Lower Respiratory Tract Infections Flashcards
What makes up the lower respiratory tract?
Trachea
Bronchi
Bronchioles
What is laryngitis and tracheitis?
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)
What causes laryngitis and tracheitis?
Parainfluenza virus, RSV, influenza, adenovirus
Less commonly: H. influenzae
What causes diphtheria?
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
How do we determine if someone is at risk diphtheria?
We do PCR or run an ELISA for the toxin
What are complications due to diphtheria?
Myocarditis
Polyneuritis (paralysis of the soft palate and regurgitation of liquids)
How is diphtheria treated?
Diphtheria is life-threatening and requires immediate action
An antitoxin, which is produced in horse serum, and antibiotics are given
How is diphtheria prevented?
Vaccine, in combination with pertussis, tetanus, polio and Haemophilus influenzae B
What causes pertussis?
Bordetella pertussis and Bordetella parapertussis (also B. bronchiseptica)
How is pertussis transmitted?
It is highly transmissible (found in children)
It attaches to and multiplies in ciliated respiratory mucosa
Describe the clinical manifestation of pertussis?
Characterized by paroxysms (continuous, uncontrollable) of coughing (whooping cough), which is the sum of several toxins
Fever is uncommon
What are the toxins produced in pertussis?
Pertussis toxin
Adenylate cyclase
Tracheal toxin
Describe the pertussis toxin; what does it do?
AB type toxin
A subunit: ADP-ribosyl transferase that catalyzes transfer of ADP-ribose from NAD to host cell proteins, affects signal transduction
What does adenylate cyclase do in pertussis infection?
Enters neutrophils, causes increased cAMP which inhibits their chemotaxis, phagocytosis and bactericidal killing ability
What does tracheal toxin do?
Kills tracheal cells
What are complications that can result from pertussis infection?
Pneumonia (secondary infection); alveolar rupture CNS effects (seizures)
What are the three stages of pertussis infection?
Catarrhal
Paroxysmal
Convalescent
Describe the catarrhal stage
Mild cold, runny nose, mild cough
Can last several weeks
Patient may not know that they have pertussis at this stage
Describe the paroxysmal stage
Severe coughing begins (can last up to a minute)
15-25 paroxysmal fits/24 hours which causes vomiting and whooping
Describe the convalescent stage
Slow decrease of symptoms after 4 weeks of infection
How is pertussis infection prevented?
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)
What is bronchitis?
Inflammation of the tracheobronchial tree
What causes bronchitis?
It is often viral (Rhinovirus, coronavirus, influenza virus, adenovirus)
Can be bacterial (Bordetella pertussis, B. parapertussis, Mycoplasma pneumoniae, Chlamydophila pneumoniae)
When is bronchitis most common?
Peaks in winter
What are the symptoms of bronchitis?
Cough, fever, variable amounts of sputum (sputum is a sign of LRT infection)
Describe the pathogenesis of acute bronchitis
Usually follows upper respiratory tract infection
Spread causes damage to the respiratory epithelial cells by the same (usually viral) pathogens
What are complications due to acute bronchitis?
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)
What are some of the long term consequences of acute bronchitis?
Pneumonia Hepatitis Encephalitis Arthralgia Skin lesions Hemolytic anemia
What is bronchiolitis?
Inflammation of the bronchioles. The bronchioles narrow and it is difficult to breath.
Restricted to childhood (usually children under 2 years)
What is the number one cause of bronchiolitis and pneumonia in children under 2?
Respiratory Syncytial Virus (RSV)
How is RSV transmitted?
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
What are the symptoms of RSV?
Coughing
Fast respiratory rate
Cyanosis (coughing can result in the person not being able to breath)
How is RSV infection diagnosed?
Detection of viral RNA obtained from throat swabs by PCR
