Table 1. Seeding activity assay and bioassay of test steel wires used as model carriers for prion disinfection.
| Seeding activity assay of test wires | Bioassay of test wires | |||||||
| Formulation/ | Concen- | Time | Tempera- | Residual seeding activity on test wires | Estimated residual infectivity | Estimated | Residual infectivity | Reduction of |
| Procedure | tration | [min] | ture [°C] | (as compared to the seeding activity | per wire | reduction of | per wire | infectivity |
| on reference wires) | [LD50i.c.imp] | infectivity [logs] | [LD50i.c.imp] | [logs]# | ||||
| Sodium hydroxide | 1.0 M | 60 | 23 | < SARW(10−8) | <3×10−2 | >7 | UD† | ≥5.5† |
| Sodium hypochlorite | 2.5% | 60 | 23 | ≲ SARW(10−8) | ≲3×10−2 | ≳ 7 | UD† | ≥5.5† |
| GdnSCN | 4.0 M | 10 | 23 | ≲ SARW(10−8) | ≲3×10−2 | ≳ 7 | UD¶ | ≥5.5¶ |
| SDS/NaOH | 0.2%/0.3% | 10 | 23 | < SARW(10−8) | <3×10−2 | >7 | UD† | ≥5.5† |
| 5 | 23 | ≲ SARW(10−8) | ≲3×10−2 | ≳ 7 | UD† | ≥5.5† | ||
| SDS/NaOH/ | 0.2%/0.3% | 10 | 23 | ≲ SARW(10−8) | ≲3×10−2 | ≳ 7 | UD‡ | ≥5.5‡ |
| n-Propanol | 20% | > SARW(10−8) to ≲ SARW(10−7) | >3×10−2 to ≲3×10−1 | >6 to ≲ 7 | ||||
| Alkaline cleaner | 1.0% | 60 | 23 | < SARW(10−8) | <3×10−2 | >7 | UD† | ≥5.5† |
| 0.5% | 10 | 55 | > SARW(10−7) to ≲ SARW(10−6) | >3×10−1 to ≲3×100 | ≳ 5 to <6 | >0 to ≤3×100 † | ≥5 to ≤5.5† | |
| 0.5% | 5 | 55 | > SARW(10−7) to ≲ SARW(10−6) | >3×10−1 to ≲3×100 | ≳ 5 to <6 | >0 to ≤3×100 † | ≥5 to ≤5.5† | |
| > SARW(10−6) to ≲ SARW(10−5) | >3×100 to ≲3×101 | ≳ 4 to <5 | >3×100 to ≤3×101 † | ≥4 to <5† | ||||
| Steam sterilization | 5 | 134 | ≈ SARW(10−6) | ≈3×100 | ≈ 5 | >0 to <3×100 † | >5 to <5.5† | |
| ≳ SARW(10−6) to < SARW(10−5) | ≳3×100 to <3×101 | >4 to ≲ 5 | ||||||
| SDS (pH 7.6) | 5% | 60 | 90 | ≳ SARW(10−6) to < SARW(10−5) | ≳3×100 to <3×101 | >4 to ≲ 5 | >3×100 to ≤3×101 † | ≥4 to <5† |
| Glutardialdehyde | 2% | 10 | 23 | > SARW(10−4) to ≲ SARW(10−3) | >3×102 to ≲3×103 | ≳2 to <3 | ≈3×103¶ | ≈ 2¶ |
| (neutral., pH 7.0) | ||||||||
| Glutardialdehyde | 2% | 10 | 23 | ≳ SARW(10−3) to < SARW(10−2) | ≳3×103 to <3×104 | >1 to ≲ 2 | >3×103 to <3×104¶ | >1 to <2¶ |
| non-neutral., pH 4.6) | ||||||||
| Cidex OPA | 0.55% | 10 | 23 | > SARW(10−3) to < SARW(10−2) | >3×103 to <3×104 | >1 to <2 | >3×103 to <3×104¶ | >1 to <2¶ |
| Peracetic Acid | 0.25% | 60 | 23 | > SARW(10−2) to < SARW(10−1) | >3×104 to <3×105 | >0 to <1 | >3×104 to ≤3×105 † | ≥0 to <1† |
Test wires contaminated with 10−1-diluted 263K scrapie brain homogenate carried an initial infectivity load of approximately 3×105 LD50i.c.imp/wire, and reference wires contaminated with 10−1-, 10−2-, 10−3-, 10−4, 10−5-, 10−6, 10−7- and 10−8-diluted 263K scrapie brain homogenate carried 3×105-, 3×104-, 3×103-, 3×102-, 3×101-, 3×100-, 3×10−1- or 3×10−2 LD50i.c.imp/wire, respectively [29]. Reduction of prion infectivity on test wires is expressed in log10 units (logs). Explanation of abbreviations: neutrl. – neutralized; UD - undetectable. Explanation of symbols:
#
Test limit of bioassay for titre reduction: 5.5 logs [29];