What is the primary bacterial cause of otitis externa?

The primary bacterial cause of otitis externa, commonly referred to as swimmer’s ear, is Pseudomonas aeruginosa. This organism is particularly associated with this condition due to its prevalence in moist environments, such as pools and lakes, and its ability to thrive in the external auditory canal, especially when there is a disruption of the skin barrier or excessive moisture.

Pseudomonas aeruginosa is a gram-negative bacillus that is known for its resistance to many antibiotics, making it a significant pathogen in various infections, particularly in cases of chronic otitis externa or in individuals with compromised immune systems. The presence of this bacterium in the ear canal can lead to inflammation, pain, and sometimes purulent discharge.

While other bacteria, such as Staphylococcus aureus and certain strains of Escherichia coli, can cause ear infections, they are more commonly associated with other types of ear infections or can be secondary pathogens rather than primary causes of otitis externa. Streptococcus pneumoniae, a common cause of otitis media, does not typically play a significant role in external ear infections. Therefore, understanding the role of Pseudomonas in otitis externa emphasizes the importance of proper ear care and hygiene, particularly in aquatic environments.