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Microbiology > Haemophilus, Bordetella, And Legionella > Flashcards

Haemophilus, Bordetella, And Legionella Flashcards

0
Q

How is H.influenza transmitted?

A

Via respiratory route.

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1
Q

Where is H.influenza found?

A

Humans only.

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2
Q

What is the virulence of H.influenza?

A
  1. Capsule: 6 types a-f.
  2. Attachment pili
  3. IgA1 protease
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3
Q

What is the most virulent capsule type of H.influenza?

A

b

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4
Q

What are the toxins of H.influenza?

A
  1. Cytolethal distending toxin (CDT)

2. Hemolysin

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5
Q

What can encapsulated H.influenza (usually type B) cause?

A
  1. Meningitis (3-36 months).
  2. Acute epiglottitis
  3. Septic arthritis in infants
  4. Sepsis (asplenic patients)
  5. Pneumonia
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6
Q

What can nonencapsulated H.influenza cause?

A
  1. Otitis media
  2. Sinusitis
  3. COPD exacerbation and pneumonia
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7
Q

How can we identify H.influenza?

A
  1. Gram stain
  2. Chocolate agar - high CO2 environment at 37C.
  3. ELISA - Latex particle agglutination
  4. Positive Quellung reaction due to its capsule (like S.pneumoniae).
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8
Q

What is important to keep in mind about H.influenza?

A

It requires two factors for growth (both found in blood).

  • X factor: hematin
  • V factor: NAD+
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9
Q

How is Haemophilus ducreyi transmitted?

A

Sexually

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10
Q

What are the toxins of H.ducreyi?

A

No exotoxins

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11
Q

What can H.ducreyi cause?

A

Chancroid

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12
Q

What is a chancroid?

A

Painful genital ulcer, often associated with unilateral swollen lymph nodes that can rupture, releasing pus.

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13
Q

How can we identify H.ducreyi?

A

Gram stain and culture of ulcer exudate and pus released from swollen lymph node.

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14
Q

What is important to keep in mind about H.ducreyi?

A

Requires X factor (hematin) only.

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15
Q

How is Gardnerella vaginalis transmitted?

A

Sexually transmitted disease.

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16
Q

Has Gardnerella vaginalis capsule?

17
Q

Produce G.vaginalis exotoxins?

18
Q

What can G.vaginalis cause?

A

Bacterial vaginitis:

Foul smelling vaginal discharge (with fishy odor), vaginal pruritus, and often dysuria.

19
Q

How can we diagnose G.vaginalis infection?

A

Clue cells –> Vaginal epithelial cells that contain tiny pleomorphic gram (-) bacilli within the cytoplasm.

20
Q

What is important to keep in mind about G.vaginalis?

A

It does not require X or V factor for growth.

21
Q

How is Bordetella pertussis transmitted?

A

Via respiratory route - highly contagious.

22
Q

What is the virulence of B.pertussis?

A
  1. Capsule
  2. Beta-lactamase
  3. Filamentous hemagglutinin (FHA): A pili rod that extends from the surface of B.pertussis, enabling the bacteria to bind to ciliated epithelial cells of the bronchi.
23
Q

What are the toxins of B.pertussis?

A
  1. Pertussis toxin
  2. Extracytoplasmic adenylate cyclase
  3. Filamentous hemagglutinin
  4. Tracheal cytotoxin
24
Q

What does pertussis toxin do?

A

Activates G proteins that increase cAMP:

  1. Incr. Histamine sensitivity
  2. Incr. insulin release
  3. Incr. lymphocytes in blood
25
Q

What does extracytoplasmic adenylate cyclase do?

A

“Weakens” neutrophils, lymphocytes, and monocytes.

26
Q

What does filamentous hemagglutinin do?

A

Allows binding to ciliated epithelial cells.

27
Q

What does tracheal toxin do?

A

Kills ciliated epithelial cells.

28
Q

What can B.pertussis cause?

A

Whooping cough

29
Q

What happens in the catarrhal phase of whooping cough?

A

Patient is highly contagious (1-2 weeks).

  1. Low grade fever, runny nose and mild cough.
  2. Antibiotic susceptible during this stage.
30
Q

What happens during the paroxysmal phase of whooping cough?

A

2-10 weeks.

  1. Whoop (bursts of non-productive cough)
  2. Incr. lymphocytes in blood smear
  3. Antibiotics effective during this stage
31
Q

What is the last stage of whooping cough?

A

Covalescent stage

32
Q

How can we diagnose B.pertussis?

A
  1. Bordet-Gengou media
  2. Rapid serology - ELISA
  3. Direct fluorescein-labeled antibodies applied to nasopharyngeal specimens for rapid diagnosis
  4. PCR detection of bacterial DNA in respiratory secretions
33
Q

What are the high risk groups for B.pertussis infection?

A
  1. Infants less than one year old.

2. Adults (as immunity acquired from vaccines wears off).

34
Q

Where is Legionella pneumophila found?

A

Ubiquitous in man and natural water environments.

  1. Air conditioners
  2. Cooling towers
35
Q

What is the virulence of L.pneumophila?

A
  1. Facultative intracellular parasite
  2. Cu-Zn superoxide dysmutase and catalase-peroxidase protects from macrophage.
  3. Pili and flagella promote attachment and invasion.
  4. Secretion of protein toxins like RNAase, phospholipase A, and phospholipase C.
36
Q

What is the toxin of L.pneunophila?

A

Cytotoxin: kills hamster ovary cells.

37
Q

What can L.pneumophila cause?

A
  1. Pontiac fever

2. Legionnaires’ disease

38
Q

What happens in pontiac fever?

A
  1. Headache
  2. Fever
  3. Muscle aches and fatigue
  4. Self-limiting - recovery in a week is very common
39
Q

What happens in Legionnaires’ disease?

A
  1. Pneumonia
  2. Fever
  3. Non-productive cough
40
Q

How can we diagnose L.pneumophila?

A
  1. Culture on buffered charcoal yeast extract (L-cysteine is a critical ingredient).
  2. Serology (IFA and ELISA)
  3. Urinary antigen test - detects only L.pneumophila serogroup 1 (90% of cases).
41
Q

What is important to keep in mind about L.pneumophila?

A
  1. Facultative intracellular parasite: inside alveolar macrophages.
  2. Persons with compromised immune systems are especially suscpetible.

Microbiology (46 decks)

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