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Infectious Disease and Microbiology – Bronchitis
Bronchitis is inflammation of the lining of the tracheobronchial tree and is classified as acute or chronic. Acute bronchitis is defined by cough, with or without sputum production, lasting less than three weeks. Chronic bronchitis is clinically defined as a productive cough for at least three months in each of two consecutive years and is a major component of chronic obstructive pulmonary disease (COPD).
Chronic bronchitis affects approximately 9.5 million Americans annually, while around 10 million people seek medical care for acute bronchitis each year. Acute bronchitis occurs in all age groups and affects males and females equally. Chronic bronchitis is most prevalent in individuals older than 50 years and is more common in males.
Risk factors for acute bronchitis include cigarette smoking, exposure to respiratory irritants such as air pollution and gases, recent upper respiratory tract infections, chronic lung disease, older age, and decreased immunity. Chronic bronchitis is strongly associated with long-term smoking and environmental pollutants, as well as recurrent respiratory infections, allergies, and advancing age. Genetic factors have a moderate influence on the development of chronic bronchitis.
Preventive strategies focus on smoking cessation and avoidance of secondhand smoke and environmental irritants. Reducing exposure to individuals with respiratory infections is important. Annual influenza vaccination and pneumococcal vaccination every 5–10 years in individuals aged 65 years or older or those with chronic disease are recommended.
The pathophysiology involves irritation of the bronchial mucosa, leading to hyperemia, edema, and excessive mucus production. Bronchial smooth muscle hyperreactivity results in bronchospasm. Increased airflow resistance can lead to hypoventilation, hypercapnia, and hypoxemia. In chronic bronchitis, goblet cell hyperplasia, mucus plugging, smooth muscle hyperplasia, and persistent inflammatory cell infiltration are characteristic findings.
Acute bronchitis is most commonly viral, caused by influenza A and B viruses, parainfluenza virus, respiratory syncytial virus, coronavirus, adenovirus, and rhinovirus. Atypical bacteria such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis may also be responsible. Chronic bronchitis is primarily caused by smoking and environmental pollutants. Acute exacerbations of chronic bronchitis are frequently associated with Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, viral infections, and, in patients with severe lung impairment, Pseudomonas aeruginosa and Enterobacteriaceae.
Patients with acute bronchitis often report a recent cold or sinus infection, exposure to irritants, or smoking history. Symptoms include cough, mild fever, sore throat, dyspnea on exertion, wheezing, chest tightness, fatigue, and malaise. Chronic bronchitis presents with persistent productive cough. Acute exacerbations are characterized by increased dyspnea, increased sputum production, and increased sputum purulence. On physical examination, fever is uncommon. Findings may include tachypnea, tachycardia, coarse breath sounds, wheezing, and prolonged expiration. Worsening respiratory function is typical during acute exacerbations.
Laboratory evaluation may include a complete blood count and sputum cultures when bacterial infection is suspected. Serum procalcitonin levels may help guide antibiotic therapy decisions. Pulse oximetry and arterial blood gas analysis are useful in more severe cases. Chest radiography is performed to exclude pneumonia. Spirometry is recommended after recovery to assess lung function and airway obstruction, especially in suspected chronic bronchitis.
The differential diagnosis includes asthma, bronchiolitis, pneumonia, pharyngitis, bronchiectasis, chronic sinusitis, pulmonary embolism, congestive heart failure, sarcoidosis, atelectasis, chemical pneumonitis, and gastroesophageal reflux disease.
Management of acute bronchitis is generally supportive, as most cases are viral. Antiviral therapy such as oseltamivir or zanamivir is indicated for confirmed influenza. For Bordetella pertussis infection, azithromycin, erythromycin, or clarithromycin is recommended, with trimethoprim–sulfamethoxazole as a second-line option. Antibiotics are not routinely indicated for uncomplicated acute bronchitis. In acute bacterial exacerbations of chronic bronchitis, antibiotics such as amoxicillin, amoxicillin–clavulanate, trimethoprim–sulfamethoxazole, doxycycline, macrolides, or fluoroquinolones may be prescribed for 5–10 days. Bronchodilators can relieve dyspnea, systemic corticosteroids may be used during exacerbations, and low-flow oxygen therapy is indicated for hypoxemia. Antitussives such as codeine or dextromethorphan may provide short-term symptomatic relief.
Most patients with acute bronchitis have an excellent prognosis. Smoking cessation slows the progression of chronic bronchitis and improves outcomes. Complications may include respiratory failure, pulmonary emphysema, right heart failure, and treatment failure due to advanced disease, incorrect diagnosis, inadequate antibiotic dosing, immunocompromised state, or resistant organisms such as Pseudomonas. Regular follow-up, spirometry in chronic cases, patient education, and environmental modification are essential components of long-term management.
