The Role of Staphylococcus aureus Enterotoxins in Olfactory Dysfunction of Patients with Chronic Rhinosinusitis

Objectives: Recent studies suggest that Staphylococcus aureus and its enterotoxins (SEs) contribute to the pathophysiology of chronic rhinosinusitis (CRS). This study investigated the clinical significance of SE-specific IgE sensitization in olfactory dysfunction in patients with CRS. Methods: Seventy-five adult patients with CRS treated between July 2020 and December 2021 were enrolled. Serum SE-specific IgE levels against SEA, SEB, and TSST-1 were measured using the ImmunoCAP assay. SE sensitization was defined as a level ≥0.1 kU/L for at least one SE. Olfactory function was assessed using the Korean Version of the Sniffin’ Sticks test II (KVSS II). Total KVSS II and threshold, discrimination, and identification scores were compared between SE-specific IgE-positive and -negative groups. Correlations between individual SE-specific IgE levels and KVSS II scores were also analyzed. The primary comparison was the total KVSS II score; all other analyses were exploratory. Results: Among the 75 patients, 29 (38.7%) were sensitized to at least one SE. Compared with SE-specific IgE-negative patients, SE-specific IgE-positive patients showed a lower total KVSS II score, although the difference did not reach statistical significance (31.7 ± 10.6 vs. 26.2 ± 13.2, p = 0.09). SE-specific IgE positivity was associated with significantly poorer olfactory threshold performance (p = 0.01). Olfactory threshold scores were also significantly correlated with serum levels of SEA (r = −0.28, p = 0.02), SEB (r = −0.34, p < 0.01), and TSST-1 (r = −0.38, p < 0.01). In exploratory multivariable analysis, higher serum TSST-1-specific IgE levels showed a nominal association with lower olfactory threshold scores (B = −1.86; 95% CI, −3.60 to −0.13; p = 0.04), which did not remain statistically significant after Holm adjustment (adjusted p = 0.12). Conclusions: In this exploratory study, SE-specific IgE sensitization was associated with poorer olfactory threshold performance, whereas the primary comparison of the total olfactory score was not statistically significant. TSST-1-specific IgE showed a preliminary association that requires confirmation in larger prospective studies.