An elderly man comes in with fever, chest discomfort, and a dry cough. His sputum culture grew bacteria on charcoal yeast extract agar. Which organism is most likely responsible?

Explanation

Legionella species are known to grow on charcoal yeast extract medium and commonly cause pneumonia with symptoms such as fever, chest pain, and dry cough, especially in elderly patients. Other bacteria listed do not typically grow on this specialized medium.