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Infectious Diseases > Haemophilus, Bordetella, Legionella > Flashcards

Haemophilus, Bordetella, Legionella Flashcards

1
Q

Haemophilus influenzae reservoir?

A

-Man only (obligate human parasite)

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2
Q

Haemophilus influenzae transmission?

A

Respiratory

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3
Q

Haemophilus influenzae virulence?

A
  1. Capsule (6 types a-f; b most virulent)
  2. Attachmet pili
  3. IgA protease
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4
Q

Haemophilus influenzae toxins?

A

No exotoxins produced

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5
Q

Clinical presentation of encapsulated Haemophilus influenzae?

A

Usually HIb (type B capsule)

  1. Meningitis
  2. Acute epiglottitis
  3. Septic arthritis (infants)
  4. Sepsis
  5. Pneumonia
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6
Q

In whom does Haemophilus influenzae B cause meningitis?

A

Primary cause of meningitis in infants 3-36 months.

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7
Q

Complications of HIb meningitis?

A
  • mental retardation
  • seizures
  • deafness
  • death
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8
Q

Which patients are suscpetible to HIb sepsis?

A

Patients without spleens

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9
Q

Clinical presentation of non-encapsulated H. Influenzae?

A
    1. otitis media
    1. Sinusitis
    1. COPD exacerbation and pneumonia
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10
Q

Treatment of Haemophilus influenzae infection?

A

Second or third gen cephalosporin (can acquire ampicillin resistance via plasmids)

  • cefotaxime
  • ceftriaxone
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11
Q

How does HIb acquire ampicillin resistance?

A

Via plasmids

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12
Q

What is used in the HIb vaccine?

A

H. influenzae polysaccharide capsule of type B strain conjugated to diptheria toxoid; given in a combination vaccine with DTPa (diphtheria-tetanus-whooping cough), polio and hepatitis B

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13
Q

When is HIb vaccine given?

A

2, 4, 6 months

Booster at 12 months

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14
Q

What does H. influenzae require for growth?

A
  • X factor: Haematin (for cytochrome system)

- V factor: NAD+ (for metabolic activity)

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15
Q

Why does non-encapsulated H. influenzae cause only local infection?

A

lacks virulent invasiveness of capsulated HI

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16
Q

Which bacteria are responsible for meningitis within the first 3 months of age?

A
  1. Listeria monocytogenes
  2. E. Coli
  3. Group B strep
17
Q

Which bacteria are responsible for meningitis post 3 months of life?

A

after maternal antibodies passively given to foetus wane:

  1. Neisseria meningitides
  2. HIb
18
Q

Gram stain of H. influenzae joint aspirate in septic arthritis?

A

Pleomorphic G-ve rods

19
Q

What is haemophilus ducreyi?

20
Q

Toxins produced by haemophilus ducreyi?

A

No toxins produced

21
Q

Clinical presentation of haemophilus ducreyi?

A

Chancroid: painful genital ulcer

-often a/w unilateral genital LNs: can rupture releasing pus

22
Q

Treatments for H. ducreyi?

A
  1. Azithromycin
  2. Ceftriaxone
  3. Ciprofloxacin
23
Q

Diagnosis of H. ducreyi?

A

Gram stain and culture of ulcer exudate +/- pus released from swollen LN

24
Q

Bordatella pertussis reservoir?

25
Q

how is bordatella pertussis spread?

A

Respiratory route

26
Q

Bordatella pertussis virulence factors?

A
  1. Capsule
  2. beta lactamase
  3. filamentous haemagluttinin (FHA): pili from surface enabling binding to ciliated epithelial cells of bronchi
27
Q

Bordetella pertussis toxins?

A
  1. Pertussis toxin
  2. Extracytoplasmic adenylate cyclase
  3. Filamentous haemagluttinin
  4. Tracheal cytotoxin
28
Q

What are the actions of the pertussis toxin?

A

Activates G proteins which inc cAMP, resulting in:

  1. Inc sensitivity to histamine
  2. Increased insulin release
  3. increased number of lymphocytes in blood
29
Q

What is the action Extracytoplasmic adenylate cyclase produced by Bordetella pertussis?

A

Weakens neutrophils, lymphocytes and monocytes

30
Q

What is the clinical presentation of Bordetella pertussis?

A

Whooping cough. 3 stages:

  1. Catarrhal phase: pt highly contagious (1-2w). Low grade fever, runny nose, mild cough.
  2. Paroxysmal phase (2-10w): whooping cough. ABx ineffective
  3. Convalescent phase
31
Q

Treatment Whooping Cough?

A

-Erythromycin (only if given before paroxysmal phase)

32
Q

Reservoir legionella pneumophila?

A

Ubiquitous in man and natural water environments. Common:

  • air conditioning systems
  • cooling towers
33
Q

Virulence legionella pneumophila?

A
  1. Facultative intracellular parasite: type IV secretion system inhibits macrophage phagosome / lysosome fusions
  2. Cu-Zn superoxide dismutase and catalase-peroxidase protects bacteria from macrophage oxidative burst
  3. pili and flagella promote attachment and invasion
  4. Secretion of protein toxins (RNAse, phospholipase A / C)
34
Q

Clinical presentation legionella pneumophila?

A
  1. Pontiac fever: HA, fever, muscle aches, fatigue. Self -limiting (usu 1w)
  2. Legionnaires’ Disease: pneumonia- fever and non-productive cough
35
Q

Treatment legionella pneumophila?

A
  1. Erythromycin

2. Rifampin

Infectious Diseases (10 decks)

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