Studies in mice have shown that Lactobacillus in the lungs provided a barrier to Streptococcus pneumoniae colonization after infection with influenza A virus and treatment.Streptococcus pneumoniae can cause severe pneumonia, especially in elderly patients.Given the rise of antibiotic resistance, these findings suggest that probiotics may provide an alternative treatment for bacterial lung infections.

In healthy organisms, "symbiotic" bacteria that live in the host without damaging the host provide a competitive barrier to invading bacterial pathogens.Co-first author Soner Yildiz, a postdoctoral researcher at the University of Geneva in Switzerland, explains: "It is well known that symbiotic bacteria in the gut have the ability to fight pathogens.But how lung bacteria such as Lactobacillus do this is not clear."

To address this question, Yildiz and colleagues studied the effect of pulmonary microbiota on pneumococcal colonization in mice.The team had previously reported that healthy mice had plenty of Lactobacillus bacteria in their lung flora, which are known as antibacterial agents and immune system regulators.In the current study, they identified these symbiotic bacteria as L. Murinus, and further gene sequencing and microscopic examination showed that the bacteria were closely related to mouse lung tissue.

The team then exposed cultures of Listeria murine to Streptococcus pneumoniae.They found that Lactobacillus suppressed the growth of pathogens by releasing lactic acid.Co-first author Joao Pereira Bonifacio Lopes, PhD, said: "This antibacterial activity is not limited to Streptococcus pneumoniae.It also affects Staphylococcus aureus, a pathogen that can cause blood, bone and joint infections and pneumonia."

Finally, they treated mice with Lactobacillus after influenza A infection, and found that the bacteria provided a barrier to pneumococcal colonization in the animals."This suggests that the pulmonary symbiotic bacteria are resistant to the colonization of the lungs by pathogenic bacteria.However, further research is needed before it can be proven as a potential treatment.If it proves effective one day, it could improve clinical outcomes in patients at risk for respiratory infections."