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Haemophilus Influenzae Flashcards

1
Q

What is the gram strain and morphology of H. influenzae?

A

Gram-negative coccobacillus

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2
Q

T/F. H. influeza is nonmotile and non-spore-forming.

A

True

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3
Q

What does the genus name Haemophilus mean?

A

Blood-loving

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4
Q

What two supplements are required for the aerobic growth of H. influenza?

A

X factor and V factor

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5
Q

This is a heat-stable iron-containing pigment required for H. influenzae to make cytochromes. Provides protoporphyrins, essential for heme biosynthesis.

A

X factor

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6
Q

This is a heat-labile coenzyme required for metabolic processes. Can be NAD or NADP. Found inside red blood cells.

A

V factor

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7
Q

Why does H. influenzae exhibit satellitism around colonies of hemolytic S. aureus?

A

It provides V factor

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8
Q

What are the key characteristics of Haemophilus influenzae colonies?

A

Granular, transparent (or slightly opaque), circular, and dome-shaped

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9
Q

How do encapsulated strains of H. influenzae appear?

A

Mucoid and iridescent

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10
Q

Which capsular type is an important invasive pathogen in humans?

A

Capsular type b

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11
Q

What is H. influenzae’s capsule made of?

A

Polyribosylribitol phosphate

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12
Q

Why are some H. influenzae strains called nontypeable?

A

Because they lack a polysaccharide capsule

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13
Q

For which antibody does H. influenzae has a protease?

A

IgA

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14
Q

T/F. H. influenzae is exclusively recovered from humans.

A

True

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15
Q

How is Haemophilus influenzae transmitted?

A
  • Airborne droplets
  • Direct contact with secretions
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16
Q

What is the first step in Haemophilus influenzae infection leading to otitis media?

A

Colonization of the upper respiratory tract

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17
Q

What molecules does H. influenzae use to adhere to host cells?

A

Adhesins

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18
Q

How do type b strains of H. influenzae spread in the body?

A

They can get access to the bloodstream

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19
Q

How do nontypeable strains of H. influenzae primarily cause disease?

A

Local invasion of mucosal surfaces

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20
Q

What bacterial components released by H. influenzae trigger host inflammation in otitis media?

A
  • Lipooligosaccharide
  • Lipoproteins
  • Peptidoglycan fragments
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21
Q

What key virulence genes are more common in otitis media strains of H. influenzae?

A
  • Lipooligosaccharide synthesis gene (lic2B)
  • Histidine operon
  • Urease operon
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22
Q

What mechanism allows nontypeable H. influenzae to rapidly and reversibly regulate virulence gene expression?

A

Phase variation (involves methylation of DNA)

23
Q

What are the most common diseases caused by nontypeable H. influenzae?

A
  • Otitis media
  • Sinusitis
  • Conjunctivitis
  • Tracheobronchitis
  • Pneumonia
24
Q

What are the most common diseases caused by H. influenzae type b?

A
  • Meningitis
  • Epiglottitis
  • Bacteremia
25
T/F. Pneumonia caused by H. influenzae type b is now less common due to vaccination.
True
26
Where is Haemophilus influenzae found in biofilm form?
Middle ear
27
What part of the respiratory tract is chronically colonized by nontypeable H. influenzae in COPD patients?
Lower respiratory tract
28
What is the most common bacterial cause of COPD exacerbations?
Nontypeable H. influenzae
29
In which age group is otitis media most common for nontypeable H. influenzae?
Children aged 6 months to 5 years
30
What are the symptoms of otitis media in infants?
Fever, irritability and ear pain
31
Compared to S. pneumoniae, what symptoms are less likely in nontypeable H. influenzae otitis media?
Fever and otorrhea
32
In which populations is nontypeable H. influenzae a common cause of pneumonia?
* Older adults * Individuals with COPD * Those with immunodefficiency
33
What condition is nontypeable H. influenzae a common cause of in the sinuses?
Acute maxillary sinusitis
34
What is the most serious acute manifestation of systemic H. influenzae type b infection?
Meningitis
35
What symptoms often precede H. influenzae type b meningitis?
Upper respiratory infection symptoms
36
In which adults is H. influenzae type b meningitis more likely to occur?
Those with: * Recent or remote head trauma * Prior neurosurgery * Paranasal sinusitis * Otitis * CSF leak
37
What are the common signs of H. influenzae type b meningitis?
* Fever * Altered CNS function
38
Why can nuchal rigidity be absent in young children with H. influenzae type b meningitis?
Because they often lack specific meningeal signs early in the disease.
39
What complications may develop as H. influenzae type b meningitis progresses?
* Seizures * Coma * Subdural effusion
40
What signs should clinicians look for in older children with H. influenzae type b meningitis?
* Papilledema * Altered mental status
41
Acute respiratory obstruction caused by cellulitis of supraglottic tissues, a potentially lethal disease with fulminating onset. Caused by H. influenzae type b.
Epiglottitis
42
What age group is primarily affected by H. influenzae type b acute respiratory obstruction?
Children aged 2-7 years
43
What is the characteristic appearance of the epiglottis in H. influenzae type b acute respiratory obstruction?
Cherry red epiglottis
44
In which age group are primary lung infections by H. influenzae type b most common?
Children aged 4 months to 4 years
45
During which seasons does H. influenzae type b pneumonia most commonly occur?
Winter or spring
46
What type of pneumonia does H. influenzae type b typically cause?
Severe consolidative pneumonia
47
How does H. influenzae type b pneumonia differ from other bacterial pneumonias (e.g., S. aureus, S. pneumoniae)?
* More insidious onset * Severe dyspnea * Tachycardia * Pericarditis
48
Diagnosis for nontypeable H. influenzae.
Culture
49
From which samples can microbiologic studies be made to diagnose H. influenzae type b?
* Blood * CSF * Other sterile fluids
50
Active oral antibiotics against nontypeable H. influenzae.
* Amoxicillin-clavulanate * Fluoroquinolones * Macrolides * Cephalosporins
51
Antibiotics prescribed fot mores serious infections caused by nontypeable H. influenzae.
Parenteral agents: * Cephalosporins * Ampicillin-sulbactam * Fluoroquinolones
52
First-line regimen for H. influenzae type b.
Cefotaxime or ceftriaxone
53
T/F. There is currently a conjugated vaccine available for H. influenzae type b.
True

Infectious diseases pathophysiology (13 decks)

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