How to take samples for culture of cerebrospinal fluid?

Article written by MSc Tran Thi Vuong - Doctor of Microbiology - Laboratory Department - Vinmec Hai Phong International General Hospital

The cerebrospinal fluid has the following functions: protecting the central nervous system against mechanical trauma, ensuring the circulation of nerve fluids, hormones, antibodies and white blood cells, participating in pH regulation. and electrolyte balance of the central nervous system...
When the central nervous system is damaged, the cerebrospinal fluid will have corresponding changes. The examination of cerebrospinal fluid at this time will guide as well as help clinicians make a definite diagnosis.

CSF culture is for the purpose of isolating (identifying) the bacterial etiology as well as performing antibiotic susceptibility tests of the bacteria, thereby finding the right antibiotic for treatment. Therefore, if the doctor suspects that the patient has a central nervous system infection such as encephalitis, myelitis, especially meningitis, a CSF culture should be performed.
Symptoms related to the above diagnosis include: high fever, headache, stiff neck, vomiting or nausea, photophobia, impaired consciousness, increased pain sensation, lethargy...

CSF culture is to put the cerebrospinal fluid (or CSF) into a suitable environment with sufficient nutrients, then incubated at 37oC, CO2 (5%) to create conditions for bacteria (if necessary). yes) is developed. The types of culture media commonly used are agar plates or BHI liquid medium for bacterial growth.
After the incubation period as above 18-24 hours, if there are bacteria in the CSF, the bacteria will grow into colonies on the agar plate or make the BHI medium more turbid than before. Then, based on the morphological staining and bio-chemical properties of the bacteria, the bacteria were identified to the genus and the antibiotic susceptibility test was performed (by manual or automatic methods). .

Lumbar puncture is currently the safest and most common method for obtaining cerebrospinal fluid. The person performing the procedure must be a qualified physician who is well trained in the puncture procedure. Before performing the technique, the physician must explain the purpose and reassure the patient. Check vital signs, pulse, blood pressure,... stable.
Time of collection: By clinician to examine and make a decision How to get: This technique is performed by a specialist doctor by lumbar puncture. Container: Use an antifreeze-free tube, usually a sterile plastic tube or jar with a tight screw cap. Instruct the patient to lie down in the correct position, with both legs bent and knees close to the abdomen, both hands hugging the knees towards the chest. Determine the needle puncture area, disinfect with iodine and alcohol 70 degrees, then inject local anesthetic. Proceed to insert the needle into the spine and aspirate the cerebrospinal fluid out. During the procedure, attention should be paid to the patient's facial expression and condition. After collecting about 1 - 10ml of fluid, remove the needle, clean and cover the wound. At the end of the procedure, the patient is assigned to lie down for a short time. This helps prevent fluid leakage at the CSF puncture site

In addition to lumbar puncture, there are other methods of obtaining cerebrospinal fluid samples such as cisternal puncture, less common ventricular puncture.
After taking the cerebrospinal fluid specimen, it should be sent immediately to the laboratory. If it cannot be sent immediately, it can be stored at 35-37oC, if there is no incubator, it can be stored at room temperature but not more than 2 hours, absolutely do not store in the refrigerator.

At the laboratory:
Direct observation of cerebrospinal fluid: clear or cloudy, yellow or milky? Observation can guide the cause. Direct endoscopic staining from specimens: endoscopic staining after natural sedimentation, or after centrifugation. Gram stain to observe white blood cells, observe bacteria. The orientation of cocci, bacilli, gram-negative or gram-positive will help the clinician to use antibiotics when the results of antibiogram are not available. If TB is suspected, stain with Zielh Neelsen. Inform the clinician about the results of endoscopic staining. Culture: Use a sterile pipette to aspirate CSF and add 2-3 drops to blood agar, chocolate agar, UTI agar. Use sterile cultures to separate regions to create separate colonies. Bacterial proliferation is possible in BHI medium. Incubate blood agar and chocolate agar at 37oC, 5% CO2, incubate UTI agar at 37oC in normal atmosphere. After 24 hours, read the results: observe the colonies growing on the agar media and subculture from BHI, staining from the colonies. Then identify the bacteria and make an antibiogram. In case after 24h, bacteria do not grow, further incubate, and observe daily up to 72h. Returns negative if no growth. Vinmec International General Hospital is one of the hospitals that not only ensures professional quality with a team of leading doctors, modern equipment and technology, but also stands out for its examination and consulting services. and comprehensive, professional medical treatment; civilized, polite, safe and sterile medical examination and treatment space. Customers when choosing to perform tests here can be completely assured of the accuracy of test results.

Meningitis caused by many different causes: bacteria, viruses, parasites. Parasites can be examined directly from the specimen. Viral etiology is usually diagnosed by molecular biology methods. When bacterial meningitis is suspected, the doctor will order a culture of cerebrospinal fluid.
The bacterial causes of meningitis often vary with age. Common bacteria are Haemophilus influenzae, Meningococcal Neisseria meningitides, Streptococcus pneumoniae, E.coli or Staphylococcus aureus...