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New research has identified a concerning characteristic in newborn babies that could significantly impact their health later in life.
Although some elements of the gut microbiome can be passed from mother to child in the uterus, a newborn’s gut was previously believed to be nearly sterile, with most bacteria acquired during birth or through breastfeeding.
However, new findings presented at the European Society of Clinical Microbiology and Infectious Diseases Global 2026 suggest otherwise.
Researchers analyzed stool samples from 105 infants admitted to a neonatal intensive care unit within the first 72 hours of life, aiming to capture the earliest stages of microbial and genetic exposure.
The study обнаружed antibiotic resistance genes (ARGs) — segments of DNA that enable bacteria to survive antibiotic treatment — in the newborns.
This could allow bacteria to evade antibiotics later in life, potentially making infections harder to treat.
Experts say the presence of these genes may be linked to the overuse or misuse of antibiotics, which can lead to resistance in mothers and potentially be transferred to babies during pregnancy.
The findings suggest that a newborn’s gut microbiome, influenced by maternal and environmental factors, may already be exposed to bacteria before birth.
Researchers also identified a range of genes linked to resistance against commonly used antibiotics, including those capable of breaking down widely prescribed medications.
“This finding suggests that a pattern of ARGs is already established at this stage,” said lead author Dr. Argyro Ftergioti in a press release.
“The neonatal gut harbors a diverse resistome, and the presence of clinically important ARGs so early in life is concerning,” she added.
The study further revealed links between resistance genes and several maternal and neonatal factors, including maternal hospitalization during pregnancy and the use of central venous catheters within the first 24 hours of life.
According to the researchers, the presence of antibiotic resistance genes before birth is largely shaped by maternal transmission — the transfer of microbes during pregnancy, labour or breastfeeding — as well as delivery conditions and early hospital exposure.
“Although some ARGs were expected, their high prevalence across the majority of samples was striking,” Ftergioti noted.
While gut bacteria in newborns play a crucial role in the development of the immune, digestive and nervous systems, maintaining a healthy microbiome is essential for protection against infections, allergies and chronic conditions such as asthma, attention-deficit/hyperactivity disorder and diabetes.
Earlier studies have also shown that newborns may host far more gut microbes than previously believed, including around 10,000 viral species — about ten times the number of bacterial species typically found in children.
“While further research is needed to understand how early carriage of resistance genes affects microbiome development and infection risk, these findings highlight the importance of surveillance, infection prevention and control in neonatal care,” Ftergioti said.
