Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which media is typically used to culture cerebrospinal fluid (CSF)?

1. MacConkey, chocolate and sheep agar plate

2. Chocolate, sheep blood agar anaerobic SBAP

3. Mueller Hinton, chocolate agar and sheep blood agar

4. Thayer-Martin, chocolate agar, CNA

The correct answer is: Chocolate, sheep blood agar anaerobic SBAP

The media typically used to culture cerebrospinal fluid (CSF) is chocolate agar and sheep blood agar (often described as SBAP when used in anaerobic conditions). Chocolate agar is enriched with lysed red blood cells, providing additional nutrients that are crucial for the growth of fastidious organisms that may be present in CSF samples, such as Neisseria meningitidis and Haemophilus influenzae. Sheep blood agar also supports the growth of a wide range of bacteria and allows for hemolytic activity to be observed, which can be informative for identifying certain pathogens. The use of anaerobic conditions with sheep blood agar can be particularly important when there is a suspicion of anaerobic organisms in the CSF, although this is less common. However, the combination of chocolate and sheep blood agar is essential in creating an optimal environment for these potentially pathogenic organisms during a CSF culture. The other options include media that are either inappropriate for CSF culturing or do not provide the necessary environment for the growth of the key pathogens typically tested from CSF samples.