Bacterial differences linked to glucocorticoid treatment outcomes in chronic rhinosinusitis with nasal polyps

Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) exhibits distinct bacterial colonization patterns between eosinophilic (ECRSwNP) and non-eosinophilic (non-ECRSwNP) subgroups. It remains unclear to what extent these differences are clinically relevant to the response to glucocorticoid (GC) treatment. Objective: This study aimed to investigate differences in nasal bacterial colonization between ECRSwNP and non-ECRSwNP patients in relation to their GC treatment response. Methods: We enrolled 347 CRSwNP patients, including 222 ECRSwNP and 125 non-ECRSwNP patients. Nasal swabs were collected from all participants, and bacterial composition was assessed via standard culture techniques. Of these, 189 patients received a 2-week course of oral GC treatment (24 mg of methylprednisolone daily), and nasal bacterial colonization was analyzed in relation to GC treatment response. Results: Of the 347 CRSwNP patients recruited, Staphylococcus was the most prevalent bacterial genus, followed by Corynebacterium and Streptococcus . Compared to ECRSwNP patients, non-ECRSwNP patients exhibited higher colonization rates of Streptococcus viridans and Haemophilus influenzae , and lower colonization rates of Klebsiella . Among the 189 patients who received GC treatment, further subgroup analysis was performed based on GC sensitivity. In GC-sensitive patients, S. viridans and H. influenzae were significantly more prevalent in non-ECRSwNP than in ECRSwNP. Conversely, among GC-resistant patients, Corynebacterium pseudodiphtheriticum was increased considerably in ECRSwNP than in non-ECRSwNP. Conclusion: Our findings indicate that there are distinct bacterial compositions in non-ECRSwNP and ECRSwNP patients. Streptococcus viridans and H. influenzae are linked to GC-sensitive non-ECRSwNP, while C. pseudodiphtheriticum is associated with GC resistance in ECRSwNP, highlighting their potential role in modulating GC treatment outcomes.