Germ-free animal

Germ-free animals are animals that have no microorganisms living in or on them. Such animals are raised within germ-free isolators in order to control their exposure to viral, bacterial or parasitic agents. When known strains of bacteria or microbiota are introduced to a germ-free animal, it usually referred to as a gnotobiotic animal, however technically speaking, germ-free animals are also gnotobiotic because the status of their microbial community is known.