Dolosigranulum pigrum Enhances Antibiotic Efficacy Against Staphylococcus aureus by Coordinating Host Immune Activation and Pathogen Metabolic Suppression

Staphylococcus aureus is a prevalent human pathobiont associated with chronic rhinosinusitis and skin and soft tissue infections, which are increasingly difficult to treat due to antimicrobial resistance and microbiota perturbation by antibiotics. Commensal bacteria have emerged as potential modulators of both host immune responses and pathogen pathogenesis. Prior studies indicate an inverse correlation between S. aureus colonization and the nasal commensal Dolosigranulum pigrum, yet the underlying mechanisms remain poorly understood. Here, using A549 Dual™ reporter cells, we demonstrate that commensals and pathobionts elicit distinct activation profiles of NF-?B and IRF signaling pathways and differential IL-8 production. In a humanized airway tissue model, D. pigrum improved antibiotic treatment to significantly reduce S. aureus survival while preserving barrier integrity and augmenting pro-inflammatory cytokine responses. However, heat-killed D. pigrum did not maintain this enhanced anti-S. aureus effect. Dual RNA-seq transcriptomic analysis revealed enrichment of host inflammatory pathways and reduction of S. aureus pathogenic potential during D. pigrum antibiotic adjuvant treatment in the airway tissue model. Furthermore, co-culture experiments revealed that D. pigrum constrains core metabolic pathways in S. aureus. Collectively, these findings demonstrate that D. pigrum limits S. aureus through both host immune modulation and direct suppression of bacterial pathogenesis and adaptive fitness, supporting its potential as a microbiota-based therapeutic adjuvant to enhance antibiotic efficacy against chronic airway infections.