WEEK 1: Acute Respiratory Infections and pneumonias Flashcards
(30 cards)
Outline the 4 Upper airway defenses.
- Nasal hairs -trap large air particles,
- Ciliated epithelium clear smaller particles
- Cough reflex -expectoration,
- Larynx –sphincter -closes to protect the airway during swallowing and vomiting
The sterility, structure and function of the lower airways are maintained by the innate and adaptive immune responses.
Outline the Lower airway defenses.
- Airway mucus; antimicrobial peptides (such as defensins, IgA and lysozyme), anti-proteinases and antioxidants
- opsonization and killing of bacteria and the regulation of the proteolytic enzymes secreted by inflammatory cells
- Muco-ciliary escalator
- Macrophages engulf microbes, organic dusts and other particulate matter.
- Pulmonary circulation contains a marginated pool of neutrophils -recruited in response to bacterial infection.
- Adaptive immunity is characterized by the specificity of the response and the development of memory.
Define OPPORTUNISTIC PATHOGENS.
Usually benign but have the ability to cause disease in an immunocompromised host (e.g., patients with AIDS, chemotherapy)
Outline examples of opportunistic pathogens.
Examples ofopportunistic infectionsinclude:
-Oral candidiasis
-Pneumocystis Jirovecci Pneumonia
-Cytomegalovirus
-Cryptococcal Meningitis
Define COMMENSAL MICROORGANISMS
Microorganisms (e.g., bacteria, fungi) living on or within humans that do not harm the host under normal circumstances and may even be beneficial (e.g., by inhibiting the growth of pathogens or helping with digestion)
Give examples of commensal microorganisms and where they are found.
Examples;
Normal nasal flora:Staphylococcus epidermidis
Normal oropharyngeal flora:Viridans group streptococci
Normal lung flora:Neisseriacatarrhalis,alpha-hemolyticstreptococci,staphylococci, non-pathogeniccorynebacteria,Candida albicans, Bacteroides, haemophilus influenzae
Normal flora ofdental plaques:Streptococcus mutans
Normal gut flora:Escherichia coliandBacteroides
Define LOWER RESPIRATORY TRACT INFECTIONS (LRTI) and give examples.
Infections (usually bacterial or viral) involving the lower respiratory tract, which may affect the bronchi, lung parenchyma, or both.
Examples include pneumonia, bronchitis, lung abscess.
What is bronchitis?
State its main cause.
State 6 signs and symptoms.
Outline differential diagnoses.
Describe thew management.
Outline complications that may come about.
Inflammationof the bronchi
Often follows an upper respiratory tract infection (URTI) and, in >90% of cases, the cause is viral.
May manifest with cough, dyspnea, chest pain, runny nose, headache, and malaise.
**The cough is often productive and may persist for2–3 weeksand is usually self-limiting.
Clinical diagnosis; clinical symptoms and auscultationfindings (Clear or wheeze)
Further diagnostic testing is not routinely necessary.
Differential diagnoses; asthma, acute exacerbation of COPD, and pneumonia
Management consists of adequate hydration and symptomatic relief.
Treatment with antibiotics generally not indicated.
Complications include Respiratory Failure, Secondary bacterial infections (especially pneumonia)
Define pneumonia.
How is it transmitted?
State the most common bacterial pathogens.
Describe the classification of pneumonia.
Inflammationof the alveolar space and/or the interstitial tissue of the lungs.
Transmission: aspirationof airborne pathogens (mainly bacteria, but also virusesand fungi)
The most common bacterial pathogens include Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus.
Causative pathogens can be inferred based on patient age, immune status and where the infection was acquired. Definitively identified on sputum/blood culture
Classified based on clinical features as either typical or atypical.
Compare typical vs atypical pneumonia.
Typical Pneumonia:
- Bacterial Infections:
Most cases of typical pneumonia are caused by bacteria.
The most common bacterial pathogens include Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus. - Abrupt Onset: Typical pneumonia often has a sudden and more severe onset of symptoms.
- This includes a high fever, chills, productive cough with discolored sputum, chest pain, and difficulty breathing.
- Consolidation of Lung Tissue: Bacterial pneumonia typically leads to consolidation of lung tissue, meaning that the alveoli are filled with inflammatory cells and fluid, reducing the lung’s ability to exchange oxygen and carbon dioxide.
- Response to Antibiotics: Treatment for typical bacterial pneumonia involves antibiotics. The choice of antibiotic depends on the specific bacteria causing the infection.
