Study_guide_Exam_3

Exam 3 - Study Guide (Chapters 15-16, 17, 18, and 21)

This study guide provides key topics and details to facilitate your review for the exam. Refer to PowerPoints, book chapters, and lecture notes for comprehensive understanding.

Chapters 15 & 16 - Microbial Mechanisms of Pathogenicity; Disease and Epidemiology

Chapter 15

• Terminology

  • Signs vs. Symptoms:

    • Signs: Objective evidence of disease, measurable or observable (e.g., fever, rash).

    • Symptoms: Subjective experiences reported by victims (e.g., pain, fatigue).

  • Nomenclature of Symptoms: Familiarize with common medical terms used to describe symptoms.

• Classification of Diseases:

  • Infectious (caused by pathogens) vs Non-infectious (e.g., genetic, environmental).

  • Acute Diseases: Rapid onset, short duration (e.g., influenza).

  • Chronic Diseases: Long-lasting existence, may be controlled but not cured (e.g., diabetes).

  • Latent Diseases: Dormant stages that can re-emerge (e.g., herpes simplex).

• Periods of Disease Progression:

  • Incubation Period: Time from exposure to symptomatic stage.

  • Prodromal Period: Onset of vague symptoms.

  • Illness Period: Peak of disease.

  • Decline Period: Symptoms begin to subside.

  • Convalescence Period: Recovery and restoration of health.

• Duration of Diseases:

  • Acute: Symptoms appear suddenly and are short-lived (�3 days to weeks).

  • Chronic: Persist for months or years.

  • Latent: Inactive state with potential to reactivate.

• Normal Human Flora:

  • Transient Flora: Microbes that are temporary residents (e.g., from the environment).

  • Resident Flora: Normal microbes that are permanent residents, benefit the host in various ways (e.g., competition with pathogens).

  • Sterile Anatomical Sites: Body parts usually free of microbes (e.g., bloodstream, organs).

  • Consequences of Disruption: Could lead to infections like Clostridium difficile after antibiotic use.

• Major Factors in Developing Infections and Diseases:

  • Pathogens: Microorganisms causing disease (bacteria, viruses, fungi, parasites).

  • Virulence: Degree of pathogenicity (e.g., ability to infect, damage host tissue).

  • Endogenous Infections: Arise from normal flora due to changes in host immunity.

  • Opportunistic Infections: Occur when the body's defenses are weakened (e.g., in HIV patients).

  • Infectious Dose (ID): Minimum quantity of pathogen needed to cause disease (e.g., ID50).

• Steps in Pathogenesis:

  • Contact (Portals of Entry): Routes through which pathogens enter the host (e.g., skin, mucous membranes).

  • Adhesion: Mechanisms by which pathogens adhere to host tissues (e.g., pili, adhesins).

  • Establishment: Colonization of pathogens at the site of entry.

  • Movement to Sterile Tissues: Pathogen progression beyond initial site.

  • Tissue Damage: Lead to disease symptoms often caused by pathogen metabolic products or direct damage to tissues.

• Virulence Factors:

  • Endotoxins: Comprise part of the cell wall of Gram-negative bacteria, can trigger severe immune responses (e.g., septic shock).

  • Exotoxins: Secreted proteins from bacteria causing damage to host tissues (e.g., botulinum toxin).

• Types of Infections:

  • Local: Confined to a specific area (e.g., abscess).

  • Systemic: Spread throughout the body (e.g., sepsis).

  • Focal: Infection spreads from a local point to other areas (e.g., teeth infection spreading to jaw).

  • Asymptomatic: Carriers have no visible symptoms but can spread (e.g., Typhoid Mary).

  • Primary: Initial infection (e.g., flu) followed by secondary.

  • Secondary: Complication occurring after a primary infection (e.g., pneumonia following influenza).

• Portals of Exit:

  • Routes through which pathogens exit (e.g., respiratory tract, blood, feces).

