Neisseria

Question 0

Meningococcus pathogenesis

Answer 0

Airborne droplet (crowded conditions) -> nasopharynx (5% carriers) -> multiplies outside cells
Endotoxin -> small vessels
Capsule - antiphagocytic
 - serogroups (A, B, C, Y, W-135) -> serotypes per outer membrane proteins
 - most adults have antibodies, disease from new serotype exposure

Rare: progress to bloodstream (days to week)
- adrenal damage -> shock = Waterhouse-Frederichson syndrome

Question 1

Overview of Neisseria

Answer 1

N meningititis aka meningococcus
N gonorrhoeae aka gonococcus

Gram (-) diplococci
Growth - Thayer-Martin = selective at 5-10% CO2
- chocolate agar + vanco (vs Gram +), colistin (vs enterics), nystatin (vs fungal) - non-path Neisseria also won’t grow
Oxidase positive (all Neiss) - dye -> pink -> black
Fermentation
- gonorrhoeae - glucose +, malt, lact, suc (-)
- meningitidis - glu and malt +, lact, suc (-)
- non-path - glu, malt, lact +, suc (-)
Killed by drying, disinfection, etc
No animal reservoir

Virulence:

• protease vs IgA1
• pili, OMP’s -> adherence
• LOS - endotoxin, like LPS but no O side chains

Question 2

Meningococcus epidemiology

Answer 2

Sub-Saharan meningitis belt - Ethiopia - Senegal
- dry winter - wind, cold, URI -> predisposed
- overcrowding, large population movements
- Type A
Vaccination - quadrivalent, conjugate - moderately successful
- A, C, Y, W-135 covered, B = sialic acid - not recognized by C3b
- MenAfriVac - specifically for Africa -> mass campaigns

Question 3

Meningococcus clinical

Answer 3

Presentation: URI -> fever, stiff neck, petechiae -> ecchymosis
Blood, nasal, CSF -> look for Gram (-) diplococci
- also latex agglutination, fermentation

Tx: immediate!

• IV penicillin or 3rd generation cephalo (ceftriaxone)
• prophylaxis for contacts = rifampin (secreted) or ciprofloxacin

Question 4

Meningitis

Answer 4

High clinical suspicion -> CSF testing

Fever in neonates - Group B Strep, E coli K1
Neuro + petechiae -> N meningititis
Children -> H influenzae, Strep pneumoniae - hard to dx

Question 5

Gonococcus presentation

Answer 5

STI - direct contact -> GU, rectal, pharyngeal

• > pili anchor (hours) -> intracellular -> connective tissue
• > yellow pus, inflammation (2-3 d males, variable females)

-> epididymis, prostate (fairly rare)
-> Fallopian -> PID
-> arthritis-dermatitis (occurs without GU sx)
Asymptomatic - frequent females, 1-10% males

Question 6

Gonococcus overview

Answer 6

Gram (-) diplococcus
- visualize in pus, inside phagocytes or epithelial
Serotypes (100) = pilus - adhesion, antiphagocytic
- no capsule, no endotoxin
Worldwide pandemic, frequently asymptomatic
- assume co-infection with Chlamydia trachomatis

Question 7

Opthalmia neonatorum

Answer 7

Birth canal -> conjunctiva -> blindness (half of blindness!)
Prophylactic tx legally required

Tetracycline
Erythromycin
1% silver nitrate

Question 8

Gonococcus dx and tx

Answer 8

Dx - history + pus
- Gram (-) diplococci in pus, inside phagocytes
- culture before tx, oxidase negative
Tx: lots of resistance!
- plasmid penicillinase (PenR) = PPNG
- tetracycline resistance (TetR) = TRNG - can mobilize PenR
- chromosome-mediated resistance = CMRNG - moderate permeability vs penicillin, tetracycline, cephalosporins
- current regimen = IM ceftriaxone + tetra, doxy or azithro for Chlamydia
Immunity - weak, many serotypes, no vaccine -> repeated infections