Cerebrospinal Fluid Analysis – Part 3 – CSF Stain and Culture, CSF electrophoresis
- The analysis is done on the CSF fluid.
- The most common stain use is the Gram stain.
- Gram stain gives a preliminary diagnosis.
- Gram stain will differentiate;
- Bacterial meningitis with the presence of bacteria whether it is cocci or bacilli and as gram-positive or negative.
- Viral meningitis will be negative.
- The most common causative agents are H.Influenzae in children and Neisseria and Streptococcus in adults.
Culture and Sensitivity
- Culture can identify the organism and the most common organism found are:
- Culture needs 24 to 48 hours to get a result. This may take up to 72 hours to get sensitivity.
Identification of Tuberculous bacilli:
- CSF and sputum smears are stained for the Acid-fast bacilli.
- These are red, rod-shaped bacteria.
- The conventional culture of the T bacilli takes 4 to 6 weeks of incubation.
- BACTEC method is a culture technique in which the growth medium for the culture of M.tuberculosis has added a substrate labeled with radioactive carbon. (14C).
- This substrate is used by the bacteria and produces radioactive carbon dioxide (14CO2), from the substrate.
- This 14CO2is detected and quantitated.
- This will give quick identification of mycobacteria.
- The polymerase chain reaction (PCR) method is also developed.
- This allows the amplification of genomes which can be detected by the genetic DNA probe.
- Mycobacterium is detected in 36 to 48 hours.
CSF protein electrophoresis
- Electrophoresis is done to find any abnormality of the proteins and immunoglobulins.
- This is helpful to diagnose:
- Multiple sclerosis.
- Autoimmune diseases.
- In Myelosclerosis typical findings are:
- Increased total proteins and this is mainly gamma globulins.
- There is a discrete sharp band in the gamma region called the oligoclonal band.
- The oligoclonal band may be seen in HIV.
- Electrophoresis differentiates CSF from serum, where is there is an extra band of transferrin in CSF and not in the serum.
Table of various type of meningitis:
|Disease||Pressure||Gross||Glucose mg/dL||Protein mg/dL||TLC count/mL||Type of Cells|
MN = Mononuclear cells.
TLC = Total leucocytic count.
Mening. = Meningitis.
Lympho = Lymphocytes.
Haem = Haemorrhage.