What is the most common organism responsible for otitis externa?

The most common organism responsible for otitis externa is Pseudomonas aeruginosa. This organism is particularly well-known for its role in various infections, especially in cases of external ear infections, also referred to as swimmer's ear. Pseudomonas aeruginosa thrives in moist environments and is often associated with water exposure, which makes it a prevalent cause of otitis externa in individuals who frequently swim or have wet ears.

The characteristics of Pseudomonas, such as its ability to form biofilms and resistance to many common antibiotics, further contribute to its prevalence as a causative agent in otitis externa. In addition, Pseudomonas is a Gram-negative bacteria known for its distinct green pigment and fruity odor, which can be observed in infected ear discharge.

While other organisms, such as certain species of Streptococcus and Proteus, as well as fungi like Aspergillus, can contribute to ear infections, they are less commonly the primary pathogens in typical cases of otitis externa when compared to Pseudomonas aeruginosa.