Which pathogen is most commonly associated with malignant otitis externa?

Malignant otitis externa is a severe and potentially life-threatening infection of the external ear canal, most commonly occurring in immunocompromised individuals, particularly those with diabetes mellitus. The pathogen most frequently associated with this condition is Pseudomonas aeruginosa.

This organism is a gram-negative bacillus known for its ability to thrive in moist environments and is often found in healthcare settings. It can cause various infections, particularly in individuals with compromised immune systems or underlying health conditions. In the context of malignant otitis externa, Pseudomonas aeruginosa leads to extensive soft tissue destruction and can invade surrounding structures such as the skull base, making it particularly dangerous if not treated promptly and effectively.

Other pathogens, while they may occasionally be implicated in ear infections, do not have the same prevalence in cases of malignant otitis externa as Pseudomonas aeruginosa. The ability of Pseudomonas to cause a rapidly progressing infection, along with its characteristic greenish-blue exudate and distinctive odor, further underscores its association with this serious condition. Therefore, understanding the microbiology of infections in immunocompromised patients is essential for diagnosis and management, making Pseudomonas aeruginosa the correct answer in this case.