Introduction to Immune Defense Mechanisms
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Questions and Answers

What role does saliva play in the body's first line of defense against infections?

Saliva constantly flows and contains enzymes like peroxidase and lysozymes that help eliminate microbial threats.

Explain how ciliated cells in the respiratory tract contribute to defense mechanisms.

Ciliated cells are lined with mucus that traps microbial threats, facilitating their removal from the respiratory tract.

Identify two components of humoral immunity involved in the body's defense against pathogens.

Cytokines and antibodies are two key components of humoral immunity.

What is the significance of antimicrobial susceptibility testing (AST) in diagnosing respiratory tract infections?

<p>AST is crucial for determining the effectiveness of antibiotics against isolated pathogens, addressing the issue of antimicrobial resistance.</p> Signup and view all the answers

How do adenoids and tonsils contribute to the immune response?

<p>Adenoids and tonsils are lymphoid tissues that help trap pathogens and activate immune responses.</p> Signup and view all the answers

What is meant by fomites in the context of infection transmission?

<p>Fomites refer to inert surfaces that can harbor pathogens, acting as intermediates in the transmission of infections.</p> Signup and view all the answers

Describe the process involved in collect appropriate samples for culture in laboratory diagnosis.

<p>Collecting appropriate samples involves assessing clinical history and ensuring the specimen is suitable for culture.</p> Signup and view all the answers

What are polymorphonuclear leukocytes, and what is their purpose in the immune response?

<p>Polymorphonuclear leukocytes are a type of white blood cell that play a key role in the body's defense by engulfing and destroying pathogens.</p> Signup and view all the answers

What laboratory method can be used for analyzing sputum samples in respiratory infections?

<p>Sputum samples must be digested before analysis.</p> Signup and view all the answers

List two types of agar used in the culture conditions for respiratory tract infections.

<p>Selective and non-selective agars.</p> Signup and view all the answers

What are common symptoms associated with sinusitis?

<p>Fluid build-up in sinuses, runny and stuffy nose, facial pain, and headaches.</p> Signup and view all the answers

Why should invasive techniques be avoided in very sick patients?

<p>Invasive techniques can exacerbate the patient's condition.</p> Signup and view all the answers

What is a typical treatment approach for sinusitis?

<p>Self-care for pain relief, and occasionally steroid nasal sprays for severe cases.</p> Signup and view all the answers

Name a common bacterial upper respiratory tract infection.

<p>Pharyngitis/tonsillitis.</p> Signup and view all the answers

What complicates the interpretation of isolated organisms from respiratory samples?

<p>The interpretation can be complicated due to various growth requirements and the presence of multiple organisms.</p> Signup and view all the answers

What is the role of biochemical testing in identifying pathogens?

<p>Biochemical testing helps determine the metabolic capabilities of the isolated organism.</p> Signup and view all the answers

What are the signs and symptoms typically lasting up to 10 days during a respiratory tract infection?

<p>Runny and stuffy nose, sore throat, cough, and bad breath.</p> Signup and view all the answers

What are the common pathogens associated with sinusitis?

<p>Typically, viruses and sometimes bacteria.</p> Signup and view all the answers

What is the typical duration of symptoms for laryngitis?

<p>1-2 weeks</p> Signup and view all the answers

Identify one common viral cause of pharyngitis.

<p>Adenoviruses</p> Signup and view all the answers

What is a common bacterial cause of pharyngitis in children?

<p>Streptococcus pyogenes</p> Signup and view all the answers

What often causes blockage of the Eustachian tubes in otitis media?

<p>Fluid build-up</p> Signup and view all the answers

What type of bacterium is Streptococcus pyogenes classified as?

<p>Non-motile Gram-positive cocci</p> Signup and view all the answers

What is the first-line antibiotic for treating GAS pharyngitis?

<p>Penicillin</p> Signup and view all the answers

What symptom is common during laryngitis aside from hoarseness?

<p>Sore throat</p> Signup and view all the answers

What is the typical approach to treating otitis media?

<p>Self care and pain relief</p> Signup and view all the answers

How is Streptococcus pyogenes commonly stained in laboratory environments?

<p>Stained purple</p> Signup and view all the answers

In which cases are antibiotics rarely used for treating respiratory infections?

<p>Mild cases</p> Signup and view all the answers

What is the role of M protein types in relation to autoimmune responses?

