By Cara Murez 

HealthDay Reporter

THURSDAY, May 4, 2023 (HealthDay News) — About half of extremely preterm babies have at least one life-threatening bacterial infection in their bloodstream after 72 hours of life.

Now, new research points to the babies’ own gut microbiomes as the source.

Knowing that the most common bacteria in bloodstream infections are also commonly found to colonize the gut without causing disease at first, researchers set out to test whether the bloodstream infections came from the gut or from external transmission.

“This is a vulnerable population,” said senior study author Gautam Dantas, a professor of pathology & immunology at Washington University School of Medicine in St. Louis. “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.”

The investigators studied this in 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.

This included doing whole genome sequencing on the bacterial strain that was causing the bloodstream infection.

The researchers used computational profiling to precisely track the identical strain within feces so that they could also identify the strains of bacteria that had colonized the infants’ guts prior to their bloodstream infections.

The researchers found this theory that the bloodstream infections started in the gut to be true in 58% of cases, seeing a nearly identical disease-causing bacterial strain in the gut right before a bloodstream infection was diagnosed.

Some of the strains of bacteria that caused bloodstream infections were shared among the NICU infants, the study found.

Even in controlled environments there still could be an exchange of microbes, shared by hospital staff or transferred from NICU surfaces, the study authors explained.

Yet those who had bloodstream infections had dramatically more of the species causing it in their guts in the two weeks before the infection than did NICU infants who did not have infections, the study findings showed.

“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,” Dantas said in a university news release.

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

Babies born prematurely are at a high risk of infections because of underdeveloped organs, according to the researchers.

Nearly all preterm babies were treated with preventive antibiotics until recently. Yet, antibiotics can lead to disruption of the gut microbiome in a way that could allow virulent strains of antibiotic-resistant bacteria to increase in numbers.

Once born, a baby’s microbiome develops as it acquires microbes from the environment and caregivers.

Dantas said only infants who have confirmed bacterial infections should be given antibiotics.

“From this study, as well as in our lab’s past studies, it’s clear that we need to be better stewards of how antimicrobials are given,” Dantas said. “Antimicrobials are critical; we are going to need them to treat infections, but we need to carefully weigh whether and when to use antimicrobials in specific situations. We need to make sure that when those antimicrobials are given, we have a very good reason.”

More information

The U.S. National Institutes of Health has more on the microbiome.

SOURCE: Washington University School of Medicine in St. Louis, news release, May 3, 2023