A 45-year-old man with poorly controlled type 2 diabetes mellitus presents to the emergency department with a 3-day history of fever, productive cough with purulent sputum, and progressive dyspnea. He reports feeling confused since this morning. Vital signs show temperature 39.2°C, heart rate 118/min, respiratory rate 28/min, and blood pressure 95/62 mmHg. Physical examination reveals crackles in bilateral lower lung fields. Laboratory studies reveal blood glucose 485 mg/dL, serum creatinine 2.1 mg/dL (baseline 0.9), and white blood cell count 16,500/μL. Chest radiograph demonstrates bilateral consolidative infiltrates with air bronchograms. Sputum culture yields mucoid, gram-negative rods that are oxidase-negative and ferment lactose. The organism forms a thick, gelatinous colony on culture media. Which of the following organisms is most likely responsible for this patient's pneumonia?

1. A)Pseudomonas aeruginosa
2. B)Serratia marcescens
3. C)Proteus mirabilis
4. D)Klebsiella pneumoniaeGABARITO
5. E)Enterobacter cloacae