Saliva-derived Limosilactobacillus fermentum SA1 alleviates Klebsiella pneumoniae pneumonia and modulates inflammasome-associated inflammatory responses and epithelial barrier integrity

Description

Klebsiella pneumoniae is a leading cause of hospital-acquired pneumonia, and the rise of carbapenem-resistant strains has made non-antibiotic preventive strategies an urgent priority. This study evaluated Limosilactobacillus fermentum SA1, a probiotic isolated from the saliva of healthy children, as a prophylactic against K. pneumoniae pneumonia. SA1 was identified by 16S rRNA sequencing and phylogenetic analysis, and tested against a clinical isolate (SSP5) and the reference strain ATCC 13883 in an A549-THP-1 epithelial-macrophage co-culture and a BALB/c intranasal infection model. SA1 tolerated gastric acid and bile, showed strong cell-surface hydrophobicity, co-aggregated with both pathogens, and inhibited their growth by 38% to 47%. It was non-haemolytic and showed a phenotypic antibiotic susceptibility profile broadly consistent with that reported for L. fermentum, although genome-based safety assessment is required to confirm strain-level safety. SA1 significantly reduced K. pneumoniae adhesion and invasion in both cell systems. Mechanistically, SA1 pre-treatment was associated with increased TLR2 expression, was associated with reduced expression of TLR4-, NF-κB-, and NLRP3-related inflammatory markers, lowered LDH release, an indicator of membrane damage/cytotoxicity, and rebalanced the inflammatory cytokine expression in A549-THP-1 co-culture system. In parallel, SA1 was associated with increased NRF2 and HO-1 expression and preserved the tight-junction proteins ZO-1, occludin, and claudin-1, maintaining transepithelial electrical resistance. In mice, prophylactic intranasal SA1 preserved body weight, reduced respiratory distress, and reduced the lung bacterial burden against both strains. These findings identify saliva-derived L. fermentum SA1 as a mechanistically defined, low-cost prophylactic candidate against K. pneumoniae pneumonia

Institutions

• National College, Trichy

  Tamil Nadu, Tiruchchirappalli

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