Bronchitis - Introduction, Acute bronchitis, Chronic bronchitis
Introduction to Bronchitis
Bronchitis is an infection of the main airways of the lungs (bronchi) resulting in inflation and irritation of the bronchus. It can be divided into two types based on the durability of the infection.
Acute bronchitis
Chronic bronchitis
Acute bronchitis
Acute bronchitis is characterized by inflammation of the tracheobronchial tree. It may be a part of or preceded by upper RTI such as influenzae (the “flu”) or the common cold.
Pathogenesis of acute bronchitis has no specific etiological agent but is a mixture of viral cytopathic events and a response by the host immune system. The protective functions of the bronchial epithelium are disturbed and excess fluid accumulates in the bronchi.
Depending on the etiology, destruction of the bronchial epithelium may be either extensive (eg. influenzae virus) or minimal (eg. rhinovirus colds).
Clinically, bronchitis is characterized by cough, variable fever, and sputum production. Sputum (pus from the lungs) is often clear at the onset but may become purulent as the illness persists. Bronchitis may also manifest as croup (a clinical concentration marked by a barking cough or hoarseness).
They are not related to long-term etiologies causing damage to the lungs but are typically a result of infectious pertussis. The best specimen for the diagnosis of pertussis is a deep nasopharyngeal specimen collected with a calcium alginate swab.
Major causes of acute bronchitis
Both bacteria and viruses can cause acute bronchitis.
Bacteria:
Bordetella pertussis (in infants and school children)
B. parapertussis
Mycoplasma pneumoniae
Chlamydia pneumoniae
Viruses: commonly influenzae virus, adenovirus, rhinovirus, coronavirus
less commonly = RSV, human metapneumovirus, coxsackie A21 virus
Chronic bronchitis
Chronic bronchitis is common conduction affecting about 10-25% of adults. This disease is defined by clinical symptoms in which excessive mucus production leads to coughing up sputum on most days for at least 3 consecutive months for more than 2 successive years.
Cigarette smoking, infection, and inhalation of dust or fumes are important contributing factors, and patients with chronic bronchitis can suffer from acute flare-ups of infection.
Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis are frequently cultured from the bronchi of these patients.
If acute bronchitis is present along with chronic one, it is difficult to incriminate this organism as the specific cause although viruses are frequent causes of acute bronchitis.