Understanding Your Medical Test: A Patient Guide to Purpose, Sample Collection, and Results
A laboratory test that detects and identifies anaerobic bacteria in cerebrospinal fluid (CSF) to diagnose infections of the brain and spinal cord membranes.
{"This test looks for anaerobic bacteria that may cause serious brain or spinal cord infections","A sample of fluid is taken from around the spine using a lumbar puncture (spinal tap)","Results help doctors choose the right antibiotics to treat the infection","Anaerobic bacteria grow without oxygen and can cause severe infections if not treated"}
Key facts at a glance
- LOINC
- 87937-9
- Short code
- CSFAN
- Synonyms
- Bacteria CSF Anaerobe Cult
- Category
- chemistry
- Sample
- csf
- Container
- Sterile, leak-proof, screw-cap CSF collection tube or anaerobic transport vial; should be submitted in an anaerobic transport system to preserve viability of obligate anaerobes.
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- anaerobic-culture
- CPT
- 87075
- SNOMED
- 396685001
- Specimen volume
- Minimum 1-2 mL of CSF; ideally 2-5 mL collected into separate sterile tubes (Tube 1 for chemistry, Tube 2/3 for microbiology). Larger volumes increase recovery of organisms in CNS infections.
- Stability
- Specimen should be transported to the laboratory immediately at room temperature (do not refrigerate, as cold may kill fragile anaerobes). Process within 1-2 hours of collection. If delay is unavoidable, store at room temperature in anaerobic transport medium for up to 24 hours.
- Hemolysis max
- 200
- TAT
- 72–336 hours
- Order
- routine
What is this test? This test is a laboratory examination that helps your healthcare provider learn important information about your health. It measures specific substances or markers in your body so your care team can screen for, diagnose, or monitor medical conditions.
The Anaerobic Bacteria Culture test is a laboratory procedure that analyzes your cerebrospinal fluid (CSF) to detect and identify anaerobic bacteria. Cerebrospinal fluid is the clear liquid that surrounds and protects your brain and spinal cord. Anaerobic bacteria are microorganisms that can grow and multiply without oxygen. These bacteria can sometimes cause serious infections in the nervous system, including meningitis (infection of the membranes surrounding the brain) and encephalitis (brain infection).
Why do I need this test? Your doctor may order this test as part of a routine checkup, to help find the cause of symptoms you are experiencing, or to follow an ongoing condition and see how well your current treatment is working over time.
Your doctor may order this test if you have symptoms suggesting a brain or spinal cord infection, such as severe headache, stiff neck, fever, confusion, or sensitivity to light. It is particularly important when standard bacterial cultures come back negative but your doctor still suspects a bacterial infection. Anaerobic bacteria are harder to detect than regular bacteria because they require special growth conditions without oxygen.
How is the sample collected? In most cases, a small sample of your blood is drawn from a vein in your arm by a trained healthcare professional, although some tests use a urine, swab, or other sample. The collection is quick, usually takes only a few minutes, and you can typically return to normal activities right away.
The sample is collected through a procedure called a lumbar puncture, commonly known as a spinal tap. During this procedure, you will lie on your side or sit up bent forward. A healthcare provider will clean your lower back with antiseptic and inject a local anesthetic to numb the area. Then, a thin needle is carefully inserted between the bones of your spine to collect a small amount of cerebrospinal fluid. The procedure usually takes about 15-30 minutes. You may be asked to lie flat for a while afterward to reduce the chance of a headache.
What do the results mean? Your results show whether your values fall within the normal reference range. A result outside that range does not always mean you have a serious problem, so your provider will interpret it together with your symptoms, medical history, and other findings before recommending next steps.
If anaerobic bacteria are found in your CSF, it confirms that you have a bacterial infection of the brain or spinal cord membranes. This is a serious condition that requires prompt treatment. If no bacteria are found, it could mean that your symptoms are caused by something else, such as a virus, fungus, or non-infectious condition. Your doctor will interpret these results together with your symptoms, physical examination, and other test results to determine the best treatment plan.
Reference range
No anaerobic bacteria isolated. Normal CSF is sterile; absence of anaerobic growth is the expected finding.N/A
No special patient preparation required. Specimen collection should be performed by a qualified healthcare professional using strict aseptic technique (e.g., lumbar puncture) to prevent contamination with skin flora. Discontinuation of antibiotics prior to culture is not recommended if clinically urgent, but should be documented if administered prior to collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Detecting anaerobic bacteria in cerebrospinal fluid is critical for diagnosing certain types of bacterial meningitis and brain abscesses. These infections can be life-threatening and require immediate antibiotic treatment. Anaerobic bacteria such as Bacteroides, Fusobacterium, and Clostridium species are common culprits. Identifying the specific bacteria helps doctors select the most effective antibiotics, as some anaerobes are resistant to certain drugs. This test is especially valuable when initial standard cultures fail to identify a cause for infection, as anaerobic bacteria require special culture conditions to grow.
Frequently asked questions
Is a lumbar puncture painful?
How long does it take to get results?
What happens if anaerobic bacteria are found?
Are there any risks to this test?
Sources
- 1
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- 3
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy