Which condition involves inflammation and/or infection of the external auditory canal and is treated with antibiotics?

The condition that specifically involves inflammation and/or infection of the external auditory canal is known as otitis externa, commonly referred to as swimmer's ear. This condition typically occurs when water remains trapped in the ear canal, leading to bacterial growth. Symptoms include itching, redness, swelling, and pain in the ear. Treatment often involves the use of antibiotics to combat the infection, and sometimes corticosteroids are prescribed to reduce inflammation.

The other conditions mentioned do not primarily affect the external auditory canal or are treated differently. Cholesteatoma, for example, is a type of skin growth in the middle ear that can lead to more serious complications and often requires surgical intervention rather than just antibiotic therapy. Serous otitis media, on the other hand, refers to fluid buildup in the middle ear without infection and is generally treated with observation or other non-antibiotic measures. Thus, the treatment approach for otitis externa specifically aligns with the use of antibiotics, making it the correct answer.