8 March 2017 - Futurity - Gut bacteria of preemies raise concerns about antibiotics

A new study of gut bacteria in premature infants highlights the problem of antibiotic resistance and stresses how extremely vulnerable these young patients can be.

The gut microbiome has emerged in recent years as a vital player in human health, affecting nutritional status, bone development, and immune function.

The new study warns that the microbes colonizing the gastrointestinal tracts of babies born prematurely are not health-promoting or even benign organisms, but close relatives of bacteria known to cause hospital-acquired infections, including Escherichia coli (E. coli), Klebsiella, and Enterobacter.

Researchers sequenced all of the DNA in the bacterial communities living in the preterm babies’ guts and identified almost 800 genes in these bacterial communities that confer resistance to antibiotics, about 80 percent of which had not previously been associated with antibiotic resistance.

“Our study demonstrates that even well-studied bacteria—the ones that we know cause disease or their close relatives—have many genes associated with antibiotic resistance that have not been characterized before,” says senior author Gautam Dantas, associate professor of pathology and immunology at Washington University in St. Louis.

“Premature babies do not always get bacterial infections that need treatment, but we have known for a long time that they are at higher risk for infection than babies born full term. Now, we know that preterm infant guts are attracting exactly the wrong kinds of bacteria.”

Because of this increased risk of infection, almost all preterm infants cared for in neonatal intensive care units (NICUs) receive antibiotics in the first two days of life, regardless of their health status. And a majority of those receive many more days of treatment.

“Extremely preterm infants often have multiple medical problems, with symptoms of prematurity overlapping with other conditions like infection,” says coauthor Barbara B. Warner, professor of pediatrics and neonatologist at St. Louis Children’s Hospital.

“The conventional wisdom has been antibiotics can’t hurt and they might help. But our new study demonstrates that wide-scale use of antibiotics in this population does not come without cost.”

The study, published in the journal Nature Microbiology, included babies cared for in the NICU of St. Louis Children’s Hospital, where the investigators collected 401 fecal samples from 84 preterm infants over the first three months of life. Sequencing all the bacterial DNA in these fecal samples identified resistance genes to 16 different antibiotics.

The babies that received antibiotics only in the first few days of life served as a comparison group to the babies that received antibiotics early plus subsequent treatments later. On average, the babies that continued receiving antibiotics had a total of 21 days of treatment. All babies were born before 33 weeks’ gestation.

In general, the findings suggest it is better to have a high diversity of bacterial species living in the gut.

Compared with babies born full term, preterm infants were found to have 10-fold fewer species of bacteria colonizing the gut. And among the preterm babies, those receiving the most antibiotics showed the least species diversity.

Giving breast milk was associated with increased bacterial diversity, as was each baby’s increasing age, perhaps simply from having more time for exposure.