<p>M protein types can be rheumatogenic, potentially leading to autoimmune conditions such as rheumatic carditis.</p> Signup and view all the answers

Explain the difference between Streptolysin O and Streptolysin S.

<p>Streptolysin O is oxygen liable and antigenic, while Streptolysin S is oxygen stable but not antigenic.</p> Signup and view all the answers

What is the function of Dnase produced by Streptococcus pyogenes?

<p>Dnase degrades DNA, facilitating the breakdown of neutrophil extracellular traps.</p> Signup and view all the answers

Describe the effect of opsonins on the phagocytic process.

<p>Opsonins enhance phagocytosis by marking pathogens for easier recognition and ingestion by phagocytes.</p> Signup and view all the answers

What condition is characterized by a ‘strawberry tongue’ and a rash starting on the trunk?

<p>Scarlet fever is characterized by a ‘strawberry tongue’ and a rash that typically begins on the trunk.</p> Signup and view all the answers

Who is most at risk for post pharyngitis complications from untreated infections?

<p>Children aged 5-15 years are most at risk for life-threatening post pharyngitis complications from untreated infections.</p> Signup and view all the answers

What role do pili and LTA play in bacterial infections?

<p>Pili and Lipoteichoic Acid (LTA) facilitate adherence of bacteria to host cells.</p> Signup and view all the answers

How does the hyaluronic acid capsule benefit Streptococcus pyogenes?

<p>The hyaluronic acid capsule helps the bacteria evade the host immune system by mimicking host tissue.</p> Signup and view all the answers

What are NETs and how does S.pyogenes's DNase affect them?

<p>NETs, or neutrophil extracellular traps, are structures that trap bacteria; S.pyogenes's DNase degrades these traps.</p> Signup and view all the answers

What is the significance of introducing penicillin in the treatment of streptococcal infections?

<p>The introduction of penicillin has significantly reduced the incidence of serious complications from streptococcal infections.</p> Signup and view all the answers

What is molecular mimicry and how does it relate to autoimmune responses in respiratory tract infections?

<p>Molecular mimicry is when foreign antigens are similar to self antigens, leading the immune system to confuse them and initiate an autoimmune response.</p> Signup and view all the answers

Describe the role of the M protein of S. pyogenes in the pathogenesis of rheumatic fever.

<p>The M protein of S. pyogenes mimics myosin found in heart valves, leading to an autoimmune attack on the heart and potentially causing rheumatic fever.</p> Signup and view all the answers

List at least two complications that can arise from a delayed antibody-mediated response following a GAS infection.

<p>Complications include myocarditis and Sydenham's chorea.</p> Signup and view all the answers

How do activated T cells contribute to the pathogenesis of rheumatic heart disease after a GAS infection?

<p>Activated T cells enter the lymphatic system and travel to affected areas, such as the heart, causing inflammation and subsequent damage.</p> Signup and view all the answers

What are subcutaneous nodules and erythema marginatum, and how do they relate to rheumatic fever?

<p>Subcutaneous nodules and erythema marginatum are skin manifestations of rheumatic fever, indicating systemic inflammation during immune response.</p> Signup and view all the answers

What is the significance of cross-reactive antibodies that can be generated in response to a GAS infection?

<p>Cross-reactive antibodies can target both bacterial and self antigens, resulting in immune-mediated damage to organs such as the heart.</p> Signup and view all the answers

Explain how inflammation of the heart muscle (myocarditis) can occur after a GAS infection.

<p>Myocarditis occurs when activated T and B cells infiltrate the heart tissue due to similar antigens presented by GAS and self proteins.</p> Signup and view all the answers

Flashcards

Physical Defenses

The first line of defense against infection. This includes physical barriers like skin and mucus membranes, as well as chemical defenses like saliva.

Saliva

A sticky substance that traps microbes and contains enzymes like lysozymes and peroxidase to kill them.

Hairs in Nasal Passages

Tiny hairs in the nose that act as a physical barrier to trap microbes.

Cough Reflex

A reflex action that expels foreign particles from the respiratory tract.

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Ciliated Cells

Cells with tiny hair-like structures that move in a rhythmic motion to propel mucus and trapped microbes out of the respiratory tract.

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Antibodies

A substance produced by the immune system that helps fight off infection.

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Alveolar Macrophages

White blood cells that engulf and destroy microbes.

