Antibiotics May Make Newborns More Susceptible to Pneumonia, Researchers Say

Antibiotics May Make Newborns More Susceptible to Pneumonia, Researchers Say

Widespread use of antibiotics in newborns may interfere with gut bacteria, increasing the risk of the infants developing pneumonia, according to a study.

The research, “Intestinal Commensal Bacteria Mediate Lung Mucosal Immunity And Promote Resistance Of Newborn Mice To Infection,” was published in the journal Science Translational Medicine.

Most C-section deliveries in the United States are accompanied by an antibiotic prescription to the mother shortly before delivery. Up to 30% of newborns in neonatal intensive care units (NICUs) also get antibiotics.

Antibiotics are sometimes prescribed as a preventive measure, not because a baby has an infection. While they can stop bacterial infections that could be life-threatening to newborns, they also act on good bacteria that play an important role in immune-system development.

In fact, interactions between newborns’ immune system and intestinal bacteria influence how their immune system develops and works with other organs, including the lungs.

Researchers discovered that when mice were exposed to good bacteria immediately after birth, they developed a robust defense against bacterial pneumonia, the leading cause of death in infants.

When mice were deprived of the bacteria, their immune system’s development was faulty, and they were more susceptible to pneumonia. This situation was reversed by transferring good bacteria to their guts after birth.

Further experiments showed that good bacteria improved mice’s resistance to pneumonia by promoting the production of immune-system ILC3 cells. These cells travel to the lungs, where they produce a protein called IL-22. The protein protects against pneumonia during this developmental window.

The results support the idea that intestinal-bacteria colonization is crucial for the development of lung defenses in newborns. It also may explain why people with no genetic risk factors develop asthma or other lung diseases later in life, researchers said.

“It is time to begin pushing back on practices that were established decades ago, when our level of understanding was different,” Hitesh Deshmukh, MD, PhD, and senior author the study, said in a news release. “To prevent infection in one infant, we are exposing 200 infants to the unwanted effects of antibiotics. A more balanced, more nuanced approach is possible.”

If antibiotics are administered early and of short duration, infants may have time to replenish their gut bacteria. But Deshmukh said the process could take months and result in an abnormal mix of bacteria. Indeed, when a child becomes 1, the immune system’s development is complete, and any faults occurring during this period may become permanent.

Researchers plan to design a clinical study to investigate whether limited use of antibiotics by pregnant women and newborns may help prevent future infections in children.

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