Meningitis : Causative Agents and Lab diagnosis

Presentation on Etiological factors and Laboratory Diagnosis of Meningitis

Objective 1:

• To list the important causative agents of meningitis.

TYPES OF MENINGITIS

• Acute Pyogenic Meningitis
• Aseptic Meningitis
• Chronic Meningitis
  • Tuberculous
  • Fungal
  • Syphillitic
  • Protozoal
  • Helminthe

Causative agents of acute pyogenic meningitis

• Neonates
– Escherichia coli
– Group B streptococci
– Listeria monocytogenes
– Streptococcus pneumoniae

• Children
– Neisseria meningitidis
– Streptococcus pneumoniae,
– Haemophilus influenzae

• Adults
– Streptococcus pneumoniae,
– Neisseria meningitidis

• Elderly
– Listeria species

Causative Agents of Aseptic meningitis

• Common:
– Enteroviruses
– Herpes simplex virus 2 (HSV 2)
– Arthropod borne viruses (Tickborne, West Nile, Murray Valley, Japanese B)
– HIV (Human Immunodeficiency Virus)

• Less common
– Varicella zoster virus (VZV)
– Epstein Barr virus (EBV)

Causative Agents of Chronic Meningitis

Tuberculous meningitis

• Mycobacterium tuberculosis

Syphillitic meningits

• Treponema pallidum

Fungal meningitis

• Cryptococcus neoformans (most common in HIV patients)
• Candida albicans
• Mucor species
• Aspergillus fumigatus
• Coccidioides immitis
• Histoplasma capsulatum
• Blastomyces dermatitidis

Protozoal

• Toxoplasma gondii
• Trypanosoma
• Acanthamoeba

Helminthes

• Taenia solium

Objective 2:

• To outline laboratory diagnosis of bacterial meningitis.

Specimens

• CSF
• Blood
• Sample
• Nasal swab
• Peticheal lesions
• Autopsy

A. Examination of CSF

Macroscopy
• CSF is cloudy under increased pressure and blood may be seen.

CSF is centrifuged and following methods are used:

• Microscopy
• Culture

Microscopy

Unstained preparations: wet mounts

Stained smears:

• Common stains: Gram stain, Ziehl-Neelsen stain
• Fluorescent dyes: Acridine orange, Auramine rhodamine

Culture

Culture Media

• Enriched solid media- blood agar, chocolate agar
• Selective solid medium- MacConkey agar
• Robertson Cooked meat broth (for anaerobes)

Steps:

• CSF inoculated in culture media
• incubation at 35-36°C under 5-10% CO2
• Colonies appear after 18-24 hours, identified by morphology and biochemical reactions.

B. Blood culture

• incubated for 4-7 days, with daily subcultures

C. Nasopharyngeal Swab

• Useful for detection of carriers
• Done without contamination with saliva

D. Petechial lesions

Menigococci may be demonstrated by microscopy and culture

E. Autopsy

• Specimen from meninges, lateral ventricles, or surface of brain and spinal cord
• Within 12 hours of death of patient
• Smear or culture

Biochemical tests

• Catalase test
• Oxidase test
• Indole test
• Urease test
• Coagulase test
• Citrate Utilization test
• Triple sugar iron agar

Agglutination test:

• Direct slide agglutination test with specific antisera
• Latex agglutination test
• Immunoflourescence test
• Other rapid identification methods
• Molecular diagnosis – PCR test

Various changes in Acute Pyogenic Meningitis:

References:

• Textbook of Microbiology
• Diagnostic Microbiology

Prepared and Presented for Correlation Seminar in Kist Medical College by:

Sharmila Phelu (76) Shradda Shrestha (77) Shuvechha Pandey (78) Srijana Shakya (79) Sulav Shrestha (80) Surakshya Rayamajhi (81) Surendra Pariyar (82) Sushil Dulal (83) Sushmita Sharma (84) Tulsi Ram Shrestha (85) Uday Chandra Prakash (86) Ujjwol Giri (87) Ujwol Karmacharya (88)