A 40-year-old man develops a cough that is nonproductive and goes to see his family doctor. He says that he has been feeling "lousy" and has bronchitis, sinusitis, and a sore throat. The doctor orders an x-ray that does not show consolidation, but rather a patchy infiltrate in his upper right lung. The man denies taking any new pets or animals recently into his house. A Gram-stain of the sputum specimen shows a few Gram-negative rods that do not stain very well. Samples sent to the clinical laboratory do not grow on normal laboratory media (e.g., blood agar), but do grow i n monolayer cells in tissue culture. What bacterium is most likely to be the cause of this man's infection?