Lower Respiratory Tract Infections

Question 1

What makes up the lower respiratory tract?

Answer 1

Trachea
Bronchi
Bronchioles

Question 2

What is laryngitis and tracheitis?

Answer 2

Infection of the larynx and trachea
In adults, it causes hoarseness and burning pain
In children, it can cause the respiratory tract to narrow and become easily obstructed (requires hospitalization)

Question 3

What causes laryngitis and tracheitis?

Answer 3

Parainfluenza virus, RSV, influenza, adenovirus

Less commonly: H. influenzae

Question 4

What causes diphtheria?

Answer 4

Lysogenized strains of Corynebacterium diphtheria; this means it carries viral genome in the dormant strain. The viral genome codes for an AB toxin, which results in the arrest of protein synthesis in the target cells, which causes kills the epithelial cells and causes pseudo-memrbane formation

Question 5

How do we determine if someone is at risk diphtheria?

Answer 5

We do PCR or run an ELISA for the toxin

Question 6

What are complications due to diphtheria?

Answer 6

Myocarditis

Polyneuritis (paralysis of the soft palate and regurgitation of liquids)

Question 7

How is diphtheria treated?

Answer 7

Diphtheria is life-threatening and requires immediate action

An antitoxin, which is produced in horse serum, and antibiotics are given

Question 8

How is diphtheria prevented?

Answer 8

Vaccine, in combination with pertussis, tetanus, polio and Haemophilus influenzae B

Question 9

What causes pertussis?

Answer 9

Bordetella pertussis and Bordetella parapertussis (also B. bronchiseptica)

Question 10

How is pertussis transmitted?

Answer 10

It is highly transmissible (found in children)

It attaches to and multiplies in ciliated respiratory mucosa

Question 11

Describe the clinical manifestation of pertussis?

Answer 11

Characterized by paroxysms (continuous, uncontrollable) of coughing (whooping cough), which is the sum of several toxins
Fever is uncommon

Question 12

What are the toxins produced in pertussis?

Answer 12

Pertussis toxin
Adenylate cyclase
Tracheal toxin

Question 13

Describe the pertussis toxin; what does it do?

Answer 13

AB type toxin
A subunit: ADP-ribosyl transferase that catalyzes transfer of ADP-ribose from NAD to host cell proteins, affects signal transduction

Question 14

What does adenylate cyclase do in pertussis infection?

Answer 14

Enters neutrophils, causes increased cAMP which inhibits their chemotaxis, phagocytosis and bactericidal killing ability

Question 15

What does tracheal toxin do?

Answer 15

Kills tracheal cells

Question 16

What are complications that can result from pertussis infection?

Answer 16

Pneumonia (secondary infection); alveolar rupture
CNS effects (seizures)

Question 17

What are the three stages of pertussis infection?

Answer 17

Catarrhal
Paroxysmal
Convalescent

Question 18

Describe the catarrhal stage

Answer 18

Mild cold, runny nose, mild cough
Can last several weeks
Patient may not know that they have pertussis at this stage

Question 19

Describe the paroxysmal stage

Answer 19

Severe coughing begins (can last up to a minute)

15-25 paroxysmal fits/24 hours which causes vomiting and whooping

Question 20

Describe the convalescent stage

Answer 20

Slow decrease of symptoms after 4 weeks of infection

Question 21

How is pertussis infection prevented?

Answer 21

Acellular vaccines made of pertussis toxoid and bacterial components (filamentous hemagglutinin and fimbrae).
The vaccine is becoming less effective because of mutations in the protein structure (no production of polyclonal antibodies)

Question 22

What is bronchitis?

Answer 22

Inflammation of the tracheobronchial tree

Question 23

What causes bronchitis?

Answer 23

It is often viral (Rhinovirus, coronavirus, influenza virus, adenovirus)
Can be bacterial (Bordetella pertussis, B. parapertussis, Mycoplasma pneumoniae, Chlamydophila pneumoniae)

Question 24

When is bronchitis most common?

Answer 24

Peaks in winter

Question 25

What are the symptoms of bronchitis?

Answer 25

Cough, fever, variable amounts of sputum (sputum is a sign of LRT infection)

Question 26

Describe the pathogenesis of acute bronchitis

Answer 26

Usually follows upper respiratory tract infection

Spread causes damage to the respiratory epithelial cells by the same (usually viral) pathogens

Question 27

What are complications due to acute bronchitis?

Answer 27

Secondary bacterial infections (generally due to influenza)
Presentation varies; persistent bronchitis with increases sputum volume and purulence (instead of resolution) or pneumonia (which is usually community acquired)

Question 28

What are some of the long term consequences of acute bronchitis?

Answer 28

Pneumonia
Hepatitis
Encephalitis
Arthralgia
Skin lesions
Hemolytic anemia

Question 29

What is bronchiolitis?

Answer 29

Inflammation of the bronchioles. The bronchioles narrow and it is difficult to breath.
Restricted to childhood (usually children under 2 years)

Question 30

What is the number one cause of bronchiolitis and pneumonia in children under 2?

Answer 30

Respiratory Syncytial Virus (RSV)

Question 31

How is RSV transmitted?

Answer 31

Mostly by droplets and to some extent by hands
Once inhaled, it establishes infection in the nasopharynx and lower respiratory tract, causing bronchiolitis and/or pneumonia

Question 32

What are the symptoms of RSV?

Answer 32

Coughing
Fast respiratory rate
Cyanosis (coughing can result in the person not being able to breath)

Question 33

How is RSV infection diagnosed?

Answer 33

Detection of viral RNA obtained from throat swabs by PCR