Can Treponema pallidum be cultured in vitro?

• A. No, it cannot grow in vitro and must be cultured in rabbits
• B. Yes, it grows well in standard cell culture
• C. Only in organ culture
• D. It grows in soil culture

Answer: (A)

Some bacteria simply won’t grow in standard artificial culture because they depend on host factors to survive and replicate. Treponema pallidum is one of those organisms—it cannot be grown in ordinary in vitro media and requires a living host to propagate. Historically, it has been cultured by inoculating rabbit testes, which provide the necessary environment for its replication. Because of this, it cannot be reliably grown in standard cell culture or soil-based systems, making the rabbit model the traditional method for culturing it.