What organism is responsible for malignant external otitis?

Malignant external otitis is primarily caused by Pseudomonas aeruginosa, particularly in immunocompromised individuals or those with diabetes. This condition involves a severe and progressive infection of the external auditory canal, which may extend to surrounding tissues, including the temporomandibular joint and skull base.

Pseudomonas aeruginosa is a gram-negative, opportunistic pathogen that thrives in moist environments, making the ear canal a suitable site for infection. The organism is known for its ability to establish complex biofilms and exhibit resistance to various antimicrobial agents, which can complicate treatment.

Other organisms, such as Staphylococcus aureus, Escherichia coli, and Streptococcus pyogenes, can cause infections in the ear, but they are not typically associated with the severe, destructive nature of malignant external otitis that is characteristic of infections caused by Pseudomonas. Therefore, Pseudomonas aeruginosa is recognized as the principal pathogen responsible for this serious condition.