Haemophilus, Bordetella, And Legionella

Question 0

How is H.influenza transmitted?

Answer 0

Via respiratory route.

Question 1

Where is H.influenza found?

Answer 1

Humans only.

Question 2

What is the virulence of H.influenza?

Answer 2

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

Question 3

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

Answer 3

b

Question 4

What are the toxins of H.influenza?

Answer 4

1. Cytolethal distending toxin (CDT)

2. Hemolysin

Question 5

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

Answer 5

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

Question 6

What can nonencapsulated H.influenza cause?

Answer 6

1. Otitis media
2. Sinusitis
3. COPD exacerbation and pneumonia

Question 7

How can we identify H.influenza?

Answer 7

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).

Question 8

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

Answer 8

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

• X factor: hematin
• V factor: NAD+

Question 9

How is Haemophilus ducreyi transmitted?

Answer 9

Sexually

Question 10

What are the toxins of H.ducreyi?

Answer 10

No exotoxins

Question 11

What can H.ducreyi cause?

Answer 11

Chancroid

Question 12

What is a chancroid?

Answer 12

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

Question 13

How can we identify H.ducreyi?

Answer 13

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

Question 14

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

Answer 14

Requires X factor (hematin) only.

Question 15

How is Gardnerella vaginalis transmitted?

Answer 15

Sexually transmitted disease.

Question 16

Has Gardnerella vaginalis capsule?

Answer 16

No.

Question 17

Produce G.vaginalis exotoxins?

Answer 17

No

Question 18

What can G.vaginalis cause?

Answer 18

Bacterial vaginitis:

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

Question 19

How can we diagnose G.vaginalis infection?

Answer 19

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

Question 20

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

Answer 20

It does not require X or V factor for growth.

Question 21

How is Bordetella pertussis transmitted?

Answer 21

Via respiratory route - highly contagious.

Question 22

What is the virulence of B.pertussis?

Answer 22

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.

Question 23

What are the toxins of B.pertussis?

Answer 23

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

Question 24

What does pertussis toxin do?

Answer 24

Activates G proteins that increase cAMP: 1. Incr. Histamine sensitivity 2. Incr. insulin release 3. Incr. lymphocytes in blood

Question 25

What does extracytoplasmic adenylate cyclase do?

Answer 25

"Weakens" neutrophils, lymphocytes, and monocytes.

Question 26

What does filamentous hemagglutinin do?

Answer 26

Allows binding to ciliated epithelial cells.

Question 27

What does tracheal toxin do?

Answer 27

Kills ciliated epithelial cells.

Question 28

What can B.pertussis cause?

Answer 28

Whooping cough

Question 29

What happens in the catarrhal phase of whooping cough?

Answer 29

Patient is highly contagious (1-2 weeks). 1. Low grade fever, runny nose and mild cough. 2. Antibiotic susceptible during this stage.

Question 30

What happens during the paroxysmal phase of whooping cough?

Answer 30

2-10 weeks. 1. Whoop (bursts of non-productive cough) 2. Incr. lymphocytes in blood smear 3. Antibiotics effective during this stage

Question 31

What is the last stage of whooping cough?

Answer 31

Covalescent stage

Question 32

How can we diagnose B.pertussis?

Answer 32

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

Question 33

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

Answer 33

1. Infants less than one year old. | 2. Adults (as immunity acquired from vaccines wears off).

Question 34

Where is Legionella pneumophila found?

Answer 34

Ubiquitous in man and natural water environments. 1. Air conditioners 2. Cooling towers

Question 35

What is the virulence of L.pneumophila?

Answer 35

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.

Question 36

What is the toxin of L.pneunophila?

Answer 36

Cytotoxin: kills hamster ovary cells.

Question 37

What can L.pneumophila cause?

Answer 37

1. Pontiac fever | 2. Legionnaires' disease

Question 38

What happens in pontiac fever?

Answer 38

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

Question 39

What happens in Legionnaires' disease?

Answer 39

1. Pneumonia 2. Fever 3. Non-productive cough

Question 40

How can we diagnose L.pneumophila?

Answer 40

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).

Question 41

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

Answer 41

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