Bacterial findings in optimised sampling and characterisation of S. aureus in chronic rhinosinusitis

The bacterial spectrum in chronic rhinosinusitis (CRS) is clinically relevant. This study aimed to compare two sampling techniques and to characterise Staphylococcus aureus isolated from CRS patients. Bacterial specimens were collected from the nares and maxillary sinus in 42 CRS patients and from the nares in 57 healthy controls. Maxillary sinus sampling was performed in two ways in each patient: with a cotton-tipped aluminium swab through the enlarged sinus ostium, and with a protected brush. S. aureus was characterised by DNA-sequencing of the repeat region of the S. aureus protein A gene, spa typing. The protected brush technique was superior to the cotton-tipped aluminium swab in reducing contamination rate. However, the two sampling methods were consistent in terms of clinically relevant bacterial findings, and the easy-to-handle cotton-tipped swab can still be recommended when culturing the maxillary sinus. Patients showed a significantly higher presence of S. aureus in the nares compared with healthy controls, and healthy controls showed a significantly higher presence of coagulase-negative staphylococci in the nares compared with patients. The spa types were identical for the nares and maxillary sinus in all patients except one. The sampling techniques showed equivalent results, indicating a low risk of unnecessary antibiotic treatment when using the easy-to-handle cotton-tipped aluminium swab. The high rate of identical spa types of S. aureus isolated from the nares and maxillary sinus of CRS patients might indicate colonisation of the maxillary sinus from the nares.