Atypical Pneumonia:
- Various Pathogens:
Atypical pneumonia is caused by pathogens such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila.
These are often intracellular bacteria a
and do not respond as well to traditional antibiotics.
- Gradual Onset: Symptoms of atypical pneumonia tend to develop more gradually and are often less severe compared to typical pneumonia.
- Common symptoms include a persistent dry cough, headache, fatigue, and sometimes gastrointestinal symptoms.
- Patchy Infiltrates in Lungs: Unlike the consolidated appearance seen in typical pneumonia, atypical pneumonia often leads to more diffuse and patchy infiltrates in the lungs.
- Macrolide or Tetracycline Treatment: Atypical pneumonia is often treated with macrolide antibiotics (such as azithromycin) or tetracyclines (such as doxycycline).
Describe the diagnosis and treatment of pneumonia.
Diagnostics include blood tests for inflammatory markers,radiographic imaging and pathogen detection in blood, urine, or sputum samples.
Inflammatory markers: C-reactive protein, Procalcitonin, ESR
Management consists of empiric antibiotic treatmentand supportive measures (e.g., oxygen administration,IV Fluids).
Outline PNEUMONIA: RISK FACTORS.
- Immunosuppression: HIV, Chemotherapy, malnutrition, diabetes, alcoholism
- Chronic diseases: Pre-existing cardiopulmonary diseases, acquired or congenital lung abnormalities.
- Impaired airway protection: Smoking, altered consciousness
- Environmental factors: Toxins, crowded living arrangement, endemic areas, zoonotic exposures, contaminated water systems.
- Surgical procedures: Chest surgery, Upper abdominal surgery
Outline the routes of infection for pneumonia.
Routes of infection
Most common:micro-aspiration(droplet infection) ofairborne pathogensor oropharyngeal secretions
Aspirationofgastric acid(aspiration pneumonitis), food, or liquids
Hematogenous dissemination (uncommon)
Describe the pathogenesis of pneumonia.
Pathogenesis
1. Failure of protective pulmonary mechanisms(e.g.,cough reflex,mucociliary clearance,alveolar macrophages)
- Infiltration of thepulmonary parenchymaby thepathogen→interstitialand alveolar inflammation.
- Impairedalveolar ventilation→ventilation/perfusion(V/Q) mismatchwith intrapulmonary shunting (right to left)
- Hypoxiadue to increasedalveolar-arterial oxygen gradient
DESCRIBE PNEUMONIA CLASSIFICATION BY LOCATION ACQUIRED.
Define community acquired pneumonia and outline the causative pathogens.
Describe Hospital acquired pneumonia and outline the causative pathogens.
Describe Ventilator associated pneumoniae.
Develops in the outpatient setting or within 48 hours of admission into the hospital.
Develops at least 48 hours after admission into the hospital.
-Streptococcus aureus, Staphylococcus pneumonia, Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter spp
-Characterized by increased exposure to Multi drug resistant organisms.
Healthcare-associated pneumonia(HCAP): pneumonia acquired inhealthcare facilities(e.g., hospital, nursing homes, thehemodialysiscenters, and outpatient clinics); this terminology is no longer recommended but is included for historical purposes.
Develops more than 48 hours after endotracheal intubation or within 48 hours of extubating.
Describe the 4 pneumonias according to Area of lung affected by the pathology.
Lobar pneumonia: pneumonia affecting one lobe of a lung.
Bronchial pneumonia: pneumonia affecting the tissue around the bronchi and/or bronchioles.
Interstitial pneumonia: pneumonia affecting the tissue between the alveoli.
Cryptogenic organizing pneumonia (formerly known as bronchiolitis obliterans organizing pneumonia): a noninfectious pneumonia of unknown etiology characterized by the involvement of the bronchioles, alveoli, and surrounding tissue.
PNEUMONIA: PATHOLOGICAL CLASSIFICATION.
- -Radiological and pathological term referring to a Classical/Typical type of Pneumonia, characterized by homogeneous consolidation of one or more lung lobes, often with associated pleural inflammation.
-Characterized by inflammatoryintra-alveolarexudate, resulting in consolidation
Infection spreads to adjacent alveoli until constrained by anatomical barriers between segment or lobes of the lungs.
- *Refers to more patchy alveolar consolidation associated with bronchial and bronchiolar inflammation
*Characterized by inflammatory infiltrates that fill thebronchiolesand the adjacentalveoli(patchy distribution)
*Usually involves the lower lobes or right middle lobe and affects≥ 1 lobe
*Necrotizing bronchopneumoniaandpneumatocelecan be caused byStaphylococcus aureusand are often preceded by aninfluenzainfection
Name the 2 described above.
