Final answer:
The most common cause of Malignant Otitis Externa (MOE) is Pseudomonas aeruginosa. MOE is an infection of the external ear canal that causes severe ear pain, drainage, and granulation tissue. It is more common in elderly diabetic patients.
Step-by-step explanation:
The most common cause of Malignant Otitis Externa (MOE), a serious infection of the ear seen in elderly diabetic patients, is Pseudomonas aeruginosa. MOE is an infection of the external ear canal that causes severe ear pain, drainage, and the formation of granulation tissue within the ear canal. It is often referred to as swimmer's ear. This infection is more common in elderly individuals with diabetes due to their compromised immune system and poor circulation which increases the risk of infection.