The risks bacterial infections pose to children and adults are well known and understood. In the brain, inflammation can kill cells and cause permanent brain damage. St. Jude researchers have now found evidence that the risk before birth is quite different.
Rather than inflammation and cell death, researchers showed that bacterial infections of the mother early in pregnancy led to production of too many neurons in the developing baby mouse brain. As a result, 50% more neurons were crowded into the region of the brain that accounts for thought, action and related functions. Similar crowding was also caused by treatment with certain antibiotics that kill bacteria by causing them to explode.
Neuronal crowding in the developing brain was associated with high levels of a protein, FoxG1, which is characteristic of autism. When the mice were tested three months after birth they showed below-average performance on tests for memory and other learning and thinking skills.
“Infections during pregnancy have been associated with cognitive and behavior disorders in children, but the cause was unknown,” said Elaine Tuomanen, MD, chair of the St. Jude Department of Infectious Diseases. “This study describes a possible explanation.”
The findings also raise questions about which type of antibiotics should be used to treat maternal infections.
The research appeared in the journal Cell Host & Microbe.