When deriving axenic animals, microbiological monitoring should verify that which organism has not passed transplacentally to the pups?

• A. Salmonella spp.
• B. Mycoplasma spp.
• C. Escherichia coli
• D. Giardia spp.

Answer: (B)

Preventing congenital infection during derivation. In axenic (germ-free) derivation, a key concern is whether any maternal infection could be transmitted to the pups before or at birth. Mycoplasma spp. are particularly relevant here because they can inhabit the dam’s mucosal surfaces and have documented potential to cross the placental barrier, leading to a congenital infection in the offspring. They are also fastidious and may evade routine sterility checks, making targeted testing essential to confirm that pups are not born with the infection. Detecting and preventing transplacental transmission of Mycoplasma helps ensure truly axenic offspring.

Giardia, Salmonella, and Escherichia coli are not as routinely implicated in transplacental transfer to pups in standard axenic derivation protocols. Giardia is an intestinal parasite unlikely to cross the placenta. Salmonella and E. coli can cause systemic disease under certain conditions, but the focus for confirming axenicity and preventing congenital infection centers on Mycoplasma due to its ability to be transmitted congenitally and its detection challenges.