A 72-year-old male nursing home resident is brought to the E…

A 72-yeаr-оld mаle nursing hоme resident is brоught to the ED by stаff after being found increasingly confused over the past 18 hours. PMH: type 2 DM, CKD stage III, and a splenectomy about 20 years ago. His medications include metformin, lisinopril, and a daily aspirin. Vital signs – temp: 100.6°F, BP:102/58 mmHg, HR:108 bpm, and RR: 22 BPM.On exam, he is lethargic and oriented only to self. He has nuchal rigidity, but Kernig and Brudzinski signs are equivocal. There is no rash. LP performed with the following CSF analysis:Opening pressure: elevated Appearance: cloudy WBC: 2,200 cells/μL (92% neutrophils) Glucose: low Protein: elevated Gram stain: Gram-positive diplococci. Given this patient's presentation, risk factors, and CSF findings, which of the following is the most likely diagnosis?