Pathology of Respiratory Tract Infections Flashcards
What are the common bacterial and viral organisms causing upper respiratory infections?
Bacteria:
Streptococcus pyogenes (Group A Streptococcus): Causes strep throat and pharyngitis.
Viruses:
Rhinovirus: Common cause of the common cold.
Adenovirus: Can cause pharyngitis, conjunctivitis, and colds.
Parainfluenza virus: Leads to croup in children and laryngotracheobronchitis.
Influenza virus: Causes flu, which can lead to viral pneumonia.
Epstein-Barr Virus (EBV): Causes mononucleosis (infectious mononucleosis), which can include pharyngitis and tonsillitis.
What are the key mechanisms of defence in the respiratory system?
Physical Barriers:
Nasal hairs and mucous trap pathogens.
Cilia in the upper airways move mucus and trapped particles out.
Cough reflex: Clears the airways of irritants and pathogens.
Mucosal Immune System:
IgA antibodies help neutralize pathogens.
Innate Immune Response:
Macrophages and neutrophils in the lungs fight infections.
Adaptive Immune Response:
T cells and B cells produce antibodies and enhance immune defense.
What is the pathogenesis of bronchopneumonia and lobar pneumonia?
Bronchopneumonia:
Infection begins in the bronchi and spreads to surrounding lung tissue.
Caused by bacteria like Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae.
Patchy consolidation in both lungs, typically seen in elderly or immunocompromised patients.
Lobar Pneumonia:
Involves consolidation of a whole lobe of the lung.
Commonly caused by Streptococcus pneumoniae.
Inflammatory exudates fill the alveoli, causing alveolar consolidation and impaired gas exchange.
What are the common complications and consequences of lower respiratory tract infections?
Pleural Effusion: Fluid accumulation in the pleural space.
Lung Abscess: A localized collection of pus due to infection.
Empyema: Infected pleural effusion containing pus.
Respiratory Failure: Due to impaired gas exchange or mechanical obstruction.
Sepsis: Can lead to multisystem organ failure if not treated.
Bronchiectasis: Chronic dilation of the bronchi due to recurrent infections.
What are the clinical features of acute bronchitis, pneumonia, and conditions like bronchiectasis, lung abscess, and empyema?
Acute Bronchitis:
Cough (usually productive), wheezing, mild fever, chest discomfort.
Caused by viruses like rhinovirus, influenza, and parainfluenza.
Pneumonia:
Fever, chills, productive cough, dyspnea, pleuritic chest pain, tachypnea.
Caused by bacteria like Streptococcus pneumoniae and viruses like influenza.
Bronchiectasis:
Chronic productive cough, hemoptysis, recurrent chest infections, dyspnea.
Lung Abscess:
Fever, night sweats, foul-smelling sputum, pleuritic chest pain.
Empyema:
Chest pain, fever, shortness of breath, decreased breath sounds.
What are some common causes of recurrent pneumonia?
Chronic Lung Diseases:
Chronic obstructive pulmonary disease (COPD), bronchiectasis.
Immune Deficiency:
HIV/AIDS, diabetes, organ transplantation.
Aspiration:
Inhalation of food, liquids, or vomit.
Smoking:
Damages respiratory defense mechanisms.
Inhalation of foreign bodies: Causes recurrent aspiration pneumonia.
Obstruction:
Due to tumors, bronchial strictures, or foreign bodies.
Microaspiration: Common in patients with gastroesophageal reflux disease (GERD).
What are the physiological changes to pulmonary gas exchange in respiratory tract infections?
Alveolar Inflammation:
Impaired gas exchange due to alveolar consolidation (pneumonia).
Decreased oxygen diffusion across the alveolar-capillary membrane.
Shunting:
Blood passes through non-ventilated areas, causing ventilation-perfusion mismatch.
Hypoxemia:
Reduced oxygen saturation in the blood, often due to decreased alveolar ventilation or increased dead space.
Hypercapnia:
Increased carbon dioxide in the blood, particularly in severe pneumonia or ARDS.
Increased Work of Breathing:
Due to airway obstruction, lung stiffness, or pleuritic pain.
