Microbiology Exam 3 Study Guide

Lecture 14 - Concepts in Antimicrobial Control

  • Main Concepts in Antimicrobial Control

    • Sterilization

    • Disinfection

    • Decontamination (Sanitization)

    • Antisepsis (Degermination)

  • Microbial Control Methods

    • Physical Agents

    • Moist (e.g., boiling, autoclaving)

    • Dry (e.g., hot air, incineration)

    • Radiation (ionizing, nonionizing)

    • Cold (refrigeration, freezing)

    • Pressure

    • Chemical Agents

    • High-level Germicides

    • Intermediate-level Germicides

    • Low-level Germicides

      • Dilution: Parts per million (ppm) and percentage solution

  • Factors Affecting Germicidal Activity

    • Concentration of germicide

    • Presence of organic matter

    • Duration of exposure

    • Temperature and pH

    • Nature of microorganisms being treated

Lecture 15 - Antimicrobial Chemotherapy/Antimicrobial Drugs

  • Antibiotics

    • Discovery Revolutionized Healthcare

    • Antibiotics are metabolic products of bacteria and fungi that inhibit competing microbes.

    • Key sources: Bacteria from the genera Streptomyces and Bacillus, and molds from Penicillium and Cephalosporium.

  • Techniques and Concepts

    • Kirby-Bauer Technique

    • An agar plate method to test sensitivity of bacteria to specific antibiotics by measuring zones of inhibition.

    • Therapeutic Index (TI)

    • TI is the ratio of the toxic dose (TD50) to the effective dose (ED50).

    • A high TI indicates wide safety margin; a low TI requires careful monitoring.

    • Selective Toxicity

    • The ability to target microbial cells without affecting host cells.

  • Drug Resistance

    • Definition: Microorganisms adapt to tolerate drugs (can be intrinsic or acquired through mutations or horizontal gene transfer).

    • Mechanisms of resistance include spontaneous mutations and acquisition of resistance through plasmids.

  • Probiotics vs Prebiotics

    • Probiotics: Live microorganisms to improve gut health.

    • Prebiotics: Foods that support growth of beneficial bacteria.

  • Drug Toxicity and Allergies

    • Side effects can affect crucial organs and body systems, which may lead to serious health issues.

    • Drug allergies can develop upon re-exposure after initial contact with the drug.

Lecture 16 - Human Microbiome

  • Definition

    • The Human Microbiome: The collection of all microbes residing on and in the human body, essential for health.

  • Pathogenicity and Virulence

    • Pathogen: Microbe capable of causing disease.

    • Pathogenicity: The ability to cause disease, differing between true and opportunistic pathogens.

    • Virulence: The degree of pathogenicity, often determined by specific virulence factors.

  • Bacterial Entry and Pathogenicity - Five Steps

    1. Portal of Entry: Where microbes enter (exogenous or endogenous).

    2. Attachment/Adhesion: Pathogens attach to host cells using pili/fimbriae.

    3. Surviving Host Defenses: Strategies against phagocytosis, including the use of leukocidins and capsules.

    4. Causing Damage: Via toxins (endotoxins vs exotoxins) or eliciting an excessive immune response.

    5. Portal of Exit: Routes of pathogen exit from the host (e.g., secretions, excretions).

  • Types of Toxins

    • Endotoxins: Part of Gram-negative bacteria's outer membrane, can cause systemic reactions.

    • Exotoxins: Proteins secreted by bacteria, can directly damage host tissues.

  • Signs and Symptoms of Infection

    • Symptoms: Subjective; Signs: Objective (e.g., fever, inflammation).

  • Stages of Infection

    • Incubation > Prodromal > Acute > Convalescent > Continuation.

  • Reservoirs of Infection

    • Living (humans, zoonotic) and nonliving (water, soil).

Lecture 17 - Immunopathology

  • Definitions

    • Immunopathology: Study of diseases from immune system overactivity or underactivity.

  • Types of Sensitivity (Hypersensitivity)

    • Type I: Common allergies (IgE-mediated) such as anaphylaxis.

    • Type II: Cytotoxic reactions (IgG/IgM mediated).

    • Type III: Immune complex reactions.

    • Type IV: Delayed-type hypersensitivity (T-cell mediated).

  • Type I Hypersensitivity

    • Common allergies ranging from mild to potentially fatal anaphylactic reactions.

    • Allergens can be inhaled, ingested, injected, or contact allergens.

  • Clinical Manifestations

    • Hay fever and asthma, involving various immune mediators and symptoms.

  • Drug Allergies

    • Common, with potential for severe adverse effects; diagnostic methods include blood tests and skin tests.

  • Types of Grafts

    • Autograft, Isograft, Allograft, Xenograft.

  • Importance of Monitoring

    • Continuous evaluation of drug effectiveness and potential side effects in therapeutic settings.