Antibiotic Use Reduces Gut Bacteria in Preterm Infants

The gut bacteria in prematurely born infants provide insight into antibacterial resistance and the vulnerability of the babies, according to findings published in Nature Microbiology.

Researchers from Washington University School in St. Louis sequenced DNA of the preterm infants’ microbiomes to understand how antibacterial therapies alter gut microbiota development.

The researchers used 401 stool samples from 84 infants in their study.

The study authors hypothesized that the babies would be susceptible to hospital acquired infections, like Escherichia coli (E. coli), Klebsiella, and Enterobacter while in the neonatal intensive care units (NICUs). Also, they believed most babies receive antibiotics within their first two days of life, regardless of their full term status.

“Extremely preterm infants often have multiple medical problems, with symptoms of prematurity overlapping with other conditions like infection,” study co author Barbara B. Warner, MD explained in a press release. “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 researchers determined that the babies had resistant genes to 16 different antibiotics in preterm babies given antibiotics in the first few days of life in addition to subsequent treatments following. Compared to full term babies, the preterm infants were discovered to have 10-fold fewer species of bacteria in their guts. The babies who received the most antibiotics showed the least amount of gut bacterial species diversity, the researchers reported. But, the researchers stressed, breast milk was linked to bacterial diversity, so as the babies aged, they may have simply had more exposure to various gut microbes.

The lowest gut bacteria species richness was found after use of such drugs like meropenem, cefotaxime, and ticarcillin-clavulanate. Related to the species most commonly found in gastrointestinal tracts, these antibiotics are used to treat the infections.

Meropenem was alarming to the researchers though, as they are part of a drug class called carbapenem, often considered a “last resort.” Most frequently, the preterm infants were administered vancomycin and gentamicin, which effected species richness.

“Consider what is going on in terms of selection pressure,” senior author Gautam Dantas, PhD said in the statement. “As with any antibiotic, giving carbapenems encourages the selection of bacteria resistant to this drug. And if these microbes, which dominate these babies' guts, become resistant to carbapenems, the microbes go on the highest urgency threat list at the Centers for Disease Control and Prevention.”