Introduction to Immune Defense Mechanisms

Podcast

Play an AI-generated podcast conversation about this lesson

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?

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

How do adenoids and tonsils contribute to the immune response?

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

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

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

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

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

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

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

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

Sputum samples must be digested before analysis. Signup and view all the answers

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

Selective and non-selective agars. Signup and view all the answers

What are common symptoms associated with sinusitis?

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

Why should invasive techniques be avoided in very sick patients?

Invasive techniques can exacerbate the patient's condition. Signup and view all the answers

What is a typical treatment approach for sinusitis?

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

Name a common bacterial upper respiratory tract infection.

Pharyngitis/tonsillitis. Signup and view all the answers

What complicates the interpretation of isolated organisms from respiratory samples?

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

What is the role of biochemical testing in identifying pathogens?

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

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

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

What are the common pathogens associated with sinusitis?

Typically, viruses and sometimes bacteria. Signup and view all the answers

What is the typical duration of symptoms for laryngitis?

1-2 weeks Signup and view all the answers

Identify one common viral cause of pharyngitis.

Adenoviruses Signup and view all the answers

What is a common bacterial cause of pharyngitis in children?

Streptococcus pyogenes Signup and view all the answers

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

Fluid build-up Signup and view all the answers

What type of bacterium is Streptococcus pyogenes classified as?

Non-motile Gram-positive cocci Signup and view all the answers

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

Penicillin Signup and view all the answers

What symptom is common during laryngitis aside from hoarseness?

Sore throat Signup and view all the answers

What is the typical approach to treating otitis media?

Self care and pain relief Signup and view all the answers

How is Streptococcus pyogenes commonly stained in laboratory environments?

Stained purple Signup and view all the answers

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

Mild cases Signup and view all the answers

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

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

Explain the difference between Streptolysin O and Streptolysin S.

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

What is the function of Dnase produced by Streptococcus pyogenes?

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

Describe the effect of opsonins on the phagocytic process.

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

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

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

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

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

What role do pili and LTA play in bacterial infections?

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

How does the hyaluronic acid capsule benefit Streptococcus pyogenes?

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

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

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

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

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

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

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

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

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. Signup and view all the answers

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

Complications include myocarditis and Sydenham's chorea. Signup and view all the answers

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

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

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

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

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

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

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

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

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.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

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.