Neisseria Meningitidis

Neisseria meningitidis, a gram negative cocci, is one of the three important bacteria causing meningitis. People with deficiencies of late acting complement components have an increased incidence of meningococcal bacteria.

Pathogenesis

Entry

• Transmission occurs by airborne droplets
• It colonizes the membranes of nasopharynx and upper respiratory tract

Spread

From the nasopharynx the organism enters into bloodstream and spreads to:

1. Meninges
2. Joints
3. Disseminate throughout the body causing meningococcemia

Virulence Factors

1. Polysaccharide capsule
2. Endotoxin –lipopolysaccharide (LPS)
3. IgA protease

a.      Polysaccharide Capsule

Enables the organism to resist phagocytosis by polymorphonuclear leukocytes.

b.      Lipopolysaccharide

Causes fever, shock, in purified form can reproduce many of the clinical manifestations of meningococcemia

c.       IgA protease

Helps bacteria to attach to the membranes of upper respiratory tract by cleaving secretory IgA.

Predisposing Factors

1. Late acting complement components (C6-C9) deficiencies
2. Closed/crowded environment
3. Malnutrition
4. Poor hygiene
5. Decreased neutrophils

Clinical Symptoms

1. Asymptomatic carriage
2. Acute meningitis
3. Meningococcemia
4. Waterhouse Friderichsen syndrome

Symptoms of Meningitis

1. Severe headache
2. Stiff neck
3. Dislike of bright light
4. Fever
5. Vomiting
6. Rash
7. Drowsiness

Laboratory Diagnosis

Specimen

1. CSF
2. Blood
3. Swabs from hemorrhagic skin lesions

Microscopy

Microscopy reveals:

1. Gram negative diplococcic
2. Kidney shaped
3. Non-motile
4. Non-spore forming
5. Fastidious organisms
6. With Leishman stain,  polymorphonuclear neutrophils are seen

Examination of CSF

On examination of CSF, it is seen that there is:

1. Decreased glucose
2. Increased lymphocytes
3. Increased proteins
4. Color is yellow

Culture

On chocolate agar, grey shiny colonies are observed, on incubation at 37ºC in 5% C0₂

Mueller Hinton agar may be used as well.

Biological Tests

1. Catalase positive
2. Oxidase positive
3. Ferments glucose
4. Ferments maltose
5. DNAase negative
6. Β-galactosidase negative
7. Glutamyl-aminopeptidase positive

Serological Tests

1. Latex agglutination test positive
2. Serum antibodies are not useful
3. PCR may be performed

Treatment

1. Benzyl penicillin
2. Chemoprophylaxis
3. Vaccination

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