BACKGROUND: Chronic rhinosinusitis (CRS) is a persistent inflammatory condition of the sinus mucosa. While Staphylococcus aureus has been shown to play a significant role in mucosal barrier disruption in CRS patients, coagulase-negative staphylococci (CoNS) such as Staphylococcus epidermidis and Staphylococcus lugdunensis are also implicated in CRS pathophysiology. This study investigates the effects of exoproteins secreted by planktonic and biofilm forms of clinical isolates of S. epidermidis and S. lugdunensis on the nasal epithelial barrier. METHODS: Thirty-one clinical isolates of CoNS were grown in planktonic and biofilm forms, and their exoproteins were concentrated. The epithelial barrier structure was assessed by measuring transepithelial electrical resistance (TEER) and the permeability of fluorescein isothiocyanate-dextran. Toxicity and inflammatory response were also studied. RESULTS: Our findings demonstrate that exoproteins from all planktonic forms of S. lugdunensis disrupted the mucosal barrier, whereas only nine of 16 biofilm-derived exoproteins had similar effects. Conversely, 11 of 15 exoproteins from planktonic S. epidermidis significantly disrupted barrier integrity
however, biofilm exoproteins did not. The study also showed that some exoproteins from planktonic S. epidermidis significantly reduced cell viability, while exoproteins from planktonic and biofilm forms of S. lugdunensis and biofilm S. epidermidis did not induce any statistically significant change in cell viability. Notably, four of 16 biofilm exoproteins from S. lugdunensis induced higher interleukin-6 (IL-6) secretion, whereas none of the S. epidermidis isolates showed a significant increase in IL-6 secretion. CONCLUSION: Our results suggest that CoNS exoproteins may contribute to CRS etiopathogenesis.