Gram Negative Cocci

Question 1

Neisseria meningitidis

Clinical case: Early one evening, a young soldier in an army base enters the emergency room with a petechial rash, fever, and headache. Physical exam reveals a positive Kernig’s sign, nuchal rigidity, and impaired mental status. An LP is performed showing increased PMNs, increased protein, decreased glucose as well as intracellular kidney bean-shaped diplococci.

Answer 1

Structure: encapsulated, diplococcus, six serotypes (A, B, C, X, Y, W 135)
Reservoir: human nasopharynx (not normal flora)
Transmission: inhalation
Toxin/Pathogenesis: bacteria evades IgA antibodies with IgA protease –> crosses mucosa via phagocytic vacuoles –> enters and multiples in the bloodstream –> endotoxin is released (Lipooligosaccharide, LOS) –> vascular necrosis and hemorrhage in the skin
Disease: meningococcemia with petechial rash; meningitis (2-18 years) –> fever, stiff neck, photophobia; infulminant cases –> vascular necrosis and hemorrhage in adrenal glands –> adrenal insufficiency (Waterhouse-Friedrichsen syndrome) –> shock, DIC –> multiorgan failure –> possible death
At risk: complement deficient,