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Antimicrobial Susceptibility Testing (AST)

The process of identifying and testing the susceptibility of a bacterial species to antimicrobial drugs.

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Pharyngitis/tonsillitis

A type of respiratory infection that affects the tonsils and the back of the throat.

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Rhinitis

Inflammation of the nasal cavity, often causing a runny or stuffy nose.

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Sinusitis

Infection of the sinuses, often causing facial pain, headaches, and a stuffy nose.

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Laryngitis

Inflammation of the larynx or voice box, causing hoarseness or loss of voice.

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Otitis media

Infection of the middle ear canal, causing pain and discomfort.

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BAL (Bronchoalveolar Lavage)

A sample taken from the lungs, using a bronchoscope to wash the airways, used to identify respiratory infections.

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Sputum sample

A type of sample that is collected from the lungs by coughing, used to identify respiratory infections.

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Selective agar

A culture medium that encourages the growth of specific types of bacteria.

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Non-selective agar

A culture medium that allows the growth of a wide variety of bacteria, but doesn't favor any specific type.

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Enrichment Broth

A liquid culture medium that promotes the growth of bacteria.

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Molecular Mimicry

A condition where the body's immune system mistakenly attacks its own tissues due to similarities between foreign and self-antigens. This can occur when antibodies or T cells developed to fight a foreign antigen (like Streptococcus pyogenes M protein) also react with similar components found in the body (like myosin in heart valves).

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What is Laryngitis?

An infection of the larynx (voice box) that causes inflammation and irritation.

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What is a common symptom of Laryngitis?

It causes the voice to become hoarse or croaky, and may even lead to a complete loss of voice.

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Myocarditis

Inflammation of the heart muscle, a possible complication of rheumatic fever.

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Sydenham's Chorea

A neurological disorder causing uncontrolled, jerky movements, a complication of rheumatic fever.

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What causes the symptoms of Laryngitis?

Swollen and irritated tissues in the larynx.

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Rheumatic Fever

A multi-system inflammatory disorder affecting the heart, joints, and skin. It can be a complication of Streptococcus pyogenes infection.

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What is Pharyngitis?

A bacterial infection that causes inflammation of the pharynx (throat).

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What is Otitis Media?

Infection of the middle ear, often caused by a buildup of fluid in the ear.

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Subcutaneous Nodules

Nodules that form under the skin, a possible complication of rheumatic fever.

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Erythema Marginatum

A rash with a red, ring-shaped appearance, a possible complication of rheumatic fever.

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What is a common symptom of Otitis Media?

A common symptom of Otitis Media in adults.

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What is a key characteristic of Streptococcus pyogenes?

It's a non-motile, Gram-positive bacteria that comes in chains.

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Pharyngitis → Rheumatic Heart Disease

A sequence of events that begins with a Streptococcus pyogenes infection (pharyngitis) and can lead to rheumatic heart disease.

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What is Streptococcus pyogenes known for?

This type of bacteria is known for causing sore throats and other infections.

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What type of antibiotics are often used to treat pharyngitis?

They're often used to treat pharyngitis caused by Streptococcus pyogenes.

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What distinguishes Streptococcus pyogenes under a microscope?

It stains purple under a microscope due to its thick peptidoglycan layer.

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M protein

A type of protein produced by Streptococcus pyogenes that can trigger autoimmune reactions, especially in individuals with a genetic predisposition. These proteins are crucial for the bacterium's virulence, as they help it evade the host's immune system. They can cause inflammation of the heart, joints, and skin, leading to complications like rheumatic carditis.

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Streptokinase

An enzyme produced by Streptococcus pyogenes that breaks down fibrin, a protein involved in blood clotting. This action helps the bacteria spread by dissolving blood clots and preventing them from being trapped.

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Opsonin

A molecule that binds to a pathogen and enhances its recognition by phagocytic cells (like macrophages) for engulfment and destruction, thereby aiding the immune response.

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NET (Neutrophil Extracellular Trap)

A component of the host's immune defense system; They are structures released by neutrophils (type of immune cell) to trap bacteria. These webs are made of DNA, which can be broken down by DNase produced by Streptococcus pyogenes.

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DNase

A virulence factor produced by Streptococcus pyogenes that degrades DNA released by neutrophils during the formation of NETs (Neutrophil Extracellular Traps). This helps the bacteria evade the immune trap and spread further in the body.