- Lobar pneumonia
- Broncho pneumonia
Describe miliary pneumonia and cryptogenic organizing pneumonia.
*Miliary pneumonia: multiple small infiltrations caused by hematogenous dissemination (e.g., oftuberculosis)
*Cryptogenic organizing pneumonia: characterized byinflammationof thebronchiolesand surrounding structures
Describe Interstitial pneumonia.
*Characterized by a diffuse patchyinflammationthat mainly involves the alveolarinterstitialcells
*Bilateral multifocal opacities are classically found onchest x-ray
*Often has an indolent course (walking pneumonia)
Lobar pneumonia is a specific form of pneumonia characterized by the involvement of an entire lobe of one lung.
The progression of lobar pneumonia typically goes through four stages, known as the four classic stages of pneumonia.
Describe the 4 stages of lobar pneumonia.
These stages were first described by Sir William Osler. Here’s an overview of each stage:
- Congestion (Stage 1):
Timeframe: 0-2 days after infection.
Pathological Changes: The affected lobe becomes congested with blood and the blood vessels dilate.
The alveoli start to fill with a serous fluid, white blood cells, and bacteria. This initial stage is characterized by vascular engorgement and edema.
Clinical Features: Patients may experience non-specific symptoms such as fever, malaise, and cough. Chest pain may be present.
- Red Hepatization (Stage 2):
Timeframe: 3-4 days after infection.
Pathological Changes: The lung becomes more solid as the red and white blood cells, bacteria, and fibrin accumulate in the alveoli. This gives the affected lobe a liver-like (hepatized) appearance.
Clinical Features: Symptoms intensify, with high fever, productive cough (often with rust-colored sputum), increased chest pain, and signs of consolidation on physical examination, such as dullness to percussion and bronchial breath sounds.
- Gray Hepatization (Stage 3)
Timeframe: 5-7 days after infection.
Pathological Changes: The red blood cells in the affected area undergo degeneration, resulting in a grayish appearance of the hepatized tissue.
The inflammatory exudate begins to break down.
Clinical Features: Fever may start to subside, and there may be a gradual resolution of symptoms.
However, cough and weakness may persist.
- Resolution (Stage 4):
Timeframe: Beyond 8 days after infection.
Pathological Changes: The inflammatory exudate is further broken down and cleared by macrophages.
The lung tissue gradually returns to normal, and the alveoli are restored to their normal state.
Clinical Features: Symptoms continue to improve, and the patient starts to recover. Resolution may take weeks, and complete recovery may require a longer period.
Outline the causative agents for pneumonia in immunocompromised patients.
-Pneumocystis jirovecii pneumoniae
-Aspergillus fumigatus
-Histoplasma capsulatum
-Candida species
-CMV
-s.aureus
Outline some causes of lobar consolidation.
-Lobar pneumonia
-Neoplasm
-Hemorrhage: contusion, infarction
State the 2 main causative agents of pneumonia across all age groups.
- Staphylococcus pneumoniae
- Hemophilus influenza
Compare the presentations of typical and atypical pneumonia.
Typical pneumonia; sudden onsetmalaise,fever, and a productivecough. Onauscultation,cracklesand bronchial breath sounds are audible.
-Characterized by asudden onset of symptoms caused by lobar infiltration.
-Productive cough with purulent sputum (yellow greenish)
-Fever, chills, malaise, Pleuritic chest pain
Clinical Signs
-Signs of consolidation (e.g., ↑ tactile fremitus, —
Dullness to percussion,↑ egophony, bronchialbreath sounds onauscultation)
Abnormal Auscultation (Egophony): In cases of lung consolidation, where there is a solidification of lung tissue (as seen in pneumonia), the sound transmission may be altered.
Instead of hearing the expected “E” sound, the examiner may hear a nasal or bleating quality, resembling the sound of a goat. This altered sound is termed “egophony.”
-Signs of infiltrates; crackles on auscultation
-Tachypnea andrespiratory distress
ATYPICAL PNEUMONIA
Atypical pneumonia; gradual onset unproductivecough,dyspnea, and extrapulmonary manifestations.
*Auscultationis usually unremarkable.
*Has anindolent course (slow onset), with less distinct classical symptoms (dry cough) and commonly manifests with extrapulmonary symptoms (fatigue, headaches, sore throat,myalgias, andmalaise)
often unremarkable findings onauscultationand percussion
