The patient's symptoms (fever, neck stiffness, severe headache, photophobia) are classic for meningeal irritation. The CSF analysis provides key diagnostic clues:

The patient's symptoms (fever, neck stiffness, severe headache, photophobia) are classic for meningeal irritation. The CSF analysis provides key diagnostic clues:

• Increased opening pressure: Common in bacterial meningitis.
• Neutrophilic pleocytosis: A hallmark of bacterial infection in the CSF, indicating a predominance of neutrophils (a type of white blood cell).
• Elevated protein: Bacteria consume glucose and release proteins, leading to higher protein levels.
• Low glucose: Bacteria consume glucose in the CSF, resulting in low glucose levels.

These findings are highly characteristic of bacterial meningitis.

The correct option is C.

$$\boxed{\text{C. Bacterial meningitis}}$$