In a cerebrospinal fluid analysis, which finding indicates viral meningitis?

The presence of a negative gram stain in cerebrospinal fluid (CSF) analysis is indicative of viral meningitis. In viral meningitis, the CSF may show a slight increase in white blood cells, typically lymphocytes, and the gram stain would not reveal any bacteria, which is essential for diagnosing bacterial meningitis.

A negative gram stain suggests that bacteria, which would be visualized if present, are not found in the CSF. This is significant because a positive gram stain usually points towards a bacterial infection. Therefore, a negative gram stain helps differentiate viral meningitis from bacterial meningitis, establishing a clearer clinical picture of the underlying cause of the meningitis.

While cloudy fluid and elevated protein levels might suggest an infection, they are not specific to viral meningitis. Increased glucose levels are also not characteristic of viral meningitis, as they typically remain normal or can be slightly decreased. Lastly, an elevated white blood cell count with bacteria present is a hallmark of bacterial meningitis rather than viral meningitis. Understanding these distinctions is crucial for proper diagnosis and treatment decisions.