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Scarlet Fever

A serious complication of Streptococcus pyogenes infection that presents with a characteristic red rash spreading from the trunk to the extremities, and a red, inflamed tongue, often called 'strawberry tongue'.

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Streptolysin O

A type of extracellular enzyme produced by Streptococcus pyogenes that breaks down red and white blood cells. It is responsible for the characteristic beta hemolysis on agar plates. It is also antigenic, meaning it can trigger an immune response.

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Pili (Fimbriae)

A virulence factor produced by Streptococcus pyogenes that helps establish the bacteria on the surface of host cells by mediating their adherence. The cells bind to the host's cells through a process called adherence.

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SpyCEP

A surface-expressed protease produced by Streptococcus pyogenes that interferes with the immune response by cleaving a vital signaling molecule, IL-8, which attracts neutrophils to the site of infection. This allows the bacteria to evade the immune response.

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Streptolysin S

An extracellular enzyme produced by Streptococcus pyogenes that is stable in the presence of oxygen. It is responsible for the beta hemolytic appearance on agar plates but, unlike Streptolysin O, does not trigger an immune response.

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Study Notes

Respiratory Tract Infections

  • Respiratory pathogen transmission and host defense mechanisms are key learning outcomes.
  • Infections of the upper and lower respiratory tract, as well as those affecting the immunocompromised and those with COPD, are covered.
  • Post-identification processes and antimicrobial susceptibility testing (AST) are also learning outcomes.

Pathogens of the Upper and Lower Respiratory Tract

  • Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae are among the bacteria causing respiratory tract infections.
  • Viral pathogens like Influenza, Parainfluenza, Adenovirus, Rhinovirus, and Respiratory syncytial virus also cause infections.
  • Fungal pathogens such as Aspergillus spp., Cryptococcus neoformans/gattii, Histoplasma capsulatum, and Paracoccidioides brasiliensis can also cause respiratory illness.

Host Defense Mechanisms

  • Humans inhale an average of 500,000 organisms daily.
  • Physical defenses like saliva (enzymes like peroxidase, lysozyme, lactoferrin), hairs in the nose, and the cough reflex are essential.
  • Cilia in the respiratory tract trap microbes, preventing further infection.

Laboratory Diagnosis

  • A thorough clinical history and suitable specimen collection are essential.
  • Appropriate sample types for culture include sputum, swabs, biopsies, and blood.
  • Microscopic, culture, and quantitative analyses are employed, along with biochemical tests.
  • Serologic, genetic, and antimicrobial susceptibility testing (AST) all help to identify pathogens.

Infections of the Upper Respiratory Tract (URTI)

  • Infections like sinusitis, pharyngitis, tonsillitis, rhinitis, laryngitis, and otitis media are prevalent and have unique symptoms.

Infections of the Lower Respiratory Tract

  • Pneumonia, caused by a variety of pathogens, is a major concern.
  • Pneumonia can be classified into different subtypes, including community-acquired and hospital-acquired pneumonia.

Post-Pharyngitis Complications

  • Scarlet fever often accompanies pharyngitis.
  • The rash initially appears on the trunk and spreads to extremities.
  • Untreated pharyngitis can lead to serious complications.

Infections of the Compromised Host

  • Individuals with conditions like organ transplantation, cystic fibrosis, COPD, diabetes, and HIV are at higher risk.

Important Pathogens

  • Haemophilus influenzae is a common cause of respiratory tract infections, particularly in the upper respiratory tract.
  • Moraxella catarrhalis is another common respiratory pathogen, usually in the upper respiratory tract.

Antimicrobial Susceptibility Testing (AST)

  • Antimicrobial resistance testing is crucial due to the possibility of microbes becoming resistant.
  • Different methods to identify antimicrobial resistance in microbes are used like disc diffusion, E-TEST, and broth dilution.

Diagnostic Methods and Technologies

  • Vitek 2 is a rapid diagnostic technology aiding susceptibility testing and microbial identification by using colorimetric cards and growth-based technology.
  • Next-generation sequencing (NGS) can be used in identifying bacterial pathogens from patients' samples.

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Related Documents

Respiratory Tract Infections PDF Lecture Notes

Description

This quiz explores the various components and mechanisms of the immune system, focusing on the body's first line of defense against infections. It covers topics such as saliva's role, ciliated cells, humoral immunity, and the significance of antimicrobial susceptibility testing. Test your understanding of how different elements contribute to immune responses and infection control.

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