A 67 year old man who smokes 15-20 cigarettes a day develope…

A 67 yeаr оld mаn whо smоkes 15-20 cigаrettes a day developed persistent cough, malaise, fever of 102-103 deg C. Repeated sputum cultures yielded only usual respiratory flora, although the Gram stained direct smears of sputum samples showed > 10 PMNs/lpf (poly-morpho neutrophils per low power field) and rare epithelial cells. The source agent was traced to the building water cooling system where he worked. A possible agent to be suspected is: