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Questions and Answers
What type of molecule is an antitoxin?
Antitoxin treatment provides active immunity.
False
What is the causative agent of walking pneumonia?
Mycoplasma pneumoniae
Latent tuberculosis is ______ and is not contagious.
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Match the tuberculosis tests with their function:
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What symptoms are associated with active tuberculosis?
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What is the best test for diagnosing walking pneumonia?
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Active tuberculosis is highly communicable and transmitted through contact.
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What contributes to children being more prone to otitis media?
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Sequelae refers to the state of an organism after successful treatment of a disease.
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What is the Lancefield group for Streptococcus pyogenes?
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An _______ is a foreign substance that can bind to a receptor and trigger an immune response.
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Match the terms with their definitions:
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What is a mechanism for the rise in macrolide resistance in GAS?
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Diphtheria treatment involves using antitoxin to neutralize the diphtheria toxin.
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What are the common specimens collected from the lower respiratory tract (LRT)?
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Which term describes a collection of pus in the body?
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What is the primary mechanism by which Nystatin and Amphotericin B exert their antifungal effects?
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Necrotizing fasciitis is a commonly occurring infection associated with surgical wounds.
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What is the main feature of folliculitis?
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Immunological methods for diagnosing infectious diseases have higher sensitivity and specificity than culture methods.
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The coagulase-positive Staphylococcus is typically associated with __________.
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What is one example of a nucleic acid method used for diagnosing infectious diseases?
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Match the skin infections with their descriptions:
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The type of vaccine recommended for adults over 60 against RSV should be given in late __________ to early __________.
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Which laboratory test is typically recommended if a fungal infection is suspected?
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Match the groups with their recommended RSV immunization strategies:
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What is a disadvantage of using immunological methods for diagnosing infectious disease?
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The presence of coagulase-negative Staphylococcus indicates a highly pathogenic infection.
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What is the primary action of azoles in antifungal treatment?
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Sequelae are conditions that arise as a consequence of a previous disease.
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Name two sequelae of bacterial pharyngitis.
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What type of pathogens are characterized by thermal dimorphism and can cause infections in healthy individuals?
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Ubiquitous fungal pathogens are generally considered true pathogens capable of infecting healthy individuals.
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What is the function of sebum in skin protection?
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The _______ is a vascular rash that appears all over the body as a result of VZV infection.
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Match the following terms related to the skin infections:
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What is a key reason why latency is more common among DNA viruses compared to RNA viruses?
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Lysozyme is an enzyme found in sweat that helps to break down lipids on the skin.
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What effect do nucleoside analog drugs have on viral replication?
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Study Notes
Otitis Media
- Children are more prone to developing otitis media due to shorter eustachian tubes, which allows less drainage of fluid in the middle ear and favors bacterial infection.
Superantigens
- Superantigens act as virulence factors by targeting T helper cells, leading to non-specific activation and overstimulation of the immune system.
- This causes massive inflammation, harmful to the host, and is often pyrogenic (fever-inducing).
Sequelae of GAS Bacterial Pharyngitis
- Sequelae are conditions that follow a previous disease or injury.
- GAS bacterial pharyngitis can lead to scarlet fever, rheumatic fever, heart disease, and acute glomerulonephritis (AGN), making prompt treatment essential.
Lancefield Classification System
- This system classifies Streptococcus species based on their reaction with specific antibodies.
- Group A strep (Streptococcus pyogenes) reacts with "A" antibody.
- Group B strep (Streptococcus agalactiae) reacts with "B" antibody.
- Streptococcus pneumoniae does not react with these antibodies.
Macrolide Resistance in GAS
- Macrolide resistance in GAS arises through acquiring erythromycin resistance via horizontal gene transfer.
- One mechanism involves a new gene coding for a macrolide efflux pump, which expels macrolide drugs from the cell.
Antigens, Antibodies, Antitoxins, and Toxoids
- Antigen: A foreign substance that can bind to a receptor and trigger an immune response.
- Antibody: A protein produced by the immune system to destroy foreign substances.
