Haemophilus and Bordetella

Question 1

Cellular characteristics of Haemophilus influenzae?

Answer 1

• Gram (-)
• Non motile
• Non-spore forming
• Only grows on chocolate agar with Factors X and V
• Respiratory droplets
• Two forms - encapsulated and unencapsulated

Question 2

Characteristics of high pathogenicity strain of H. influenzae?

Answer 2

Polysaccharaide capsule

Question 3

Which type of H. influenze causes the worse diease?

Answer 3

Type B (Hib)

Question 4

What is the target of the vaccine for H.influenzae?

Answer 4

The Hib capsule of polyribosyl ribitol phosphate

Question 5

What is the target of the vaccine in NTHi?

Answer 5

Vaccine does not cover unencapsulated strains

Question 6

How is H. influenzae similar to N. meningitidis?

Answer 6

Capsule fns in immune evasion

Question 7

Describe Hib pathogenesis?

Answer 7

1. Colonization of resp. mucosa via IgA protease
2. Once estab. in resp. mucosa, invades bloodstream

Question 8

What determines severity of Hib illness?

Answer 8

Magnitude and Duration of bacteremia

Question 9

When is the peak risk for Hib infection?

Answer 9

6 mo to 1 yr - mother’s Ab wane, child can’t raise strong defense

Question 10

Describe the NTHi pathogenesis

Answer 10

1. NTHi utilizes pili, attachment proteins and IgA protease to invade

Question 11

What patients are particular susceptible to NTHi?

Answer 11

1. Patient’s with CF b/c bug can easily create a biofilm

Question 12

Disease caused by H. influenzae

Answer 12

1. Menigitis
2. Cellulitis
3. Otitis media and sinusitis
4. Epiglottitis - Cherry Red epiglottis
5. Septic arthritis

Question 13

Dx procedure for Hib epitlottitis?

Answer 13

On exam, cherry red epiglottis is seen along with progressive respiratory difficulty, inability to swallow. Once airway secured, lateral neck radiograph is taken

Question 14

What patients are NTHi associated with?

Answer 14

Neonates and postpartum women

Question 15

What type of NTHi is particularly virulent?

Answer 15

Biotype 4

Question 16

Procedure for H. influenzae Dx?

Answer 16

Culture on chocoalte agar with factors X and V; Growth on factor only agar is sufficient for Dx

Question 17

Tx for H. influenzae meningitis?

Answer 17

Ceftriaxone and in children > 2 mo, add Dexamethasone

Question 18

Tx for H. influenzae Upper Respiratory infection?

Answer 18

Amoxicillin + clavulanate or trimethoprim+sulfamethoxazole

Question 19

Primary preventive method for H. influenzae?

Answer 19

Vaccine early!

Question 20

Cellular characteristics of Bortedella Pertussis?

Answer 20

• Encapsulated
• G (-)
• Human-restricted

Question 21

Characteristics of Pertussis disease?

Answer 21

• Whooping cough
• Highly contagious

Question 22

Pathogenesis of B. pertussis?

Answer 22

1. Filamentous hemagglutinin pilus attaches bac. to cilia of epithelial cells lining resp. tract
2. Pertussis toxin A-B subunit ADP-ribosylator kills ciliated cells, and inhibits chemokine signal transduction = lymphocytosis
3. Tracheal cytotoxin - Kills ciliated cells as well

Question 23

What allows B. pertussis to be so virulent?

Answer 23

1. Kills ciliated cells allowing for further bac. growth
2. Production of mucopurulosanguineous exudate compromising small airways
3. Both allow for paroxysmal cough and spread via many aerosol droplets

Question 24

Pertussis Px?

Answer 24

• Do bacteremia
• Px good, complications minimal
• Major complication comes from infants deprived of oxygen

Question 25

Typical presentation of pertussis?

Answer 25

Afebrile, **dehydrated**, Hx of incomplete/absent vaccination

Question 26

3 stages of pertussis?

Answer 26

1. **Catarrhal -** Nonspecific upper resp. Syx: Congestion, sneezing, rhinorrea, maximally contagious 2. **Paroxysmal** - **Intense coughing**: Series of hacking cough, copious mucus production, **inspiratory whoop** 3. **Convalescence**: Free of bugs but fatigue and **chronic cough** because bugs killed ciliated cells

Question 27

How can whoop be absent in adults?

Answer 27

Adult airway is large and may not be as obstructed

Question 28

Lab tests for B. pertussis?

Answer 28

1. Pronounced leukocytosis (70% lymphocytes) 2. **Bordet-Gengou** agar - but bugs are fastidious

Question 29

Tx for Pertussis?

Answer 29

Macrolides, supportive care b/c of dead ciliated cells

Question 30

Pertussis management in infants

Answer 30

Supplemental O2, mucus suctioning

Question 31

Pertussis prevention?

Answer 31

1. Acellular vaccine - genetically-inactivated Pertussi toxoid, filamentous hemagglutinin, pertactin, fibriae types 2 and 3 (Used in US) 2. Killed vaccine - whole heat-killed, believed risk of encephalopathy 3. **10 year boosters needed for either vaccine**

Question 32

Tx for unvaccinated exposed individuals?

Answer 32

Erythromycin