6+ in mouse blood§ | |||||||
| Expt 1 | 1.1x109 | 456 | 139 (30.5%) | 0 | 59 | 0.42 | ND |
| Expt 2 | 1.0x109 | 199 | 103 (51.8%) | 0 | 0 | 0 | 100% (1.2x106) |
| Expt 3 | 9.0x108 | 205 | 156 (76.1%) | 0 | 5 | 0.03 | 95% (1.3x106) |
| Expt 4 | 4.9x108 | 180 | 148 (82.2%) | 0 | 164 | 1.23 | 90% (5.5x105) |
| Expt 5 | 3.6x108 | 204 | 153 (75.0%) | 0 | 7 | 0.05 | 95% (1.2x106) |
| Expt 6 | 2.0x109 | 198 | 145 (73.2%) | 0 | 0 | 0.00 | 85% (5x105) |
| Expt 7 | 2.5x108 | 202 | 148 (73.3%) | 0 | 0 | 0.00 | 100% (7.3x105) |
| Expt 8 | 3.2x108 | 201 | 113 (56.2%) | 0 | 28 | 0.26 | 95% (7.9x105) |
| Average | 8.0x108 | 231 | 138 (60%) | 0 | 33 | 0.22 | 94.3%** (9x105) |
| X. cheopis infected with Y. pestis KIM6+ in rat blood | |||||||
| Expt 1 | 1.1x109 | 203 | 152 (74.9%) | 48 | 51 | 0.45 | 75% (8.8x105) |
| Expt 2 | 1.1x109 | 203 | 107 (52.7%) | 14 | 0 | 0 | 80% (7.8x105) |
| Expt 3 | 2x109 | 199 | 135 (67.8%) | 30 | 71 | 0.53 | 100% (1.7x106) |
| Expt 4 | 9.7x108 | 210 | 129 (61.4%) | 39 | 287 | 2.78 | 80% (1.3x106) |
| Expt 5 | 8.8x108 | 205 | 114 (55.6%) | 47 | 123 | 1.14 | 95% (7.3x105) |
| Expt 6 | 7x108 | 209 | 135 (64.6%) | 43 | 0 | 0 | 75% (5.7x105) |
| Average | 1.1x109 | 205 | 129 (63%) | 37 | 89 | 0.82 | 84.2%** (1x106) |
ND = Not Determined
†All fleas sampled were infected on Day 0, n = 10–20
§Data from reference [6]
* p< 0.05 by Student’s t-test compared to X. cheopis rat blood group
**p< 0.0001 by chi-square test compared to O. montana mouse blood or rat blood (ΔhmsR) groups