A 57-year old man has been in the hospital in New York City on a ventilator for 3 days when he developed a severe pneumonia characterized by grossly bloody sputum. The doctors immediately started him on cephalosporin, a broad spectrum antibiotic, and send a sputum sample to the lab for identification. The test comes back showing a Gram negative coccobacilli resistant to all of the β-lactams, including cephalosporins, fluoroquinolones, aminoglycosides, and the carbapenems. The doctors begin to treat the pneumonia aggressively with a new antibiotic, tigecycline. Fortunately, the patient responds to treatment and begins to improve. What is the most likely cause of the man’s nosocomially acquired pneumonia? What is one other cause of pneumonia?