The most common bacteria isolated from pediatric and adult patients with community-acquired acute purulent sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pyogenes.
Staphylococcus aureus and anaerobic bacteria (Prevotella and Porphyromonas, Fusobacterium, and Peptostreptococcus spp.) are the main isolates in chronic sinusitis.
Pseudomonas aeruginosa and other aerobic and facultative gram-negative rods are commonly isolated from patients with nosocomial sinusitis, the immunocompromised host, those with HIV infection, and cystic fibrosis.
