TABLE 1.
Sampling efficiencies of three methods for removing culturable B. subtilis subsp. niger spores from surfacesa
| Sampling method | Trial | Sampling loss (%) | Processing loss (%) | Overall efficiency (%) |
|---|---|---|---|---|
| Swab kit | 1 | 1.3 | 29.8 | 68.9 |
| 2 | 2.5 | 18.3 | 79.2 | |
| 3 | 2.6 | 25.0 | 72.4 | |
| Mean ± SE | 2.1 ± 0.4 | 24.4 ± 3.3 | 73.5 ± 3.0 | |
| Cotton swab | 1 | 5.9 | 26.9 | 67.2 |
| 2 | 3.3 | 23.8 | 72.9 | |
| 3 | 12.5 | 21.7 | 65.8 | |
| Mean ± SE | 7.2 ± 2.7 | 24.1 ± 1.5 | 68.6 ± 2.2 | |
| Sponge swipe | 1 | 0.30 | 30.8 | 68.9 |
| 2 | 0.04 | 25.0 | 75.0 | |
| 3 | 0.01 | 21.1 | 78.9 | |
| Mean ± SE | 0.12 ± 0.09 | 25.6 ± 2.8 | 74.3 ± 2.9 |
a
Sterile glass petri dishes were each inoculated with 10 μl of a B. subtilis subsp. niger spore suspension containing 7.4 × 106 CFU, and the preparations were allowed to dry. The inoculated surfaces of the dishes were sampled by each method (n = 3), and the samples were processed and cultured on TSAC to determine the culturable concentrations of B. subtilis subsp. niger. The petri dishes were rinsed with buffer, and samples were cultured to determine the B. subtilis subsp. niger concentrations remaining in the dishes after surface sampling. Percent loss and overall efficiency values were calculated from the data (see text).