Chapter 16

• Terminology:

  • Patterns of infectious disease occurrence clarified in public health contexts:

    • Endemic: Constant presence of a disease within a given geographic area (e.g., malaria in certain equatorial regions).

    • Pandemic: Outbreak occurring over a wide geographical area, crossing international boundaries (e.g., COVID-19).

• Modes of Disease Transmission:

  • Reservoir: Natural habitat of a pathogen, where it lives and multiplies (e.g., animals, humans).

  • Definitive Host: Organism where the pathogen reaches maturity (e.g., mosquito for malaria).

  • Intermediate Host: Organism that harbors immature stages of the pathogen (e.g., snails for schistosomiasis).

  • Source: Direct origin of the pathogen prior to transmission.

  • Carrier: Individual who harbors an infectious agent and can transmit it without showing symptoms (asymptomatic carriers).

• Transmission Methods:

  • Contact:

    • Direct Contact: Physical transfer of pathogens (e.g., touching, kissing).

    • Indirect Contact: Via inanimate objects (fomites, e.g., doorknobs, utensils).

  • Vehicle: Transmission via contaminated inanimate materials or organisms (e.g., food, water).

  • Vector: Living organisms that transmit pathogens (e.g., mosquitoes, ticks).

• Healthcare-Associated Infections (HAIs):

  • Nosocomial Infections: Infections acquired in healthcare settings, often resistant to treatment (e.g., MRSA).

  • Causes linked to invasive procedures, contaminated devices, or breach of standard protocols.

Chapter 17 - Innate Immunity

• Differences Between Innate and Adaptive (Acquired) Immunity:

  • Innate Immunity:

    • Immediate response, not pathogen-specific.

  • Adaptive Immunity:

    • Involves memory; develops after exposure, tailored to specific pathogens.

• Three Lines of Defense:

  • 1st Line:

    • Physical barriers (e.g., skin, mucous membranes) that prevent pathogen entry.

    • Chemical barriers: include secretions (e.g., tears, stomach acid).

  • 2nd Line: Non-specific responses.

    • Inflammatory response, phagocytosis, and fever mechanisms.

  • 3rd Line: Involves various immune cells like T and B cells, memory formation for future protection.

• Non-Specific Immune Defenses:

  • Physical Defenses:

    • Skin acts as a barrier; mucous traps pathogens.

  • Chemical Defenses:

    • Antimicrobial peptides present in skin secretions; low pH in stomach that inactivates many pathogens.

  • Cellular Defenses: White Blood Cells (WBCs), classified into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes).

    • Granulocytes facilitate inflammation and respond to parasites.

    • Agranulocytes include lymphocytes, which are crucial for adaptive immunity

• Actions of the Second Line of Defense:

  • Pathogen Recognition: Cells recognize pathogens via pattern recognition receptors (PRRs).

  • Inflammatory Response: Increase blood flow, recruit immune cells (e.g., WBCs).

  • Fever: Increased body temperature as a defense mechanism to inhibit pathogen growth.

  • Phagocytosis: The process by which cells (e.g., macrophages, neutrophils) engulf and digest pathogens.

  • Interferons: Proteins produced in response to viral infections, signaling neighboring cells to enhance defenses.

  • Complement System: A group of proteins in the blood that enhance immune response (e.g., opsonization).

Chapter 18 - Specific Immunity

• Adaptive Immunity:

  • Humoral Immunity (B cells): Produces antibodies against specific antigens.

  • Cell-Mediated Immunity (T cells): Involves T cell activation by antigens displayed by other cells (e.g., infected or cancerous cells).

• Antigens:

  • Epitopes: Specific portions of antigens recognized by the immune system.

  • Haptens: Small molecules that become immunogenic when attached to larger carrier proteins.

• Antibodies/Immunoglobulins:

  • Structure includes variable and constant regions; 5 main classes:

    • IgG: Most common, provides long-term immunity.

    • IgA: Found in mucosal areas, protects body surfaces.

    • IgM: First antibody produced in response to infection.

    • IgE: Involved in allergic responses and protection against parasites.

