Infectious Disease Online
Pathology of Meningococcal Infection
Neisseria meningitides are
Gram negative, diplococci with capsule.
In addition to antiphagocytic factor in capsule, bacteria produce powerful endotoxin, which are responsible for disease.
Transmission of infection is from healthy carrier or recently recovered patients, by airborne droplets, particularly in crowded environment.
2-5% healthy persons harbour menigococci in their nasopharynx.
The disease is not highly contagious and infection rate, rarely exceeds 1 in 1000, even during epidemic.
Infection may be Sporadic, Endemic or Epidemic:
Meningococci causes two distinct, fatal diseases:
1. Meningococcal meningitis ;
2. Fulminant meningococcemia.
1. Meningococcal meningitis:
The disease may be described under three stages:
at the site of entry i.e. nasopharynx.
Characterized by septicemia.
Occasionally, there may be massive purpuric hemorrhage & involved area becomes gangrenous.
Stage-III: Localization, mainly in the meninges.
This is associated with headache, vomiting & stiff-neck, followed by delirium & coma.
Due to blood-brain barrier bacteria cannot enter to brain tissue.
It causes acute inflammation of the leptomeninges (Pia and arachnoid matter).
Meningeal vessels are congested with exudates in the subarachnoid space and minute areas of hemorrhage.
In advanced stage thick purulent exudates is seen, mainly in the base of the brain.
Inflammation and degenerative changes are present in the superficial layer of brain due to diffusion of toxin.
In chronic form, internal hydrocephalus may develop.
2. Fulminant Meningococcemia:
- Sudden onset of fever, tachycardia & hypotension are the early symptoms.
- Sudden toxemia kills the patient within 6-26 hours.
- Evidence of meningitis is uncommon due to rapid course.
- Meningococcemia is the main cause of Waterhouse-Friderichsen Syndrome in children, which is characterized by:
(i) Purpura (ii) Circulatory collapse and (iii) Adrenal hemorrhage.
- Patients surviving early phase of meningococcemia develop allergic manifestations:
(i) Polyarthritis (ii) Cutaneous vasculitis leading to ulceration. (iii) Gangrene of distal portion of limbs.
Cutaneous Lesions :
The cutaneous lesions in meningococcal septicemia show an acute vasculitis with fibrin thrombi in the small blood vessels of the dermis and extravasation of fibrin.
There are neutrophils in and around the vessels.
Leukocytoclasis is not a conspicuous feature.
In pustular lesions of chronic meningococcemia there are intraepidermal and subepidermal collections of neutrophils.
Vasculitis is present in the dermis. The infiltrate contains some lymphocytes in addition to neutrophils.
-Diagnostic Microbiology -Fourth Edition. JB Lippincott Company,1992, pp.370-398
-Meningococcal Disease-Journal of Medical Microbiology.1993;39(1):3-25.
-Infectious Diseases -Fourth Edition. Churchill Livingstone, 1995, p1896-1906
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