Taking antibiotics while ill with the flu may increase the risk of developing bacterial pneumonia, according to new findings from researchers at Los Angeles-based Cedars-Sinai.
Researchers found that when influenza patients take antibiotics — which are meant to treat bacterial infections, not viral illness — it disrupts the gut's fungal microbiome. This disruption leads to a boost in eosinophils in the lungs. Eosinophils are immune cells that hinder the function of other cells responsible for clearing pathogens from the lungs.
In a mouse model study, those infected with the flu followed by a methicillin-resistant Staphylococcus aureus bacterial infection that were given antibiotics had greater lung damage and weight loss compared to the control group. Mice that received antibiotics also had higher levels of MRSA and bacteria in their lungs. Researchers also analyzed a cohort of flu patients at three U.S. medical centers, including Cedars-Sinai, and found an association between antibiotic use and higher levels of eosinophils, as well as longer lengths of stay and systemic inflammation.
Often, flu patients may continue taking antibiotics even after tests confirm they have a viral infection out of fear they will develop bacterial pneumonia, which is a common secondary infection in high-risk flu patients.
However, "this research demonstrates that prescribing antibiotics during influenza infections may do more harm than good," David Underhill, PhD, a co-author on the study and chair of the department of biomedical sciences at Cedars-Sinai, said in a news release. "This research also sheds light on the role that eosinophils play in regulating lung immunity."