Cerebrospinal fluid (CSF) culture

  • Definition
    • A cerebrospinal fluid (CSF) culture is a laboratory test to look for bacteria, fungi, and viruses in the fluid that moves in the space around the spinal cord. CSF protects the brain and spinal cord from injury.

  • Alternative Names
    • Culture - CSF; Spinal fluid culture; CSF culture

  • How the Test is Performed
    • A sample of CSF is needed. This sample is usually done with a lumbar puncture, or a spinal tap.

      The sample is sent to the laboratory. There, it is placed in a special dish called a culture medium. Laboratory staff then observe if bacteria, fungi, or viruses grow in the dish. Growth means there is an infection.

  • How to Prepare for the Test
    • Follow instructions on how to prepare for a spinal tap.

  • Why the Test is Performed
    • Your health care provider may order this test if you have signs of an infection that affects the brain or nervous system. The test helps identify what is causing the infection. This will help your provider decide on the best treatment.

  • Normal Results
    • A normal result means no bacteria, viruses, or fungi grew in the laboratory dish. This is called a negative result. However, a normal result doesn't mean that there is no infection. The spinal tap and CSF smear may need to be done again.

  • What Abnormal Results Mean
    • Bacteria or other germs found in the sample may be a sign of meningitis. This is an infection of the membranes covering the brain and spinal cord. The infection can be caused by bacteria, fungi, or viruses.

  • Risks
    • A laboratory culture poses no risk to you. Your provider will tell you about the risks of a spinal tap.

  • References
    • Karcher DS, McPherson RA. Cerebrospinal, synovial, serous body fluids, and alternative specimens. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23d ed. Philadelphia, PA: Elsevier; 2017:chap 29.

      O'Connell TX. Cerebrospinal fluid evaluation. In: O'Connell TX, ed. Instant Work-Ups: A Clinical Guide to Medicine. 2nd ed. Philadelphia, PA: Elsevier; 2017:chap 9.