Mr. ABC, 70-yrs-old with long-standing type 2 DM presents with C/O pain in the left ear with purulent drainage. On examination, he is afebrile. Pinna of left ear is tender, external auditory canal is swollen and edematous. WBC count is normal. The organism most likely to grow from the drainage is:

P. aeruginosa Ear pain and drainage in an elderly diabetic patient must raise concern about malignant external otitis. The swelling and inflammation of the external auditory meatus strongly suggest this diagnosis. This infection usually occurs in older diabetics and is almost always caused by P. aeruginosa.