Chronic rhinosinusitis (CRS) is a multifactorial inflammatory condition of the paranasal sinuses, affecting approximately 10% of the global population¹. It is characterized by symptoms such as nasal congestion, facial pain, and hyposmia persisting for more than 12 weeks². CRS is often classified into two phenotypes: CRS with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP)³. Nasal polyps (NPs) are benign, edematous growths arising from the sinonasal mucosa, frequently associated with severe disease and higher recurrence rates⁴.

The pathogenesis of CRS and NPs involves a complex interplay of host immune responses, environmental factors, and microbial infections⁵. Microbial dysbiosis, characterized by an imbalance in the sinonasal microbiota, has been implicated in the persistence and severity of CRS⁶. Bacterial biofilms, particularly those formed by Staphylococcus aureus and Pseudomonas aeruginosa, are commonly observed in CRSwNP and are associated with resistance to conventional therapies⁷. Additionally, fungal elements, such as Aspergillus and Alternaria species, have been detected in NP tissues, suggesting a potential role in eosinophilic inflammation⁸.

Recent advances in molecular techniques, such as next-generation sequencing (NGS), have provided deeper insights into the microbial communities associated with CRS and NPs⁹. These studies have revealed a diverse microbiota, including aerobic and anaerobic bacteria, fungi, and viruses, which may contribute to disease progression¹⁰,¹¹. Understanding the microbiological aspects of CRS and NPs is essential for developing targeted antimicrobial therapies and improving patient outcomes.

This study aims to investigate the microbial profiles associated with CRS and NPs, focusing on bacterial and fungal colonization patterns, antibiotic resistance profiles, and their clinical implications. By elucidating the microbiological aspects of these conditions, we hope to contribute to the development of personalized treatment strategies.

A prospective observational study was conducted over 18 months at a tertiary care center. A total of 150 patients diagnosed with CRS, based on the European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) guidelines¹¹, were enrolled. Patients were divided into two groups: CRSwNP (n = 75) and CRSsNP (n = 75).

Inclusion Criteria:

• Adults aged 18–65 years.
• Persistent symptoms of CR
• (nasal obstruction, discharge, facial pain, or hyposmia) for >12 weeks.
• Confirmation of CRS or NPs via nasal endoscopy and computed tomography (CT) imaging.

Exclusion Criteria:

• Recent antibiotic or corticosteroid use within the past 4 weeks.
• Immunodeficiency or systemic diseases affecting the immune system.

History of sinonasal surgery within the past 6 months.

Sample Collection and Processing:

Nasal swabs and tissue samples were collected under sterile conditions during endoscopic sinus surgery. Samples were processed for bacterial culture, fungal culture, and molecular analysis using PCR and NGS. Antibiotic susceptibility testing was performed using the Kirby-Bauer disk diffusion method.

Statistical Analysis:

Data were analyzed using SPSS version 25.0. Microbial diversity and abundance were compared between groups using chi-square tests and ANOVA. P-values <0.05 were considered statistically significant.

Table 1: Microbial Distribution in CRSwNP vs. CRSsNP

Staphylococcus aureus was significantly more prevalent in CRSwNP (45%) compared to CRSsNP (20%) (p < 0.001).  Pseudomonas aeruginosa was more common in CRSwNP (15%) than in CRSsNP (10%), but the difference was not statistically significant (p = 0.32). Streptococcus pneumoniae was significantly more prevalent in CRSsNP (25%) than in CRSwNP (5%) (p < 0.001). Haemophilus influenzae was more common in CRSsNP (18%) than in CRSwNP (8%) (p = 0.04). Anaerobic bacteria were significantly more prevalent in CRSwNP (20%) compared to CRSsNP (5%) (p < 0.001).  Fungal colonization was significantly more common in CRSwNP (25%) than in CRSsNP (5%) (p < 0.001).

           Table 2: Prevalence of Staphylococcus aureus and Antibiotic Resistance Patterns

          Table 3: Fungal Colonization in CRSwNP

          Table 4: Correlation between Microbial Load and Disease Severity

          Table 5: Anaerobic Bacterial Isolates in CRSwNP

          Table 6: Antibiotic Susceptibility Profiles of Common Pathogens

Staphylococcus aureus was the most prevalent pathogen in CRSwNP (45%), with high resistance to methicillin (30%). Fungal colonization was observed in 25% of NP cases, primarily Aspergillus species. Anaerobic bacteria, such as Prevotella and Fusobacterium, were more common in CRSwNP than in CRSsNP.

The findings of this study provide significant insights into the microbiological landscape of chronic rhinosinusitis (CRS) with and without nasal polyps (NPs). The predominance of Staphylococcus aureus in CRSwNP aligns with previous studies, which have highlighted its role in biofilm formation and chronic inflammation¹². Biofilms are known to confer resistance to both antibiotics and host immune responses, contributing to the recalcitrant nature of CRSwNP¹³. The high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in our cohort (30% in CRSwNP) underscores the challenges in managing these patients and emphasizes the need for alternative therapeutic strategies, such as bacteriophage therapy or immunomodulators¹⁴.

Fungal colonization, particularly by Aspergillus fumigatus, was observed in 25% of CRSwNP cases, suggesting a potential role in eosinophilic inflammation and disease severity¹⁵. Fungi are known to trigger type 2 immune responses, which are characteristic of eosinophilic CRSwNP¹⁶. This finding supports the hypothesis that fungal elements may act as a persistent antigenic stimulus, driving chronic inflammation and polyp formation¹⁷. However, the clinical significance of fungal colonization remains debated, as some studies have failed to demonstrate a causal relationship between fungi and CRSwNP¹⁸. Further research is needed to elucidate the mechanisms underlying fungal-induced inflammation and its contribution to disease progression.

The higher prevalence of anaerobic bacteria, such as Prevotella and Fusobacterium species, in CRSwNP compared to CRSsNP suggests a potential role in tissue remodeling and polyp formation¹⁹. Anaerobes are known to produce proteolytic enzymes and toxins that can damage

mucosal tissues and promote inflammation²⁰. Additionally, the presence of anaerobic bacteria may contribute to the formation of biofilms, further complicating treatment²¹. These findings highlight the importance of considering anaerobic coverage when designing antimicrobial regimens for CRSwNP.

The distinct microbial profiles observed in CRSwNP and CRSsNP suggest that these phenotypes may represent different disease entities with unique pathogenic mechanisms²². For instance, the predominance of Streptococcus pneumoniae and Haemophilus influenzae in CRSsNP aligns with its classification as an infectious phenotype, while the microbial diversity in CRSwNP supports its characterization as a dysbiotic, inflammatory condition²³. These differences have important implications for treatment, as CRSwNP may require targeted antimicrobial therapy and immunomodulation, whereas CRSsNP may respond better to conventional antibiotics²⁴.

This study highlights the complex interplay between microbial colonization, host immune responses, and disease phenotype in CRS. The findings underscore the need for personalized treatment strategies that target specific pathogens and address the underlying dysbiosis. This study provides valuable insights into the microbiological aspects of CRS and NPs, revealing distinct microbial profiles associated with disease phenotypes. Personalized treatment strategies targeting specific pathogens may improve clinical outcomes and reduce recurrence rates.

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