The chronic maxillary sinusitis is multi-factorial as compared to the acute maxillary sinusitis. For instance, an inflammatory process may initiate the colonization of bacteria in some patients instead of the bacterial infection causing the inflammation. However, the principal pathogens causing the chronic form of the disease are bacteria.

Staphylococcus aureus, gram-negative enteric and anaerobes are the most common pathogens triggering chronic maxillary sinusitis in both adults and children. However, S. aureus, normally found in the nasal passages, is the main cause of the disease. S. aureus-associated sinus infections symptoms may be attributed to changes in the sinus mucosa or the bone beneath it. S. epidermidis contaminates the nasal cavity. Gram-negative rods commonly associated with chronic maxillary sinusitis include Escherichia coli, Enterobacter species, Proteus mirabilis, Klebsiella penumoniae and Pseudomonas aeruginosa.

The chronic sinusitis associated with S. pyogenes is more common in children than in the adults.  S. pyogenes is also a major cause of skin infections in children and bacterial pharyngitis.

Chronic maxillary sinusitis’ acute exacerbation involves a sudden change in condition of the patient due to development of new symptoms or worsening of the existing ones. However, microbiology in both acute exacerbation and baseline cases is quite similar. Gram-negative enteric and anerobes are the major cause of the acute exacerbation of the chronic maxillary sinusitis. However, some pathogens exclusively related to acute infections may also be present in case of acute exacerbations. The number of acute sinusitis aerobes may be high in the patients suffering from acute exacerbations of chronic maxillary sinusitis than in those having the baseline form of chronic maxillary sinus infections symptoms.

Recurrent and / or chronic bacterial infections may be found in the chronic maxillary sinusitis patients though the chronic condition is non-infectious.  Predominance of anaerobic bacteria growing in the oral flora is also found in chronic maxillary sinusitis and untreated subacute maxillary sinusitis. Chronic maxillary sinusitis patients also have polymicrobial infection that requires antibiotics for treatment.

Although clinical symptoms are absent in chronic maxillary sinusitis, facial pain, fever, headache or stuffiness in face may be felt some times. During chronic maxillary sinusitis, several polyps may form and epithelium may degenerate.  The maxillary sinus’ mucous membrane may change: atrophy or hyperplasia. Changes in the ostium may block the opening. Recent allergic sinusitis or viral infection of the upper respiratory tract may predispose you to chronic maxillary sinusitis.