Research Suggests Taking Antibiotics During Influenza Infection Increases Risk of Developing Bacterial Pneumonia

New research led by Cedars-Sinai investigators indicates that “taking antibiotics during an influenza infection can be harmful and increases the risk of developing a bacterial pneumonia.”

Antibiotics are often prescribed for patients with respiratory illness, but the researchers say that antibiotics should be immediately stopped when “tests reveal that it is a virus,” such as influenza, is causing the illness. Antibiotics disturbed “the gut’s fungal microbiome” when influenza patients took them, resulting in an “increase in immune cells called eosinophils in the lungs that hinder the function of alveolar macrophages.” This chain of events “actually makes it more likely that a flu patient taking antibiotics will develop a bacterial pneumonia rather than avoid one.”

Investigators examined “laboratory mice that had been infected with influenza followed by a bacterial infection caused by MRSA (methicillin-resistant Staphylococcus aureus), one of the most common causes of a secondary bacterial pneumonia. One group of mice received antibiotics prior to the onset of a bacterial infection; the control group did not receive any medication.” Those treated with antibiotics “experienced greater weight loss and showed evidence of greater lung damage after MRSA infection. The mice that were given antibiotics also had higher levels of MRSA bacteria in their lungs and higher levels of immune cells (macrophages and eosinophils). In other words, this data suggests that antibiotic treatment during an influenza infection actually impaired the body’s efforts to clear the MRSA bacteria rather than helping the body heal.”

A cohort of influenza patients was also evaluated, and it was found that “eosinophils increase with antibiotic use and are associated with a higher length of stay and systemic inflammation.”