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Lung Bacteria Can Defend Against Pneumonia

LACTOBACILLUS has been shown to provide a barrier against Streptococcus pneumoniae colonisation in mice infected with the influenza A virus, providing new insights on how bacteria protect against invading pathogens.

Under a balanced host homeostasis condition, commensal microbes are known to provide a competitive barrier against invading bacterial pathogens in the intestinal tract, on the skin, or on the vaginal mucosa. Co-first author, Dr Soner Yildiz, University of Geneva, Geneva, Switzerland, explained that: “It is already well known how commensal bacteria in the gut fight off pathogens, but how lung bacteria, such as Lactobacillus, carry out this role is less clear.” For this reason, Dr Yildiz and his team studied the role of lung microbiota against Pneumococcus colonisation in mice and identified the bacteria Lactobacillus murinus to act as antimicrobials and immune system modulators in mouse lung tissue.

After exposing cultures of L. murinus to S. pneumoniae, results showed that L. murinus inhibited the growth of the pathogen through the release of lactic acid and reduced the extension of pneumococcal chains. Co-first author, João Pereira Bonifacio Lopes, added: “This antibacterial activity was not limited to S. pneumoniae, it also affected S. aureaus, the pathogen that can cause bloodstream, bone, and joint infections, as well as pneumonia.” The study also found that in mice treated with L. murinus following influenza A infection, the bacteria provided a barrier against pneumococcal colonisation.

Senior author Prof Mirco Schmolke commented: “This suggests that resident commensals in the lung could be applied as probiotics to counteract lung colonisation by pathogenic bacteria.” However, he further warned that additional studies are required before this can be explored as a potential treatment option in humans. “If it one day proves to be effective, the approach could improve the clinical outcomes for patients who are susceptible to respiratory tract infections,” he positively concluded.