a 45-year-old man presents with a 3-day history of fever (t max-103.5°f), chills, anorexia, diarrhea, and a non-productive cough. on general examination, vitals are as follows: pulse- 98/min, rr- 24/min, bp-120/60mm hg, and t- 103.5 °f. there are coarse basal crepitations and scattered rhonchi on examination of the lungs. other systems exam are normal. chest x-ray (cxr) shows patchy alveolar infiltrates with consolidation in the lower lobe. complete blood count reveals leukocytosis; sputum gram stain reveals only a few polymorphonuclear (pmn) leukocytes and no predominant pathogens. question: what is the most likely diagnosis?