Microbiological diagnosis of meningitis

"If the germ can be determined by the study of spinal fluid, specific antibiotic treatment should be instituted. If not, an empirical treatment begins that must be directed at the most frequent microbes according to the patient's characteristics".


Meningitis is the inflammation, usually of an infectious nature, of the meninges (membranes covering the brain and spinal cord).

The infection develops when there is an alteration of the humoral or cellular immunity or predisposing disorders, such as sinusitis, otitis media, lumbar puncture, brain catheters and trauma.

To make the diagnosis and to know which microorganism has caused the meningitis, it is necessary to collect a sample of cerebrospinal fluid (CSF) by lumbar puncture.

Although the test that confirms the presumptive diagnosis is the microbiolobic culture, after which an antibiogram (for bacteria) or antifungigram (for fungi) must be carried out, which will give us information on the degree of sensitivity of the microorganism to the various antibiotics or antifungals and thus put the most appropriate treatment in place.

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When is the microbiological diagnosis for meningitis made?

Depending on their cause, meningitis can be

  • Purulent or bacterial (produced by pyogenic bacteria).
  • Tuberculosis (produced by Mycobacterium tuberculosis).
  • Fungal (produced by fungi).
  • Viral (produced by viruses).
  • Amoebic (produced by free living amoebas).

Most frequent indications of this test:

  • Meningitis

Do you suspect you have this disease?

Microbiological diagnostic tests may be required

How is the microbiological diagnosis of meningitis made?

The cerebrospinal fluid (CSF) from a patient with suspected meningitis is the highest priority clinical specimen in a clinical microbiology laboratory and must be processed immediately in all cases.

The validity of the samples depends on the fulfillment of a series of norms related to the procedure of obtaining, the amount of sample obtained and the adequate transport.

The collection should be done with the maximum conditions of asepsis to avoid contamination of the sample and it should never come into contact with antiseptics or disinfectants.

Whenever possible, the CSF, like the rest of the clinical samples (haemocultures, otorhinopharyngeal or faeces samples, etc.), should be obtained before the establishment of the antibiotic treatment, although the diagnostic procedures should never delay its beginning.

The cerebrospinal fluid obtained is separated into three tubes to be analyzed individually, carrying out a cytological examination in one of the tubes, a biochemical examination in the other, and a Gram stain and microbiological culture in the third.

There are a series of rapid techniques (Gram staining, investigation of soluble antigens in the CSF, serum or urine and other stains, such as methylene blue, Indian ink or Ziehl-Neelsen stain) that give us an idea of the pathogenic agent causing meningitis.

Where do we do it?


The Infectious Diseases Service
of the Clínica Universidad de Navarra

This area works on the diagnosis and treatment of diseases produced by an infectious agent, which can be bacteria, virus, fungus and protozoa. Infections affect people by causing very different processes that can be located in any tissue of the human body, so it requires a specific approach.

This area carries out its activity on three fronts: care work, focused on the diagnosis and treatment of infectious diseases; teaching, with training of medical students, resident doctors and nurses; and research vocation, through the development of clinical and laboratory studies.

Organized in care units

  • Infections associated with biomaterials.
  • Nosocomial infections (multi-resistance).
  • Infections in immunosuppressed patients.
  • Community infection.
  • Traveler's medicine.
  • Prudent use and optimization program of anti-infective therapy.
  • Control of infection by multi-resistant microorganisms.
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Why at the Clinica?

  • We perform the traveler's assessment and analytical tests in less than 24 hours.
  • Second opinion consultation when the infection has not yet been resolved.
  • We ensure the prudent use of antibiotics.