Swimmer's ear, a form of external otitis is commonly caused by which organism?

• A. Acinetobacter baurnannii
• B. Bordetella bronchiseptica
• C. Haemophilus influenzae
• D. Pseudomonas aeruginosa

Answer: (D)

Pseudomonas aeruginosa is the organism most classically linked to swimmer’s ear. External otitis tends to occur after moisture exposure to the ear canal, especially in swimmers, and Pseudomonas thrives in moist environments and on damaged skin. This Gram-negative, oxidase-positive, non-fermenting rod is an opportunistic pathogen of the external canal, readily colonizing moist skin and producing biofilms and inflammatory toxins that drive the pain and discharge of otitis externa. Its association with water exposure and its prevalence as a cause of non-severe but persistent external ear infections make it the best answer.

Acinetobacter baumannii is more commonly an agent of hospital-acquired infections and wound or pneumonia cases. Bordetella bronchiseptica is primarily an animal respiratory pathogen and occasional zoonotic human pathogen. Haemophilus influenzae can cause ear infections, but it is a more typical cause of otitis media rather than swimmer’s ear.