Identification of Staphylococcus species in patients with chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a highly prevalent condition in otorhinolaryngology, representing a major public health issue due to its impact on morbidity, quality of life, and healthcare costs. Within the microbial context, the genus Staphylococcus plays a key role in modulating chronic inflammation. Although not considered a primary etiological agent, Staphylococcus aureus is frequently detected in CRS, and its ability to form biofilms and colonize intramucosal niches contributes to disease persistence. In contrast, coagulase-negative staphylococci (CoNS), while often associated with chronic infections, may exert protective functions in the nasal mucosa, particularly through antagonistic activity against S. aureus in the nutrient-competitive nasal cavity. This study investigated the presence and role of Staphylococcus species in CRS. Thirty-eight patients meeting EPOS 2020 diagnostic criteria were recruited during outpatient visits at the Rhinology Service, Hospital das Clínicas, Ribeirão Preto Medical School, University of São Paulo (HCFMRP-USP). Middle meatus samples were collected bilaterally using sterile Amies-moistened swabs under videoendoscopy. Swabs were plated on blood agar, and six representative colonies per phenotype were preserved, with three analyzed for Staphylococcus. Gram-positive cocci isolates were cultured on selective media (Baird Parker and mannitol salt agar) and subjected to tube coagulase testing with rabbit plasma-EDTA to differentiate coagulase-positive staphylococci (CoPS, suggestive of S. aureus) from CoNS. Of the 38 samples, 10.5% (n = 4) showed no bacterial growth, 7.9% (n = 3) were inconclusive, and 7.9% (n = 3) were negative for Staphylococcus. Among Staphylococcus-positive cultures (n = 28), S. aureus was detected in 67.9% (n = 19), CoNS in 57.1% (n = 16), and both species in 17.9% (n = 5). In total, 101 isolates suggestive of S. aureus and 49 of CoNS were recovered. The high prevalence of S. aureus in CRS supports its potential involvement in maintaining chronic inflammation via intramucosal colonization. The frequent detection of CoNS, including co-occurrence with S. aureus, suggests a modulatory or antagonistic role within the nasal microenvironment. Together, these findings indicate that both S. aureus and CoNS are widely distributed in CRS and may exert distinct yet complementary effects on disease pathophysiology.