Serious congenital infections are associated with which organism?

• A. Borrelia burgdorferi
• B. Borrelia recurrentis
• C. Treponema pallidum subsp. pallidum
• D. Treponema pallidum subsp. pertenue

Answer: (C)

Transplacental transmission of an infectious agent during pregnancy is the key idea for congenital infections. Treponema pallidum subsp. pallidum, the cause of syphilis, is classically linked to congenital syphilis. If a pregnant person has an active syphilis infection, the spirochetes can cross the placenta and infect the fetus, leading to a range of outcomes from early neonatal symptoms to long-term developmental and dental abnormalities if untreated. Screening and treating syphilis in pregnancy with penicillin prevents these congenital problems.

The other organisms listed are not associated with a typical congenital infection pattern. Borrelia burgdorferi causes Lyme disease and is not known for a well-established congenital syndrome, though rare transplacental transmission has been reported. Borrelia recurrentis causes relapsing fever transmitted by lice, again not a standard cause of congenital infection. Treponema pallidum subsp. pertenue causes yaws, a skin infection that is not transmitted congenitally.