Pathology of Pneumonia

Pathology of Pneumonia: Causes, Symptoms, and Treatment

• Pneumonia is an inflammatory reaction of the alveoli and interstitium of the lung, usually caused by an infectious agent.
• The pathological features of acute pneumonia include inflammatory exudate in the alveolar space that consolidates and inflammation of alveolar septa, leading to the consolidation of affected areas.
• The most common causative agents of acute pneumonia are bacteria, viruses, mycoplasma, fungi, and inorganic agents.
• The routes of infection for acute pneumonia include aspiration of oropharyngeal secretions/gastric contents, inhalation of pathogens, contamination from systemic circulation, alcohol, and cigarette smoke.
• Pneumonia can be classified anatomically, clinically, and microbiologically, with the most clinically relevant classification based on the circumstances surrounding the development of pneumonia.
• The sub-divisions of pneumonia include community-acquired pneumonia, hospital-acquired or nosocomial pneumonia, immuno-compromised pneumonia, aspiration pneumonia, necrotizing pneumonia and lung abscess, and chronic pneumonia.
• Streptococcus pneumoniae is the most common causative agent of community-acquired pneumonia, while Staphylococcus aureus, Enterobacteriacae & Pseudomonas species are common in hospital-acquired pneumonia.
• Aspiration of gastric contents can cause pneumonia due to both irritation of gastric contents and bacteria, with anaerobic bacteria and aerobic bacteria such as S pneumoniae, S aureus, H influenza, Pseudomonas aeruginosa being the most common causative agents.
• Symptoms of acute bacterial pneumonia include fever, chills, dyspnea, cough with or without sputum, crackles on auscultation, and consolidation in radiograph.
• Diagnosis of acute bacterial pneumonia can be made through sputum analysis, X-ray, and FBC, and treatment involves antibiotic therapy.
• Possible outcomes of pneumonia include resolution, organization, abscess formation, empyema, bacteremia, and death.
• Chronic pneumonia is often a localized lesion in an immunocompromised patient, typically caused by bacteria such as Mycobacterium tuberculosis or fungi such as Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidiodies immitis.

Pathology of Pneumonia

• Pneumonia is an inflammatory reaction of the alveoli and interstitium of the lung usually caused by an infectious agent.
• Acute pneumonia is characterized by inflammatory exudate in the alveolar space that consolidates and inflammation of alveolar septa.
• The most common causative organisms of pneumonia are bacteria (Gram +ve: S pneumoniae, Staphylococcus aureus; Gram –ve: Haemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila), viruses, mycoplasma, fungi, and inorganic agents.
• Pneumonia can be acquired through aspiration of oropharyngeal secretions/gastric contents, inhalation of pathogens, or contamination from systemic circulation.
• Pneumonia can be classified anatomically, clinically, or microbiologically, with the most clinically relevant classification based around the circumstances surrounding the development of pneumonia.
• Community-acquired pneumonia (CAP) is the most common type, caused by Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Legionella pneumophila, and viruses.
• Hospital-acquired pneumonia (nosocomial) is serious and often life-threatening, caused by Staphylococcus aureus, Enterobacteriacae & Pseudomonas species, and often occurs in patients with underlying diseases, immunosuppression, prolonged antibiotic therapy, invasive access devices, or mechanical ventilators.
• Immuno-compromised patients are at risk of opportunistic infections, such as Mycobacterial infection, Cytomegalovirus (CMV), Herpes simplex, Pneumocystis jiroveci, Candida, and Aspergillus, in addition to usual bacterial/viral/fungal organisms.
• Aspiration pneumonia is due to the aspiration of gastric contents and bacteria, often caused by abnormal gag/swallow reflexes, unconsciousness, repeated vomiting, or poor oral hygiene.
• Necrotizing pneumonia and lung abscess are complications/progressions of pneumonia, frequently causing death, but can resolve with antimicrobial therapy leaving a scar.
• Symptoms of acute bacterial pneumonia include fever, chills, dyspnea, cough with or without sputum, crackles on auscultation, and consolidation in radiograph, with diagnosis through sputum analysis, X-ray, and FBC, and treatment with antibiotics.
• Possible outcomes of pneumonia include resolution, organization, abscess formation, empyema, bacteremia, and death. Chronic pneumonia is often a localized lesion in an immunocompromised patient, typically caused by bacteria (e.g., Mycobacterium tuberculosis) or fungi.

Test your knowledge on the pathology of pneumonia with this informative quiz. Learn about the causes, symptoms, and treatment options for this inflammatory lung condition. Explore the different types of pneumonia and their classifications based on anatomy, clinical presentation, and microbiology. Identify the most common causative agents of pneumonia and their routes of infection. Discover the possible outcomes of pneumonia and how to diagnose and treat it effectively. Sharpen your understanding of this important respiratory disease and take the quiz now.