Pathology of Pneumonia PDF

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Document Details

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The University of Nottingham

Dr Marie Kokolski

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pneumonia pathology respiratory infection pulmonary disease medical presentation

Summary

This document presents an overview of the pathology of pneumonia, including acute and chronic forms. It details causative agents, routes of infection and classifications of different pneumonia types. The presentation also provides an analysis of clinical symptoms and outlines common treatment and outcomes, covering a range of cases (including immunocompromised patients and those with aspiration or hospital-acquired pneumonia).

Full Transcript

Pathology of Pneumonia DR MARIE KOKOLSKI Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • De...

Pathology of Pneumonia DR MARIE KOKOLSKI Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • Describe the causative agents of chronic pneumonia Pneumonia v First described by Hippocrates (460-370 BC) v Around 220,000 people receive a diagnosis of pneumonia each year v 6th biggest cause of death in the UK and 3rd biggest case of death from lung disease v Accounts for more hospital admissions and ‘bed days’ than any other lung disease Annual number of deaths Coverage of pneumococcal vaccine Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • Describe the causative agents of chronic pneumonia Acute pneumonia Inflammatory reaction of the alveoli and interstitium of the lung usually caused by an infectious agent Characterised by ◦ Inflammatory exudate in the alveolar space that consolidates ◦ Inflammation of alveolar septa Leading cause of death from an infectious disease. Fifth most common cause of death in the US Histology NORMAL Pneumonia: Neutrophils and fluid in alveoli, congested capillaries (Red Hepatization) Organisation: exudates transformed to masses: macrophages and fibroblasts. Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • Describe the causative agents of chronic pneumonia Causative organism •Bacteria – Gram +ve: S pneumoniae, Staphylococcus aureus – Gram –ve: Haemophilus influenzae , Klebsiella pneumoniae, Legionella pneumophila • Viruses • Mycoplasma: Mycobacterium tuberculosis • Fungi: Pneumocystis jiroveci • Inorganic agents (inhaled dusts or gases) Routes of infection Aspiration of oropharyngeal secretions/gastric contents (25-35%) Inhalation of pathogens Contamination from systemic circulation Alcohol: impairs cough reflex, increased aspiration Cigarette smoke: reduced mucociliary and macrophage action Classification of pneumonia Anatomical classification – how has the infection spread in the lungs? Clinical setting in which disease occurs – what are the circumstances surrounding the disease? Microbiological – Identifying the causative agent The most clinically relevant classification is based around the circumstances surrounding the development of pneumonia Anatomical ◦ Lobar pneumonia: alveoli-alveoli ◦ Organisms access alveoli and rapidly spread via alveolar pores (connect adjacent alveoli) ◦ Adult - poor hygiene/malnourished/alcoholic ◦ Bronchopneumonia: Bronchi to alveoli ◦ Organisms colonise bronchi and spread to alveoli ◦ Affected areas consolidated locally –lobules and eventually whole lobes-confluent ◦ Young/elderly/immobile Distinction blurred -similarities in confluent bronchopneumonia Gross anatomy Clinical setting • Community acquired • Hospital acquired: Nosocomial • Immuno-compromised patient • Aspiration pneumonia • Necrotising pneumonia and lung abscess • Chronic pneumonia These sub-divisions are useful as each type of pneumonia is associated with a particular group of likely pathogens Community acquired pneumonia (CAP) • Streptococcus pneumoniae – most common cause • Haemophilus influenzae • Moraxella catarrhalis • Klebsiella pneumoniae • Pseudomonas aeruginosa • Legionella pneumophila • Viruses: influenza, metapneumovirus, COVID-19 Bacterial pneumonias are characterized by predominantly intra-alveolar neutrophilic inflammation, while viral pneumonia shows interstitial lymphocytic inflammation Hospital acquired: nosocomial • Pulmonary infection acquired in the course of a hospital stay • Underlying disease, immunosuppression, prolonged antibiotic therapy, invasive access device, mechanical ventilator • Serious, and often life threatening • Important cause of death or prolonged hospital stay • Staphylococcus aureus (gram positive cocci) • Enterobacteriacae & Pseudomonas species (gram negative rods) • Patients often have abnormal colonisation of upper respiratory tract with gram negative bacteria which colonise lower tract if immune resistance lowered Immuno-compromised Organ transplant patients/ cancer treatment/ existing disease Opportunistic infection (organisms that rarely cause disease in normal host) ◦ Bacteria: Mycobacterial infection ◦ Viruses: Cytomegalovirus (CMV), Herpes simplex ◦ Fungi: Pneumocystis jiroveci, Candida, Aspergillus + usual bacterial/viral/fungal organisms Aspiration pneumonia § Aspiration of gastric contents: ◦ ◦ ◦ ◦ Abnormal gag/swallow reflexes e.g. after a stroke, MS Unconsciousness Repeated vomiting Poor oral hygiene § Pneumonia is due to both irritation of gastric contents and bacteria § Anaerobic bacteria: oral flora § Aerobic: ◦ S pneumoniae, S aureus, H influenza, Pseudomonas aeruginosa § Often necrotising, frequent cause of death, abscess formation in survivors Necrotising pneumonia and lung abscess • Complication/progression of pneumonia • Inflammation and damage results in reduction of vascular supply to tissue – cell death • Access for antibiotics reduced – infection progresses • Frequently causes death • Survivors often have lung abscesses • Aspiration of infected material – most common cause • Can resolve with antimicrobial therapy leaving a scar Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • Describe the causative agents of chronic pneumonia Symptoms and treatment of acute bacterial pneumonia Symptoms: ◦ ◦ ◦ ◦ Fever, chills, dyspnoea Cough with or without sputum (purulent – bacterial, watery – viral) Crackles on auscultation Consolidation in radiograph Diagnosis: ◦ Sputum: Bacteria/virus. Gram staining, bacterial culture (suitable antibiotic) ◦ X-ray ◦ FBC Treatment: Antibiotic (empirically-can be changed on results) Possible outcomes of pneumonia • Resolution: destruction of connective tissue/vasculature minimal/absent. Neutrophils destroy organism, exudate liquified by neutrophil enzymes (fibrin breakdown /phagocytosis of dead cells), this is coughed up/reabsorbed by capillaries/drained in lymph. Epithelial stem cell proliferation and differentiation into type I and II pneumocytes • Organisation: scar tissue/fibrosis from destruction of connective tissue. Possible bronchiectasis. • Abscess formation • Empyema • Bacteremia (meningitis/arthritis/infective endocarditis) • Death Learning Objectives • Describe the pathological features of acute pneumonia • Describe the causative agents, routes of infection and classifications of acute pneumonia • Describe the clinical symptoms, treatment and possible outcomes of acute pneumonia • Describe the causative agents of chronic pneumonia Chronic pneumonia • Often a localised lesion in an immunocompromised patient • Typically a granulomatous inflammation • Caused by bacteria (e.g. Mycobacterium tuberculosis) or fungi § Histoplasma capsulatum – infection can occur in immunocompetent individuals § Blastomyces dermatitidis – soil-inhabiting fungus § Coccidiodies immitis – pyogenic, granulomatous or mixed

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