Staphylococcus aureus and Staphylococcus lugdunensis Act in Concert to Disrupt the Nasal Epithelial Barrier

Chronic rhinosinusitis (CRS) pathophysiology and its link to microbiome is an area of ongoing investigation. Certain pathogens, in particular Staphylococcus aureus described to contribute to recalcitrant CRS. In addition, different species of coagulase negative staphylococci (CoNS) are frequently isolated from the sinonasal cavity of CRS patients. However, the influence of Staphylococcal species coexisting in the same niche on the inflammatory process remains unclear. The aim of this study was to explore the impact of exoproteins from various Staphylococcus species isolated from the same patients on the mucosal barrier.

Staphylococcal species isolated from CRS and control patients were cultured from sinus swabs in planktonic and biofilm forms, and their exoproteins extracted. Primary human nasal epithelial cells (HNECs) from CRS patients were cultured at an air-liquid interface (ALI) and exposed to 20 μg/mL exoproteins or control. Barrier disruption and cytotoxicity were assessed by measuring the transepithelial electrical resistance (TEER), passage of fluorescein labeled dextrans and lactate dehydrogenase (LDH) levels. IL- 6 concentration was measured employing ELISA. Patient's matched sinonasal tissue samples were analyzed with flow cytometry to detect and quantify immune cells.

Forty-four Staphylococcal species were isolated from 22 CRS and control patients including: 22 S. aureus, 12 S. epidermidis, and 10 S. lugdunensis. 15 out of 22 S. aureus exoproteins significantly enhanced cytotoxicity, reduced TEER values and increased paracellular permeability compared to control (p < 0.05). By contrast, S. epidermidis and S. lugdunensis exoproteins caused either mild or negligible effects on the TEER values, cell viability, and paracellular permeability. However, S. lugdunensis exoproteins induced significantly higher IL-6 compared to control. Correlation analysis indicated S. aureus and S. lugdunensis from the same patient acted in concert to disrupt the nasal epithelial barrier and induce toxicity.

This study shows the significant and detrimental impact of the presence of S. aureus exoproteins on nasal epithelial cell barrier function. S. aureus and S. lugdunensis isolated from the same patients acted in concert to affect the nasal barrier and inducing toxicity.