Gram Negative: Neisseria

Question 1

General features of Neisseria

Answer 1

• Neisseria is the ONLY pathogenic Gram negative cocci!

- it is a diplococcus

Question 2

What are the major species of Neisseria? What does each cause?

Answer 2

• Neisseria meningitidis: meningitis and severe sepsis
• Neisseria gonorrhoeae: gonorrhea (urethritis, pelvic inflammatory disease), bacteremia, septic arthritis, ophthalmia neonatorum
• Moraxella catarrhalis: otitis media, COPD exacerbations, pneumonia
• Kingella kingae: endocarditis, septic arthritis, osteomyelitis
• (Moraxella and Kingella are in the same family as Neisseria)

Question 3

What are the major virulence factors of Neisseria meningitidis? Which groups are at the greatest risk? How do we treat it?

Answer 3

• (causes meningitis and severe sepsis)
• virulence factors: anti-phagocytic capsule (serotypes A, B, and C are pathogenic), LPS endotoxin (b/c Gram neg), IgA1 protease, pili (attaches to nasopharynx)
• at risk: infants (6 mo - 2 yrs), army recruits, college freshmen
• treat with pencillin G or ceftriaxone

Question 4

Explain the pathogenesis of disease induced by Neisseria meningitidis.

Answer 4

• attaches to nasopharynx and spreads via respiratory secretions
• can then invade into the bloodstream to cause meningococcal disease (note that this pathogenic invasion step is actually quite rare)
• multiplication in blood results in meningococcemia; patients will develop abrupt fever, chills, petechiae, and arthralgia
• meningococcemia can progress into meningitis and less commonly into a fulminant meningococcemia (severe septic shock)

Question 5

Why is fulminant meningococcemia so deadly? What is it also known as?

Answer 5

• (this is a very severe form of meningococcal disease)
• this is septic shock due to the bilateral hemorrhage of the adrenal glands, leading to adrenal insufficiency, which results in hypotension, shock, DIC, coma, and death
• this is AKA Waterhouse-Friderichsen syndrome!

Question 6

Which organisms are the main causes of meningitis in infants (not neonates)?

Answer 6

• Neisseria meningitidis and Haemophilus influenzae type b
• this is because of the antibody window period that exists between 6 months and 2 years of age (after the maternal passive breast-milk antibodies wear off and before the child creates his own)
• (neonatal meningitis is due to Listeria monocytogenes, group B strep/Streptococci agalactiae, and Escherichia coli)

Question 7

How do we culture Neisseria meningitidis?

Answer 7

• with a Thayer-Martin VCN media
• this is chocolate agar (heated blood agar; blood agar turns brown when heated) with vancomycin (kills Gram pos), colistin/polymyxin (kills all Gram neg except for Neisseria), and nystatin (kills fungi)

Question 8

What are the major virulence factors of Neisseria gonorrhoeae? How do we treat it?

Answer 8

• (causes gonorrhea)
• virulence factors: LPS endotoxin, pili (adhesion, highly variable for Ab evasion), porin and Opa proteins (promote invasion)
• treat with ceftriaxone (many strains are penicillin resistant) and add doxycycline for Chlamydia (co-infection of these two organisms is very common)

Question 9

How does gonorrhea present in men? What about women? neonates?

Answer 9

• both: urethritis, septic arthritis, gonococcal bacteremia (rare)
• men: rectal gonococcal infection
• women: cervix infection and progression to pelvic inflammatory disease (PID)
• neonates: ophthalmia neonatorum (this is an eye infection on the 1st or 2nd day of life; also due to Chlamydia; all neonates are given prophylactic erythromycin eye drops)

Question 10

What is pelvic inflammatory disease? Which organisms can cause it? What are some major complications?

Answer 10

• PID is endometritis (uterus inflammation), salpingitis (fallopian tubes), and/or oophoritis (ovaries); plus fever, abdominal pain, and cervical tenderness
• caused by Neisseria gonorrhoeae and Chlamydia trachomatis
• complications: sterility (fallopian tube scarring), increased risk of ectopic pregnancy (fallopian tube scarring), abscess formation, peritonitis, and peri-hepatitis (infection of the liver capsule, AKA Fitz-Hugh-Curtis syndrome)

Question 11

What diseases does Moraxella catarrhalis cause?

Answer 11

• otitis media in children
• COPD exacerbations
• pneumonia in elderly

Question 12

Which organisms are the major causes of otitis media in children?

Answer 12

• Streptococcus pneuomoniae (30%)
• Haemophilus influenzae (25%)
• Moraxella catarrhalis (15-20%)

Question 13

What diseases does Kingella kingae cause?

Answer 13

• septic arthritis, osteomyelitis, endocarditis of native and prosthetic valves
• it is a HACEK organism

Question 14

What is a HACEK organism?

Answer 14

• this is a grouping of slow-growing bacteria that can cause endocarditis of both native and prosthetic valves
• HACEK: Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella