Klebsiella pneumoniae (Kp) a common cause of
pneumonia leads to intense
lung injury and mortality that are correlated with infective exacerbations. Probiotics are a class of microorganisms that have immunomodulatory effects to benefit health. We investigated whether the probiotic Bifidobacterium longum 5(1A) induces protection in mice against lung
infection induced by Kp and the potential involved mechanisms. Kp
infection induced secretion of pro-inflammatory
cytokines, neutrophil recruitment, significant bacterial load in the lung and 50% lethality. However, treatment with live B.
longum 5(1A) induced faster resolution of
inflammation associated with an increased production of
IL-10, decreased lung damage with significantly reduction of bacterial burden that contributed to rescue 100% of mice from death. We found that these effects could be attributed, at least in part, to activation of the
Toll-like receptor (TLR) adapter
protein Mal, since B.
longum 5(1A) treatment in Mal-deficient infected mice did not show the protection observed in wild type infected mice. Thus, we propose that live B.
longum 5(1A) activates TLR-signaling pathway that results in ROS production and protects the host against
pneumonia-induced death by finely tuning the inflammatory response and contributing to faster return to lung homeostasis.