TABLE 1.
Infection and blockage rates in fleas that fed on blood containing wild-type or mutant Y. pestis strains
| Strain | No. of fleas blocked/no. of fleas analyzeda (%) | No. of fleas infected/no. of fleas analyzedb (%) | No. of CFU per infected flea (mean ± SE) |
|---|---|---|---|
| CO92p | 42/100 (42) | 16/20 (80) | (6 ± 1.8) × 104 |
| 11/77 (14) | 14/20 (70) | (1.4 ± 0.4) × 105 | |
| 15/101 (15) | 5/20 (25) | (5 ± 0.7) × 104 | |
| 42/104 (40) | 5/13 (38) | (1.7 ± 0.8) × 105 | |
| CO92ΔR1pe | 25/87 (29) | 8/11 (73) | (1.2 ± 0.6) × 104 |
| CO92ΔR2pe | 37/112 (33) | 19/20 (95) | (7.4 ± 0.7) × 105 |
| CO92ΔR3pe | 44/102 (43) | 5/16 (31) | (1.5 ± 0.6) × 105 |
| CO92ΔR4pe | 18/95 (19) | 11/20 (55) | (8.2 ± 2.2) × 104 |
| CO92ΔR5pe | 36/113 (32) | 11/20 (55) | (5.5 ± 0.8) × 105 |
| CO92ΔR6pe | 15/91 (18) | 9/20 (45) | (6.6 ± 2.8) × 104 |
| CO92ΔCDS1pe | 13/59 (22) | 11/19 (58) | (9 ± 2.6) × 104 |
| CO92ΔCDS2pe | 11/45 (24) | 10/17 (59) | (2.7 ± 1.4) × 105 |
a
Determined from samples of fleas during a 4-week period following the infectious blood meal.
b
Determined from samples of surviving fleas collected 4 weeks after the infectious blood meal.