Here is another example of an acute meningitis from bacterial infection. Note how the sulci are obscured by the exudate. A sample of cerebrospinal fluid (CSF) can be obtained via lumbar puncture, if there is no papilledema to indicate the intracranial pressure is too high to safely perform this procedure. The CSF in such cases typically has a low glucose, high protein, and a high cell count with many PMN's. A gram stain should be done to aid in identification of bacterial organisms. The lactate dehydrogenase (LD) is increased with bacterial meningitis but not with viral meningitis.