What is the most common causative organism of malignant otitis externa?

Malignant otitis externa is typically associated with certain pathogenic organisms, and Pseudomonas aeruginosa is the most common causative organism. This type of infection often occurs in individuals with diabetes or immunocompromised states, leading to a severe and relentless infection that can extend into the surrounding structures of the skull.

Pseudomonas aeruginosa is known for its ability to thrive in moist environments, which makes it particularly adept at causing otitis externa, especially in warm and humid conditions. Additionally, its resistance to many antibiotics makes infections difficult to treat, further emphasizing its role in this serious condition. The pathogenic characteristics of this organism—such as its virulence factors, ability to form biofilms, and resistance mechanisms—contribute significantly to the severity often seen in cases of malignant otitis externa.

Other organisms listed, such as Staphylococcus aureus, Escherichia coli, and Streptococcus pneumoniae, have different associations with otitis externa or are more commonly implicated in less severe forms of ear infections.