Date: April 21, 2017
Subject: Regulatory Interpretation regarding surrogate strains which can be used to validate inactivation procedures
This is in response to your request, dated March 16, 2017 for a regulatory interpretation of the requirement which allows for the use of surrogate strains to validate inactivation procedures.
The select agent regulations provide that surrogate strains that are known to possess equivalent properties with respect to inactivation can be used to validate an inactivation procedure. However, the select agent regulations also provide that if there are known strain-to-strain variations in the resistance of a select agent to an inactivation procedure, then an inactivation procedure validated on a lesser resistant strain must also be validated on the more resistant strains. See, for example, 42 C.F.R. § 73.3 (d)(4).
For purposes of the requirement found in 42 C.F.R. §§ 73.3 and 4 (d)(4), 9 C.F.R. §§ 121.3 and 4 (d)(4), and 7 C.F.R. § 331.3 (d)(4),
- Viruses from the same family can be suitable surrogates for select agent viruses,
- Bacteria from the same genus can be suitable surrogates for select agent bacteria, and
- Any positive single stranded RNA can be suitable surrogates for regulated positive single stranded RNA.