Table 5. Effect of residual formaldehyde in tissue from guinea pigs on the growth of Bacillus anthracis Sterne in study of inactivation of bacterial Tier I Select Agents*.
| Tissue type, no. samples | Fixation time, d | Incubation time for tissue in PBS/water | Sample inactivation† | Positive control |
|---|---|---|---|---|
| Skin, 2 | 2 | 45 min | –/– | +/+ |
| Skin, 2 | 14 | 45 min | –/– | +/+ |
| Skin, 2 | 21 | 45 min | –/– | +/+ |
| Ears, 2 | 2 | 45 min | –/– | +/+ |
| Ears, 2 | 14 | 45 min | –/– | –/– |
| Ears, 2 | 21 | 45 min | –/– | –/– |
| Spleen, 3 | 2 | 45 min | –/– | +/+ |
| Spleen, 3 | 17 | 45 min | –/– | –/– |
| Spleen, 3 | 17 | 24 h | –/– | +/+ |
| Liver, 3 | 2 | 45min | –/– | +/+ |
| Liver, 3 | 17 | 45 min | –/– | +/+‡ |
| Liver, 3 | 17 | 24 h | –/– | +/+ |
*Different fixation times (2, 14, 17, or 21 d) and wash times (45 min or 24 h) for skin, outer ear pinna, spleen, and liver result in the different ability of Sterne spores to germinate and grow in broth used for viability testing. +/− indicates presence and/or absence of growth in broth/on plates; PBS, phosphate-buffered saline. †50% of tissue tested. ‡Of 3 samples, 2 were positive for growth and 1 was inhibited by residual formaldehyde.