Microbial colonization of the sphenoid sinus with Enterobacterales and Staphylococcus aureus in patients undergoing endoscopic transsphenoidal surgery

Introduction The endoscopic endonasal transsphenoidal approach (EETA) is recognized as an effective and safe method for the resection of pituitary and sellar/suprasellar tumors. Classified as a clean-contaminated procedure, EETA entails intraoperative exposure to the nasal cavity, thereby introducing a potential risk of contamination with Staphylococcus aureus . The procedure also involves the sphenoid sinus - an anatomical region whose microbiological profile is poorly characterized in the current literature. Objective of the Study To determine microbial colonization patterns within the sphenoid sinus and their correlation with other anatomical sites for the preoperative identification of high-risk patients prior to EETA. Materials and Methods This prospective study included patients who underwent EETA between December 2024 and February 2025. All patients underwent microbiological testing of nasopharyngeal swabs, sphenoid sinus mucosa biopsies, gastrointestinal tract specimens, and endotracheal aspirates obtained via the endotracheal tube. Results A cohort of forty-one patients with a mean age of 61 years, was enrolled in this study. Microbial colonization of the sphenoid sinus was highly prevalent, detected in 90% of the analyzed mucosal biopsies. Gram-positive organisms (coagulase-negative staphylococci and Staphylococcus aureus ), all beta-lactam susceptible, were most frequent. Gram-negative Enterobacterales (26.8% of patients), including K. aerogenes, E. coli, E. cloacae complex, K. oxytoca, K. pneumoniae, M. morganii , exhibited significant resistance to penicillins (50%) and third-generation cephalosporins (30%). Conclusions These findings suggest that the current perioperative antibiotic prophylaxis regimen may be inadequate for a significant subset of patients. Consequently, a revision of antimicrobial prophylactic strategies is warranted, particularly for individuals undergoing EETA who present with identified risk factors for postoperative meningitis.