Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Facultative intracellular pathogens are microorganisms that can live both inside and outside host cells. They adapt to various environments, allowing them to evade the immune system and cause disease.
5 Must Know Facts For Your Next Test
Facultative intracellular pathogens can switch between an intracellular and extracellular lifestyle depending on environmental conditions.
These pathogens include bacteria like Mycobacterium tuberculosis and Salmonella enterica.
They often use specialized mechanisms to enter host cells, such as secretion systems or surface proteins.
Surviving within host cells allows these pathogens to hide from the host's immune system.
Facultative intracellular pathogens can manipulate host cell functions to create a more favorable environment for their survival and replication.
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Related terms
Obligate Intracellular Pathogens: Microorganisms that must live within a host cell to survive and replicate.
Secretion Systems: Molecular systems used by some bacteria to inject proteins into host cells, facilitating infection.