TABLE 2.
Mean number of B. pertussis and B. parapertussis colonies recovered from swabs placed in serial 10-fold dilutionsa
|
B.
pertussis
|
B. parapertussis
|
||
|---|---|---|---|
| Concn of bacterial dilution (no. of bacteria/ml) | Colony no. recovered from five swabs (mean ± SD) | Concn of bacterial dilution (no. of bacteria/ml) | Colony no. recovered from five swabs (mean ± SD) |
| 1.4 × 105 | 395.0 ± 131.8 | 4 × 104 | 114.0 ± 15.5 |
| 1.4 × 104 | 27.6 ± 6.2 | 4 × 103 | 6.8 ± 1.3 |
| 1.4 × 103 | 4.8 ± 2.3 | 4 × 102 | 1.8 ± 0.8 |
| 1.4 × 102 | 0 | 4 × 101 | 0 |
a
Five swabs were placed into each of the dilutions for 2 min, removed, and streaked onto charcoal agar plates. The number of colonies on the plates was counted after a 2-day culture of B. parapertussis and after a 4-day culture of B. pertussis. For bacterial concentrations greater than 1.4 × 105 for B. pertussis and 4 × 104 for B. parapertussis, the numbers of colonies recovered from all the swabs were more than 1,000.