Microbiological Profile and Antibiotic Susceptibility Patterns of Bacteria Isolated from Adult Patients with Chronic Rhinosinusitis

Background: In chronic rhinosinusitis, bacterial colonisation influences the inflammation. It is essential to know the microbial profile as well as the susceptibility to antibiotics in order to treat and reduce antibiotic resistance. Aims of the study: This research was done to establish the microbiologic spectrum of the bacteria in adult patients with chronic rhinosinusitis and to evaluate their susceptibility to antibiotics in relation to establishing the best treatment alternatives. Methodology: The case-control research was carried out between May 2025 and February 2026 in Iraq among 80 patients and 40 controls with CRS. Persistent >12 weeks symptoms were diagnosed with CRS. Nares swabs were aseptically collected and cultivated. Gram staining and biochemical tests were used to identify them. The Kirby-Bauer method was used to identify antibiotic susceptibility on Müller-Hinton agar, using antibiotics commonly used in Iraq, and interpreted based on guidelines. Result: No significant differences were found in terms of age, sex, BMI or smoking, whereas there was a significant increase in allergic rhinitis and major symptoms in patients with CRS. CRS exhibited much more positive cultures and single/mixed microbial isolates. The most common isolate was S. aureus, and there was a minor Gram-positive predominance. Gram-positive were very sensitive to vancomycin and linezolid whereas gram-negative were sensitive to carbapenems. The resistance to penicillin and other antibiotics that were commonly used was high, and it showed an increment in resistance. Conclusions: The chronic rhinosinusitis is characterized by a variety of bacterial pathogens, which are mainly Gram-positive ones. The observation of high efficacy of certain antibiotics is in contrast with significant resistance trends, especially in the case of frequently used medications, which highlights the significance of specific antimicrobial treatment according to the culture and susceptibility testing.