Medical Analysis

Comprehensive Medical Analysis of Cerebrospinal Fluid Examination Part – 5: Advanced Microbiological Investigations and Differential Diagnosis in Meningitis

Introduction to Cerebrospinal Fluid Examination and Microbiological Investigations

Cerebrospinal Fluid Examination represents an extensive and clinically significant diagnostic topic [11, 12]. Proper understanding is crucial because findings profoundly influence both diagnosis and prognosis, directly impacting patient care and clinical decision-making [11, 12]. Due to the vastness of this subject, covering every aspect within a single presentation is not feasible [11, 12]. This presentation constitutes part five of a series of six on Cerebrospinal Fluid Examination [11, 12], and viewers are encouraged to review the remaining presentations for a complete and comprehensive understanding [11, 12]. Microbiological investigations cover bacterial meningitis, amoebic meningitis, viral meningitis, and fungal meningitis [1, 2, 8, 9, 10].

Bacterial Meningitis Pathogens and Diagnostic Modalities

Bacterial meningitis involves specific causative agents dependent on patient age and clinical risk factors [1, 2, 4]. Neonates are commonly affected by group B streptococcus [1, 2, 4]; newborns up to one month by E. coli and other gram-negative bacilli [1, 2, 4]; patients three months and above by Neisseria meningitidis and Haemophilus influenzae [1, 2, 4]; neonates, elderly, alcoholics, and immunosuppressed individuals by Listeria monocytogenes [1, 2, 4]; and patients with cerebrospinal fluid shunts, head injuries, or neurosurgery by Staphylococcus, aerobic gram-negative bacilli, and Propionibacterium [1, 2, 4].

Diagnostic methods for bacterial meningitis include Gram stain, where all specimens should be concentrated by centrifuge [2, 11]. Acridine orange stain offers higher sensitivity when polymorphonuclear leucocytes are present but no organisms are detected [11]. Culture remains the mainstay for diagnosis [1, 2]. Additional rapid diagnostic assays include Binax NOW, a lateral flow immunoassay intended for qualitative detection of nucleocapsid protein antigen from SARS-CoV-2, and Strep pneumoniae antigen tests using immunochromatographic membrane assay to detect C-polysaccharide cell wall antigens common to all serotypes of Staphylococcus pneumoniae [2, 5]. Latex agglutination bacterial antigen test finds best application in partially treated community-acquired meningitis [1, 2]. Limulus lysate assay detects endotoxins in newborns [5]. Polymerase chain reaction involves sequencing of 16s ribosomal RNA in cerebrospinal fluid [5]. Nucleic acid amplification tests are utilized for patients on antimicrobial therapy or for detecting more fastidious organisms like Neisseria meningitidis [1, 2].

Tuberculous and Spirochetal Meningitis Diagnostics

Tuberculous meningitis presents with elevated protein and lymphocytes [6]. Diagnostic methods include PCR nucleic acid amplification, which is rapid and accurate [6]. A negative PCR result does not exclude the diagnosis; if clinical suspicion remains high, empiric therapy is initiated [6]. IDOT ELISA serves as a standard method to detect antigens and antibodies [6]. Ligase chain reaction amplification provides rapid early diagnosis [6]. Adenosine deaminase levels greater than 15 U/L support the diagnosis [6]. Spirochetal meningitis is primarily seen in human immunodeficiency virus infection [7, 12]. Methods of detection include VDRL, which exhibits high specificity and 50 percent to 60 percent sensitivity, where a positive cerebrospinal fluid VDRL test points toward neurosyphilis [7]. Fluorescent treponemal antibody absorption is sensitive and specific, though its role in neurosyphilis remains controversial [7]. A non-reactive serum fluorescent treponemal antibody absorption rules out neurosyphilis, while a reactive serum but non-reactive cerebrospinal fluid test also rules out neurosyphilis [7]. A reactive fluorescent treponemal antibody absorption indicates active, asymptomatic, or treated neurosyphilis [7].

Viral, Amoebic, and Fungal Meningitis Overview

Viral meningitis is caused by echovirus, poliovirus, and coxsackievirus [11]. These cases occur rarely and typically require no specific treatment, though antiviral treatment is administered in rare cases [11]. Primary amoebic meningoencephalitis is caused by free-living amoebae, Naegleria fowleri or Acanthamoeba species [8]. Features of meningitis due to Naegleria include neutrophilic pleocytosis, decreased glucose levels, elevated proteins, and the presence of red blood cells [8]. Features of meningitis due to Acanthamoeba manifest as granulomatous meningitis [8]. Methods of detection for primary amoebic meningoencephalitis include visualizing Naegleria trophozoites by light microscope using a wet mount, staining intact organisms by Giemsa while distinguishing them from macrophages, and using acridine orange stain to differentiate amoebae appearing bright red from leucocytes appearing bright green [8]. Fungal meningitis involves Cryptococcus neoformans as the most common organism, alongside Candida [9, 10]. Features of fungal meningitis include lymphocytic pleocytosis, decreased glucose levels, and elevated proteins [9, 10]. Methods of detection for Candida involve routine aerobic culture [10], while detection for Cryptococcus utilizes the cryptococcus antigen test and India ink preparation [9].

