Cerebrospinal Fluid (CSF)
Three to five milliliters of CFS is optimal for fungal investigation, however lesser volumes are often received and should be processed.
CSF specimens should be transported to the laboratory as soon as possible and processed promptly. If there is a delay do not refrigerate the samples, rather they should be left at room temperature or incubated at 30C. The specimen should be centrifuged. Keep the supernatant for cryptococcal antigen testing and process the sediment as follows.
- For direct microscopy use 1 drop of the sediment to make an India ink mount.
- Resuspend the remaining sediment in 1-2 ml of CSF and inoculate onto;
(a) Sabouraud's dextrose agar with chloramphenicol and gentamicin and incubate duplicate cultures at 26C and 35C; and
(b) Brain heart infusion agar (BHIA) supplemented with 5% sheep blood and incubate at 35C. Maintain cultures for at least 4 weeks.
Cultures from patients undergoing treatment for cryptococcal meningitis should be maintained for 3 months, so that dormant viable cells, which do not start to grow until after a one month period, will not be missed.