    • IgD: Mostly function unknown, assists in B cell activation.

• Antigen-Antibody Reactions/Interactions:

  • Neutralization, opsonization, agglutination, and activation of complement system are key mechanisms.

• MHC Molecules:

  • MHC Class I: Present on all nucleated cells, recognized by CD8+ cytotoxic T cells.

  • MHC Class II: Present on professional antigen-presenting cells and recognized by CD4+ helper T cells.

• Development of Lymphocytes:

  • B and T cells develop in bone marrow (B cells) and thymus (T cells).

  • Role of B-cell and T-cell receptors in recognizing specific antigens.

• Activation and Differentiation of Cells:

  • Helper T Cells assist in activating B cells and cytotoxic T cells through cytokine production.

  • Cytotoxic T Cells kill infected or cancerous cells.

  • Clonal Selection: Process by which specific lymphocytes proliferate and differentiate in response to an antigen.

• Types of Immunity and Vaccines:

  • Natural Immunity: Developing immunity through infection.

  • Artificial Immunity: Immunization or passive transfer of antibodies.

  • Active Immunity vs. Passive Immunity: Active involves stimulating the immune system, while passive involves receiving pre-formed antibodies (e.g., breast milk).

  • Classes of Vaccines: Live-attenuated, inactivated, subunit, and mRNA vaccines, each inducing specific immune responses.

  • Herd Immunity: When a significant portion of a population becomes immune, controlling the spread of disease.

Chapter 21 - Skin and Eye Infections

• Medical Terms for Skin Lesions and Rashes:

  • Lesion: Any abnormal tissue change inclusive of rashes or sores (e.g., macule, papule, vesicle).

• Bacterial Infections:

  • Bacterial Skin Infections:

    • Key genera like Staphylococcus: known for causing skin conditions (e.g., impetigo, cellulitis).

      • Staphylococcus aureus: Notorious for Methicillin-resistant Staphylococcus aureus (MRSA) infections.

    • Streptococcus: Causes conditions like scarlet fever and necrotizing fasciitis.

  • Pseudomonas aeruginosa: Opportunistic pathogen, common in burn victims.

  • Bacillus anthracis: Causes anthrax with clinical concerns in animal handlers; treated effectively with antibiotics.

• Bacterial Eye Infections:

  • Bacterial Conjunctivitis (Pinkeye): Highly contagious infection characterized by redness and discharge.

  • Neonatal Conjunctivitis: Affects newborns often due to Chlamydia or Gonorrhea from the mother.

  • Trachoma: Chronic eye infection leading to blindness, caused by Chlamydia trachomatis.

  • Bacterial Keratitis: Infection of the cornea causing pain, redness, and vision disturbances.

• Viral Infections:

  • Viral Skin Infections:

    • Human Papillomavirus (HPV): Leads to warts; certain strains are associated with cancers.

    • Human Herpesviruses: HSV-1 causes oral herpes; HSV-2 is related to genital herpes.

    • Human Parvoviruses: Cause fifth disease with characteristic “slapped cheek” rash.

  • Viral Eye Infections:

    • Herpetic (simplex) keratitis: Caused by HSV, leading to corneal damage.

    • Viral Conjunctivitis: Often caused by adenoviruses, characterized by watery discharge.

• Fungal Infections/Mycoses:

  • Mycoses of the Skin:

    • Tineas: Fungal infections like ringworm and athlete’s foot caused by dermatophytes.

    • Cutaneous Aspergillosis: Infection by Aspergillus, can occur in immunocompromised individuals.

    • Candidiasis: Overgrowth of Candida species leads to thrush and skin infections.

    • Sporotrichosis: Infection typically caused by Sporothrix, often from soil punctures.

• Parasitic Infections:

  • Protozoan and Helminthic Infections:

    • Acanthamoeba Infections: Rare but serious infections of the eye, skin, or nervous system.

    • Loiasis: Caused by the African eye worm, transmitted by the deer fly, presents with various symptoms, including eye discomfort.