Positive CSF infectious agent test Positive mycobacterium CSF microscopy 2024-03-16T20:25:00Z The demonstration of mycobacterium by microscopy of the cerebrospinal fluid (CSF). Ziehl-Neelsen (Z-N) staining of cerebrospinal fluid (CSF) for acid-fast bacilli (AFB) is the cornerstone of the laboratory diagnosis of tuberculous meningitis (TBM). However, the sensitivity of conventional Z-N staining for the detection of AFB in CSF specimens is suboptimal.