Bronchitis is inflammation of the lining of the tracheobronchial tree and is classified as acute or chronic. Acute bronchitis is defined by cough, with or without sputum production, lasting less than three weeks. Chronic bronchitis is clinically defined as a productive cough for at least three months in each of two consecutive years and is a major component of chronic obstructive pulmonary disease (COPD).
Chronic bronchitis affects approximately 9.5 million Americans annually, while around 10 million people seek medical care for acute bronchitis each year. Acute bronchitis occurs in all age groups and affects males and females equally. Chronic bronchitis is most prevalent in individuals older than 50 years and is more common in males.
Risk factors for acute bronchitis include cigarette smoking, exposure to respiratory irritants such as air pollution and gases, recent upper respiratory tract infections, chronic lung disease, older age, and decreased immunity. Chronic bronchitis is strongly associated with long-term smoking and environmental pollutants, as well as recurrent respiratory infections, allergies, and advancing age. Genetic factors have a moderate influence on the development of chronic bronchitis.
Preventive strategies focus on smoking cessation and avoidance of secondhand smoke and environmental irritants. Reducing exposure to individuals with respiratory infections is important. Annual influenza vaccination and pneumococcal vaccination every 5–10 years in individuals aged 65 years or older or those with chronic disease are recommended.
The pathophysiology involves irritation of the bronchial mucosa, leading to hyperemia, edema, and excessive mucus production. Bronchial smooth muscle hyperreactivity results in bronchospasm. Increased airflow resistance can lead to hypoventilation, hypercapnia, and hypoxemia. In chronic bronchitis, goblet cell hyperplasia, mucus plugging, smooth muscle hyperplasia, and persistent inflammatory cell infiltration are characteristic findings.
Acute bronchitis is most commonly viral, caused by influenza A and B viruses, parainfluenza virus, respiratory syncytial virus, coronavirus, adenovirus, and rhinovirus. Atypical bacteria such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Bordetella pertussis may also be responsible. Chronic bronchitis is primarily caused by smoking and environmental pollutants. Acute exacerbations of chronic bronchitis are frequently associated with Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, viral infections, and, in patients with severe lung impairment, Pseudomonas aeruginosa and Enterobacteriaceae.
Patients with acute bronchitis often report a recent cold or sinus infection, exposure to irritants, or smoking history. Symptoms include cough, mild fever, sore throat, dyspnea on exertion, wheezing, chest tightness, fatigue, and malaise. Chronic bronchitis presents with persistent productive cough. Acute exacerbations are characterized by increased dyspnea, increased sputum production, and increased sputum purulence. On physical examination, fever is uncommon. Findings may include tachypnea, tachycardia, coarse breath sounds, wheezing, and prolonged expiration. Worsening respiratory function is typical during acute exacerbations.
Laboratory evaluation may include a complete blood count and sputum cultures when bacterial infection is suspected. Serum procalcitonin levels may help guide antibiotic therapy decisions. Pulse oximetry and arterial blood gas analysis are useful in more severe cases. Chest radiography is performed to exclude pneumonia. Spirometry is recommended after recovery to assess lung function and airway obstruction, especially in suspected chronic bronchitis.
The differential diagnosis includes asthma, bronchiolitis, pneumonia, pharyngitis, bronchiectasis, chronic sinusitis, pulmonary embolism, congestive heart failure, sarcoidosis, atelectasis, chemical pneumonitis, and gastroesophageal reflux disease.
Management of acute bronchitis is generally supportive, as most cases are viral. Antiviral therapy such as oseltamivir or zanamivir is indicated for confirmed influenza. For Bordetella pertussis infection, azithromycin, erythromycin, or clarithromycin is recommended, with trimethoprim–sulfamethoxazole as a second-line option. Antibiotics are not routinely indicated for uncomplicated acute bronchitis. In acute bacterial exacerbations of chronic bronchitis, antibiotics such as amoxicillin, amoxicillin–clavulanate, trimethoprim–sulfamethoxazole, doxycycline, macrolides, or fluoroquinolones may be prescribed for 5–10 days. Bronchodilators can relieve dyspnea, systemic corticosteroids may be used during exacerbations, and low-flow oxygen therapy is indicated for hypoxemia. Antitussives such as codeine or dextromethorphan may provide short-term symptomatic relief.
Most patients with acute bronchitis have an excellent prognosis. Smoking cessation slows the progression of chronic bronchitis and improves outcomes. Complications may include respiratory failure, pulmonary emphysema, right heart failure, and treatment failure due to advanced disease, incorrect diagnosis, inadequate antibiotic dosing, immunocompromised state, or resistant organisms such as Pseudomonas. Regular follow-up, spirometry in chronic cases, patient education, and environmental modification are essential components of long-term management.
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