Gut Reactions

If our microbiotas are the metaphoric equivalent of forests, explains Stephanie Prescott (PhD `19)—complex environments with various interdependent species of plants and animals—antibiotics are like forest fires, wiping out the flora and fauna that creatures rely upon.

50%+

With rising C-section and Strep B rates, more than half of pregnant Americans take antibiotics prior to delivery

That’s the case with mouse pups born to mothers that were administered doses of commonly used antibiotics during gestation. But while the mouse mothers’ microbiota eventually returns to normal after just two to three doses of antibiotics, explains Prescott, changes to their babies’ microbiomes persist.

“Now that we know that this limited exposure to antibiotics makes a long-lasting difference in offspring,” says Prescott, two years into her National Institute for Nursing Research (NINR)-funded program at the National Institutes of Health, “we need to understand what difference the difference makes.”

"We're largely unaware of the long-term effects prophylactic antibiotics administered to pregnant women have on infants."

PhD student and NIH Fellow Stephanie Prescott, a long-time neonatal nurse

For her dissertation, Prescott is focused on the effects prophylactic antibiotics have on mouse pups’ likelihood of obesity, as well as their development of cancer, allergies, chronic inflammation, and their ability to withstand infection, as well as whether behaviors like breastfeeding mitigate these effects. It’s all part of work she’s doing with noted National Cancer Institute researcher Giorgio Trinchieri, who is focused on the role of inflammation and innate resistance, and the impact that microbiota have in cancer development, progression, and therapies to fight it.

Already, Prescott’s found that female pups exposed to antibiotics during gestation, and then raised on a Western diet (35 percent fat, 50 percent carbs, very little fiber), are 37 percent more likely to be obese than those from mothers not exposed to antibiotics. In addition, both male and female offspring had fattier, more inflamed livers. And while it’s too early advise limits on pregnant women’s exposure to antibiotics, Prescott—who also works as a neonatal nurse practitioner at INOVA Children’s Hospital—lately finds herself pausing before writing prescriptions for antibiotics, even as the vast majority of pregnant women receive antibiotics at least once, and more than 40 percent receive antibiotics immediately prior to delivery[1].

“I’m not ready to say that we shouldn’t prescribe antibiotics, because they do save lives,” she says. “But whenever we decide to do anything, there’s this cost-benefit analysis, and I think we’re largely unaware of the long-term effects prophylactic antibiotics administered to pregnant women have on infants.”

The work’s made Prescott appreciate the interplay between human beings and the bacteria living in and on us that assists with everything from digestion to immune function, an evolutionary language Prescott’s NINR mentor Wendy Henderson—herself an expert in digestive disorders—is fascinated by, too. As principal investigator for NINR's Division of Intramural Research, Henderson's also keenly invested in bringing voices like Prescott's to the research table.

“Training in these methods allows nurse scientists to know the language, and affects their perspective,” says Henderson. “Nurses have unique questions. Adding a nurse’s voice to this research has immense value.”

[1] Tejada, B. M. (2014). Antibiotic use and misuse during pregnancy and delivery: Benefits and risks. International Journal of Environmental Research and Public Health, 11, 7993-8009.