Challenging the gold standard: methods of sampling for microbial culture in patients with chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a highly prevalent multifactorial disorder. Culture-directed antibiotics are frequently prescribed to patients with CRS and the middle nasal meatus (MM) is traditionally believed to be a representative sampling site of the sinuses as a whole. The purpose of our study was to reevaluate the reliability of the MM as a sampling site in patients with CRS who suffer from impaired drainage from the sinuses to the MM.

Swabs and tissue biopsies were collected from the MM, maxillary sinus and frontal sinus from 50 patients with CRS. The results of bacterial culture were compared between sampling methods and sites in relation to the patency of the sinus ostia.

782 bacterial isolates were cultured from the samples. Concordant results between the MM and the sinus cavity were noted in 80% of patients for the maxillary sinus, but only 66% for the frontal sinus and 76% for the sinuses a whole. The differences were similarly prevalent in patients with open and occluded sinus ostia. Notably, swabs from all three sites provided representative information in 92% of patients and tissue biopsies did not provide additional information compared to multiple swabs.

The traditional method of sampling from the middle meatus provides inadequate information in 24% of patients with CRS, which may result in inadequate antibiotic therapy and contribute to increasing antibiotic resistance. Additional sampling from the sinuses should be recommended whenever possible, while invasive sampling is not necessary.