- Antitoxin: A solution of antibodies specifically designed to neutralize a particular toxin.
- Toxoid: A toxin that has been modified to no longer be pathogenic.
Antitoxin Production and Diphtheria treatment
- Antitoxins are produced by combining antibodies.
- They can treat diphtheria by neutralizing the diphtheria toxin from the vaccine antitoxin solution of antibodies.
Ubiquitous vs. Endemic Fungal Pathogens
- Ubiquitous fungal pathogens: Grow in various environments and are opportunistic pathogens, affecting immunocompromised individuals (e.g., Aspergillus).
- Endemic fungal pathogens: Found in specific geographical areas. They are characterized by thermal dimorphism and can cause infections in healthy individuals (e.g., Valley Fever).
Innate Factors Limiting Skin Infection
- Melanin: Has antimicrobial properties.
- Perspiration: Acidic pH and high salt concentration, washes away microbes.
- Lysozyme: An enzyme in sweat that breaks down peptidoglycan.
- Sebum: An oily substance produced by sebaceous glands; contains low pH lipids and proteins that moisturize.
- Skin microbiome: Acts as a barrier against pathogens.
Skin Lesion Terminology
- Lesion: Any change in tissue structure.
- Rash: A widespread eruption of lesions on the skin.
- Exanthem: A rash that is usually widespread and associated with a systemic disease.
- Vesicle/vesicular rash: A fluid-filled blister; a rash composed of vesicles.
- Macule: A flat, discolored lesion.
- Papule: A small, solid, raised lesion.
- Maculopapular rash: A rash with both macules and papules.
- Purpura: A purplish discoloration caused by bleeding under the skin.
- Petechiae: Small, pinpoint-sized purpuric lesions.
- Ulcer: An open sore that extends into the dermis or subcutaneous tissue.
Primary Infection vs. Reactivation of VZV and HSV1
- VZV: Primary infection (chickenpox) presents as a vascular rash all over the body. Reactivation (shingles) appears as a band of rash along the nerve where the virus resided.
- HSV1: Primary infection (oral herpes) can lead to recurring outbreaks in the same area.
Viral Latency
- Viral latency describes a dormant state of the virus within the host cell, where it is not actively replicating.
- Latency is more prevalent in DNA viruses as they can integrate into the host cell's genome, allowing for stable persistence and controlled gene expression during latency. RNA viruses, on the other hand, rely on rapid replication cycles.
Nucleoside Analog Drugs
- Nucleoside analog drugs inhibit viral replication by mimicking normal nucleotides.
- Acyclovir effectively treats VZV and HSV1 but cannot cure them because it is ineffective during the latency phase when the drugs cannot reach the virus.
Abscess, Cellulitis & Other Skin Infections
- Abscess: A collection of pus that can form in various body sites.
- Folliculitis: An infected hair follicle.
- Furuncle: A small abscess located deep in the hair follicle.
- Carbuncle: Multiple connected furuncles.
- Cellulitis: Infection of the lower dermis and subcutaneous fat, characterized by painful, swollen, reddened skin.
- Impetigo: Superficial pus-filled vesicles that crust over into honey-colored lesions.
- Erysipelas: Affects the dermis and superficial lymphatics. It presents with a red, painful appearance, and raised, well-defined borders. Can be a progression from impetigo.
- Necrosis: Tissue death due to loss of blood flow.
- Necrotizing fasciitis: A rare infection with rapid tissue destruction ("flesh-eating bacteria").
- Gangrene: Specific necrosis in an extremity, often foul-smelling.
Laboratory Tests for Skin Infections
- Routine culture and smear: Takes 2-3 days and is standard for tissue swabs and fluids.
- Anaerobic culture and smear: Takes 7 days and is used for closed wounds and abscesses.
- Fungal culture and smear: Takes 2-4 weeks and is used when fungal infection is suspected.
- Acid-fast culture and smear: Takes 2-8 weeks and is used when Mycobacterium infection is suspected.
Differentiating Staphylococcus and Streptococcus
- Catalase test: Staphylococcus is positive (+) and Streptococcus is negative (-) for catalase.
