School of Medicine

Bloodstream infections in preemies may originate from their gut microbiomes

A new study from Washington University School of Medicine in St. Louis suggests that some dangerous bloodstream infections in premature infants may be caused by strains of bacteria already lurking in their gut microbiomes. (Photo: Getty Images)

Dangerous bacterial bloodstream infections in preemies may originate from the infants’ gut microbiomes, according to researchers at Washington University School of Medicine in St. Louis. Such infections are of substantial concern, as about half of infants who are extremely preterm or have very low birth weights experience at least one episode of the life-threatening infection after 72 hours of life.

The findings are published May 3 in the journal Science Translational Medicine.

Preterm infants are at high risk of infections due to underdeveloped organs, coupled with considerable antimicrobial exposure. Until recently, virtually every prematurely born baby was treated with antibiotics as a preventive measure. While the antibiotics are intended to target disease-causing pathogens, this treatment also can lead to disruption of the gut microbiome in a way that could allow virulent strains of antibiotic-resistant bacteria to increase in numbers.

“This is a vulnerable population,” said senior author Gautam Dantas, PhD, the Conan Professor of Laboratory and Genomic Medicine and a professor of pathology & immunology. “This is also a time when the composition of the gut microbiome is first developing. These early exposures to bacteria shape the gut microbiome in ways that will probably stay with these babies for the rest of their lives. We also have studied the gut microbiomes of infants born at full term, and we know that such babies do not have as many problems, but it’s clear that the type of bugs that colonize the gut in the first few months to three years of life will determine what the microbiome looks like later on. Our study also suggests that an early look at the gut microbiome in preemies may allow us to identify those at high risk of dangerous bloodstream infections.”

After birth, a baby’s microbiome develops by acquiring microbes from the environment and the infant’s primary caregivers. Such microbes help in a multitude of functions, including digestion and absorption of nutrients. In addition, in a more diverse gut microbiome, beneficial microbes outcompete disease-causing microbes, thereby protecting the infant from disease. In some instances, antibiotics can kill beneficial microbes, giving more dangerous and potentially antibiotic-resistant strains the opportunity to multiply and cause disease.

The most common bacteria in bloodstream infections are also commonly found to colonize the gut without initially causing disease. The researchers, including first author Drew J. Schwartz, MD, PhD, an assistant professor of pediatrics and an infectious diseases physician, aimed to test whether such bloodstream infections come from inside the gut or from external transmission. The study included newborns admitted to the neonatal intensive care units (NICU) at St. Louis Children’s Hospital, Children’s Hospital at Oklahoma University Medical Center and Norton Children’s Hospital in Louisville, Ky.

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