A colony carrying adventitious pathogens, or one that needs to be converted to microbiome-free status, must have its health status reset without losing the underlying genetic line.

Rederive the line via a custom germ-free protocol instead of trying to treat or clean up the existing colony directly: 1) Use in vitro fertilization (IVF) with donor animals sourced from the client's own colony, Taconic, or another commercial supplier. 2) Transfer resulting embryos into germ-free Swiss Webster pseudo-pregnant recipient females, which serve as reliable embryo recipients and foster mothers. 3) House recipients in germ-free isolators through birth and weaning, with ongoing microbial monitoring to confirm germ-free status is maintained. 4) Expect IVF-generated cohorts of roughly 10-40 mice of the same birth week per rederivation batch.