Chapter 8: Gram-negative Bacteria: Neisseria Flashcards
Neisseria - morphology?
cocci in pairs (diplococci)
each coccus is shaped like a kidney bean, and the concave sides face each other, so the diplococcus looks like a small donut
Neisseria - Gram-stain?
Gram-negative
What are the two families of Gram-negative diplococci?
Neisseria
Moraxella (in the greater family of Neisseriaceae)
Which 2 species of Neisseria cause disease in humans?
Neisseria meningitidis
N. gonorrhoeae
Gram-negative kidney-shaped diplococci?
Neisseria
Neisseria meningitidis - Gram stain?
Gram-negative
Neisseria meningitidis - morphology?
kidney bean shaped diplococci with concave sides facing each other, forming the appearance of a donut
Neisseria meningitidis - metabolism?
facultative anaerobe (or aerobic)
What bacteria is aka meningococcus?
Neisseria meningitidis
Neisseria meningitidis - encapsulated?
polysaccharide capsule
What virulence factors does Neisseria meningitidis exhibit? (5)
1) polysaccharide capsule - 13 serotypes
2) endotoxin (LPS)
3) IgA1 protease
4) have unique proteins that can extract iron from transferrin, lactoferrin, and hemoglobin
5) Pili: adherence
What is the purpose of Neisseria meningitidis polysaccharide capsule?
antiphagocytic (as long as the human host doesn’t have specific antibodies to opsonize the bacterium)
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the blood?
hemorrhage (blood vessel destruction) and sepsis
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the skin?
petechiae (petechial ash): tiny round red dots of hemorrhage on the skin
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the internal organs when disease progresses? What is this syndrome called?
hemorrhage of adrenal glands (Waterhouse-Friderichsen syndrome)
What is the purpose of Neisseria meningitidis pili?
allow attachment to human nasopharyngeal cell, and undergo antigenic variation to avoid attack by the immune system
Does everyone with Neisseria meningitidis nasopharyngeal infection become symptomatic?
No, 5% are asymptomatic (carriers) and develop anti-meningococcal antibodies
What groups are at high risk of becoming infected with Neisseria meningitidis? (3)
1) infants aged 6 months to 2 years
2) army recruits
3) college freshmen
How is Neisseria meningitidis transmitted?
via respiratory droplets
How do patients with invasive Neisseria meningitidis infection present? (3)
1) bacterial meningitis: stiff neck, headache, fever, chills
2) petechial rash: tiny round red dots of hemorrhage in the skin due to release of endotoxin (vascular necrosis and inflammation)
(3) sepsis
Which bacteria are responsible for most neonatal meningitis (<3mos)?
1) Group B streptococcus
2) Listeria monocytogenes
3) E. coli
Which bacteria are responsible for meningitis in older children (after maternal antibodies passively given to fetus wane and before new antibodies develop)?
1) Haemophilus influenzae
2) Neisseria meningitidis
What causes the petechiae observed with Neisseria meningitidis infection?
release of LPS endotoxin from the meningococcus, causing vascular necrosis, and inflammatory reaction, and hemorrhage into the surrounding skin
What is Waterhouse-Friderichsen syndrome?
Fulminant meningococcemia (N. meningitidis septic shock) - bilateral hemorrhage into the adrenal glands occurs, causing renal insufficiency. Abrupt onset of hypotension and tachycardia, along with rapidly enlarging petechial skin lesions. DIC and coma may develop. Death can occur rapidly (6-8 hours).