Comparative Lumbar Cerebrospinal Fluid Findings in Meningitis

For Non-Medicos

What Is Cerebrospinal Fluid Microbiology Testing?

Cerebrospinal fluid microbiology testing identifies harmful germs, including bacteria, viruses, fungi, and parasites, that cause dangerous brain and spinal cord infections like meningitis [1, 2, 8, 9, 10, 11].

How Doctors Diagnose Different Types of Meningitis

Medical professionals analyze fluid pressure, white blood cells, protein levels, and sugar content, alongside specialized staining and culture tests, to pinpoint whether an infection is bacterial, viral, fungal, or tubercular [1, 2, 6, 8, 9, 10, 11].

References:

1. van de Beek D, de Gans J, Tunkel AR, Wijdicks EF. Community-acquired bacterial meningitis in adults. N Engl J Med. 2006;354(1):44-53.

2. Tunkel AR, Hartman BJ, Kaplan SL, Kaufman BA, Roos KL, Scheld WM, Whitley RJ. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004;39(9):1267-1284.

3. Hasbun R, Abrahams J, Jekel J, Quagliarello VJ. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001;345(24):1727-1733.

4. Thigpen MC, Whitney CG, Messonnier NE, Zell ER, Lynd LD, Zhou F, et al. Bacterial meningitis in the United States, 1998-2007. N Engl J Med. 2011;364(21):2016-2025.

5. Brouwer MC, Thomsen MK, Williamson JC, van de Beek D. Cytokines and chemokines in cerebrospinal fluid in human bacterial meningitis: a systematic review. Crit Care Med. 2013;41(1):239-248.

6. Thwaites GE, Chau TT, Mai NT, Drobniewski F, McAdam K, Farrar JJ. Tuberculous meningitis. J Neurol Neurosurg Psychiatry. 2000;68(3):289-299.

7. Marra CM, Maxwell CL, Smith SL, Lukehart SA, Rompalo AM, Eaton M, et al. Cerebrospinal fluid abnormalities in patients with syphilis: association with clinical and laboratory features. J Infect Dis. 2004;189(3):369-376.

8. Centiles MA, Wright RL. Naegleria fowleri: meningoencephalitis. Clinical, pathological, and epidemiological features. Medicine (Baltimore). 1991;70(3):147-160.

9. Perfect JR, Dismukes WE, Dromer F, Goldman DL, Graybill JR, Hamill RJ, et al. Clinical practice guidelines for the management of cryptococcal disease: 2010 update by the Infectious Diseases Society of America. Clin Infect Dis. 2010;50(3):291-322.

10. Baddour LM, Pappas PG, Apisarnthanarak A, Alexander BD, Kauffman CA, Kusne S, et al. Update on the management of candidiasis: 2016 guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2016;62(4):e1-e50.

11. Seehusen DA, Reeves MM, Fomin DA. Cerebrospinal fluid analysis. Am Fam Physician. 2003;68(6):1103-1108.

12. Wiley CA, Achim CL. Human immunodeficiency virus encephalitis and the central nervous system. Ann Neurol. 1994;36(Suppl):S18-S26.

13. Bodilsen J, Dalager-Pedersen M, van de Beek D, Brouwer MC, Nielsen H. Dexamethasone and mortality in bacterial meningitis: a nationwide population-based cohort study. J Infection. 2018;77(6):500-505.

14. Prasad K, Singh A, Ryan H. Corticosteroids for managing tuberculous meningitis. Cochrane Database Syst Rev. 2016;4(4):CD002244.

15. Swartz MN. Bacterial meningitis: a review of selected aspects. N Engl J Med. 1984;311(14):912-919.

FAQ’s:

• What is cerebrospinal fluid microbiology testing?
  Testing identifies bacteria, viruses, fungi, and parasites causing dangerous infections like meningitis.

• What agents cause bacterial meningitis?
  Causative agents include group B streptococcus, E. coli, Neisseria meningitidis, and Listeria monocytogenes.

• What stains detect bacterial pathogens?
  Gram stain and acridine orange stain are used to identify bacterial organisms in specimens.

• How is tuberculous meningitis diagnosed?
  Diagnosis involves PCR nucleic acid amplification, IDOT ELISA, and adenosine deaminase levels.

• How is spirochetal meningitis detected?
  Detection utilizes VDRL and fluorescent treponemal antibody absorption tests, primarily seen in HIV.

• What viruses cause viral meningitis?
  Echovirus, poliovirus, and coxsackievirus are the causative agents of viral meningitis.

• What amoebae cause meningoencephalitis?
  Primary amoebic meningoencephalitis is caused by free-living Naegleria fowleri or Acanthamoeba species.

• What organism causes fungal meningitis?
  Cryptococcus neoformans and Candida species are the primary organisms responsible for fungal meningitis.

• How is Cryptococcus detected?
  Detection methods utilize the cryptococcus antigen test and India ink preparation of cerebrospinal fluid.

What do bacterial findings show?
Bacterial meningitis shows increased opening pressure, high leukocyte counts, low glucose, and high proteins.

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