Coagulase-Positive Staphylococcus (CoPS) and Coagulase-Negative Staphylococcus (CoNS)
- CoPS: Usually Staphylococcus aureus and is highly pathogenic.
- CoNS: Less virulent but can cause infections in immunocompromised patients.
Antifungal Drug Mode of Action
- Azoles: Inhibit enzymes required for ergosterol synthesis in fungal cells.
- Nystatin and Amphotericin B: Bind to ergosterol in the fungal cell membrane, disrupting its integrity and leading to cell lysis.
Immunological Methods for Diagnosing Infectious Diseases
- Principle: Employ laboratory techniques involving antigens and specific antibodies.
- TAT (Turnaround Time): Minutes to a few hours.
- Advantages: Fast and easy to use.
- Disadvantages: Lower sensitivity and specificity compared to culture.
- Example: ELISA Test
Nucleic Acid Methods for Diagnosing Infectious Diseases
- Principle: Detect or amplify nucleic acids (DNA or RNA).
- TAT: 30 minutes to a few hours.
- Advantages: Very sensitive and specific.
- Disadvantages: Expensive.
- Example: PCR (Polymerase Chain Reaction)
RSV Immunization Strategies
- People over 60 years old: Receive RSV vaccine in late summer to early fall.
- Pregnant people: Receive RSV antibodies (Palivizumab) during pregnancy, typically between 32-36 weeks, from September to January.
- Newborns: Receive RSV antibodies if mothers were not vaccinated during pregnancy. Administered from October to March.
Superantigens and Sequelae in Bacterial Pharyngitis
- Superantigen: Causes the immune system to overreact, releasing many cytokines and activating T helper cells. GAS bacterial pharyngitis can have an erythrogenic toxin, which is a superantigen that triggers inflammation and dilation of the skin, leading to skin rash.
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Sequelae: Potential sequelae of bacterial pharyngitis include:
- Scarlet fever: Characterized by a red, sandpaper-like rash.
- Rheumatic fever: Triggers immune system attacks on the heart, skin, joints, and the nervous system.
Antitoxin: Production, Function and Diphtheria Treatment
- Antitoxin: A protein antibody used to neutralize toxins.
- Production: Produced by injecting a toxoid into horses and collecting the resulting antibodies from their blood.
- Diphtheria Treatment: Diphtheria antitoxin neutralizes the diphtheria toxin.
- Immunity Type: Antitoxin provides passive immunity.
Latent Tuberculosis Infection (LTBI) and Active Tuberculosis
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LTBI: The bacteria does not progress, the individual remains asymptomatic and the infection is not contagious. It can persist for years.
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Diagnostic Tests:
- Tuberculin skin test (TST): Intradermal injection of tuberculin, tested 48-72 hours later.
- Interferon-gamma release assay (IGRA): Blood test that detects immune response to tuberculosis antigens.
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Diagnostic Tests:
-
Active Tuberculosis: The bacteria is active, causing symptoms and being highly contagious via airborne transmission.
- Symptoms: Cough, blood sputum, weight loss, fatigue, night sweats, and chest pain.
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Diagnostic Test:
- Chest X-ray: Can be used to diagnose active tuberculosis.
Walking Pneumonia
- Diagnosis: Mycoplasma pneumoniae infection.
- Causative Agent: Mycoplasma pneumoniae.
- Best Diagnostic Test: Serology or NAAT (nucleic acid amplification test).
- Routine Bacterial Culture Results: Mycoplasma pneumoniae is slow-growing, making it unlikely to be successfully cultured using routine bacterial cultures, particularly as atypical pneumonia is often negative for bacterial cultures.
Shingles
- Diagnosis: Reactivation of varicella-zoster virus (VZV) or herpes zoster.
- Causative Agent: Varicella-zoster virus (VZV).
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Description
Test your knowledge on otitis media, superantigens, sequelae of GAS bacterial pharyngitis, and the Lancefield classification system in this microbiology quiz. Understand the implications of these conditions and their classification in medical microbiology.
