Neisseria meningitides

Categorization
Cell Wall: Gram Negative Shape: Cocci, Diplococci
Metabolism: Obligate Aerobe
Culture and Detection
  • Culture: All Neisseria can be selectively grown on the Thayer-Martin chocolate agar selective media supplemented with the antibiotics Vancomycin, Colistin, and Amphotericin
  • Detection: Detection of intracellular gram negative diplococci
  • Biochemistry: G. meningitides is positive for Maltose fermentation which can distinguish it from G. gonorrhea
Virulence Factors
  • Capsule: Meningococcus possseses an antiphagocytic polysaccharide capsule. Multiple serotypes do exist; however, antibodies to the capsule are protective.
  • IgA Protease: Reduces mucosal immunity
  • Outermembrane Blebs: Meningococcus sheds blebs of its bacterial outer membrane (See: Bacterial Cell Wall) which contains the highly inflammatory lipopolysaccharide. It is thought that the rapid inflammatory response to Meningococcal infection may be due to systemic shedding of these outermembrane blebs.
Clinical Consequences
  • Overview
    • Meningococcus is part of the nasopharyngeal flora in a small fraction of the population and causes no symptoms. In some individuals, bacteria spread systemically and can cause the following complications.
  • Meningococcemia
    • Meningococcemia refers to a sepsis caused by meningococcus and is characterized by a unique purpuric and petechial skin rash along with high fevers.
  • Waterhouse-Friderichsen Syndrome
    • When Meningococcemia becomes fulminant it is characterized by septic shock and DIC. Frequently there is acute hemorrhage into the adrenal cortex resulting in acute adrenocortical insufficiency.
  • Meningitis
    • Meningitis is the most common manifestation of pathological infection and often occurs in the absence of clinical meningococcemia.
Immunity and Incidence
  • Immunity
  • Incidence
    • Infections occur both sporadically and in epidemic waves. Epidemics occurs in those living in close quarters such as college dormitories or army barracks. Infants tend to be infected during the antibody window between 6mo - 2 yrs.
Vaccination
  • Vaccine of purified capsular polysaccharides exist for prominent serotypes.
Treatment
  • Penicillin G or Ceftriaxone