What are the common microbiota found in the ear, skin, and upper respiratory tract?

Common Microbiota of the Ear, Skin, and Upper Respiratory Tract

Staphylococcus aureus is the primary microorganism that commonly colonizes all three anatomical sites—the ear, skin, and upper respiratory tract. 1

Primary Shared Organisms

Staphylococcus Species

• Staphylococcus aureus is explicitly identified as a pathogen common to infections of the middle ear (otitis media), skin and soft tissue infections, and upper respiratory tract infections. 1
• S. aureus causes acute otitis media less commonly than the primary otopathogens but is still a recognized bacterial cause. 1, 2
• Staphylococcus colonization in the nasopharynx may actually be beneficial rather than harmful, as increased abundance of Staphylococcus reduces the risk for acute otitis media complicating upper respiratory infections. 3
• In infections caused by exogenous pathogens (not part of oral flora) such as malignant otitis externa, mastoiditis, animal bites, trauma, and surgical complications, staphylococci are most frequently associated with these conditions affecting both ear and skin. 1

Other Shared Organisms

• Gram-negative bacilli are implicated in infections of the middle ear, mastoid, nasal sinuses, and are frequently associated with skin and soft tissue infections following trauma or surgical procedures. 1
• Pseudomonas aeruginosa is documented as a less common cause of acute otitis media and is associated with malignant otitis externa (an ear/skin interface infection). 1

Organisms NOT Common to All Three Sites

Upper Respiratory Tract and Ear Only (Not Typical Skin Flora)

• Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis are the most common bacterial causes of acute otitis media and upper respiratory tract infections, but these are not typical skin colonizers. 1, 4, 2
• These organisms represent oropharyngeal flora that can extend into the middle ear and sinuses. 1

Clinical Context and Pitfalls

Important Caveats

• The distinction between colonization and infection is critical—many organisms colonize these sites without causing disease. 3, 5
• Staphylococcus aureus found in primary ciliary dyskinesia patients affects both upper and lower airways, demonstrating its broad respiratory tract presence. 1
• When evaluating infections at these sites, consider that the same organism may behave differently depending on the anatomical location and host factors. 1, 6

Diagnostic Considerations

• Cultures from the pharynx or nasopharynx cannot accurately predict the causative organism of ear or sinus infections—direct sampling of the infected site is required. 1, 2
• Swabs are not the specimen of choice for ear or sinus infections; aspirated material or tissue is preferred. 1