Most of the cases of meningitis are caused by viruses, and the disease usually proceeds in mild form. With a bacterial infection, the condition becomes potentially life-threatening especially in young children.
Frequent pathogens
Three types of bacteria as primary pathogens cause 75% of all cases of bacterial meningitis:
- Neisseria meningitidis, or meningococcus, is the most frequent pathogen that affects children, especially under the age of 5, and adolescents.
- Streptococcus pneumoniae - this bacterium is responsible for the development of pneumonia, and is also the cause of meningitis in children under two years old and in adults.
- Haemophilus influenzae - affects mainly children under 5 years, although it is now less common due to universal vaccination.
For the appointment of adequate therapy, it is necessary to determine the causative agent of the disease. In meningitis, examine cerebrospinal fluid (CSF) and blood. Samples obtained from the patient are sent for analysis to a microbiological laboratory.
Samples of CSF
CSF flushes the brain and spinal cord, and normally it is a colorless, transparent liquid. If suspected of having meningitis, a CSF sample is obtained by lumbar puncture, in which a sterile needle is inserted into the space around the spinal cord in the lower back. Smooth CSF strengthens the suspicion of bacterial meningitis. The sample is sent to the laboratory.
Blood Samples
In bacterial meningitis, the infection often enters the bloodstream with the development of septicemia, so the patient's blood is also directed to the microbiological examination. After the disinfection of the skin, blood is withdrawn from the vein. Blood is injected into a test tube with a nutrient solution for the cultivation of bacteria. Diagnosis of bacterial meningitis is based on the identification of pathogens in a CSF sample. It is necessary as soon as possible to obtain the result of the analysis for the timely appointment of adequate therapy. In a microbiological laboratory, specially trained personnel receive samples and immediately begin the study in order to provide the result to the doctor as soon as possible.
The CSF study
The tube with CSF is placed in a centrifuge - a high-speed rotating apparatus, whose contents are acted upon by centrifugal force. This leads to the fact that cells and bacteria accumulate at the bottom of the tube as a precipitate.
Microscopy
A sample of the sediment is examined under a microscope with counting the number of leukocytes. In bacterial meningitis, there is an increase in the number of these cells in the CSF. To detect bacteria on the slide, a special dye (Gram staining) is applied. If the sample contains pathogens from the three main pathogens, they can be detected by the characteristic staining of the bacteria. The result of microscopy and staining by Gram is immediately reported to the doctor so that he can prescribe the appropriate treatment.
Cultivation of the CSF
The remainder of the CSF is distributed over several Petri dishes with a culture medium for the cultivation of bacteria. CSF is normally sterile, so the detection of any bacteria is important. To separate these or other microbes, different nutrient media and cultivation conditions are required. Petri dishes are placed overnight in a thermostat and examined the next morning. Growing colonies of bacteria are stained by Gram. Sometimes resort to further cultivation of slowly growing microorganisms. A sample of blood received from the patient, the lab technician distributes in two test tubes for cultivation. In one of them, aerobic conditions of colony growth (in the presence of oxygen) will be maintained, in the other - anaerobic (in anoxic environment). After 24 hours of incubation, a small sample of material is removed from each tube and is cultured further under the same conditions as CSF. Any bacteria present will be identified, colored and identified. The result is immediately reported to the attending physician. In recent years, methods have been developed to detect the infection and identify the pathogen directly in the CSF or in the blood.
Fast Results
The latex agglutination test is based on the antigen-antibody reaction. Conducting this test is particularly useful if the patient has been given an antibiotic before the material is taken. Traditional methods give a result only in a day, whereas this modern test provides information much faster. This is of great importance in the rapid course of meningitis, which can end fatal.