A boy presented with a history of fever, headache and vomiting since 3 days and disorientation since I day. On examination, neck rigidity was positive. He also had 1 episode of generalized tonic clonic seizures (GTC) and then he became unconscious. CECT was found to be normal. CSF examination reveals a cell count of 300 cells/mm3 (polymorphs: 50-70%), protein 70 mg/dL, sugar 50 mg/dL (blood: 95 mg/dL). Which of the following is the most likely diagnosis?