Ch_15___16__Microbial_Mechanisms_of_Pathogenicity__Disease_and_Epidemiology__S_

BACT 1003 Chapter 15 & 16 Overview

Microbial Mechanisms of Pathogenicity

• Focuses on understanding how pathogens cause diseases and the dynamics of disease spread through various mechanisms.

Key Chapters

• 15.1 Characteristics of Infectious Disease: Examines various attributes and impacts of infectious diseases on health and society.

• 15.2 How Pathogens Cause Disease: Discusses the essential processes pathogens use to invade and affect host organisms.

• 15.3 Virulence Factors of Bacterial and Viral Pathogens: Identifies specific traits that enhance the ability of bacteria and viruses to cause disease.

• 15.4 Virulence Factors of Eukaryotic Pathogens: Explains the mechanisms employed by fungi, protozoa, and helminths to cause disease.

• 16.1 The Language of Epidemiologists: Introduces key terminology used in the field of epidemiology to analyze disease patterns.

• 16.3 Modes of Disease Transmission: Covers the various ways infectious diseases are spread among populations.

Page 1 - Introduction to Infectious Diseases

• Dynamic equilibrium: The balance of interactions between host health and microbial populations.

• Healthy vs. Infectious: Differentiates between normal flora (beneficial microorganisms) and pathogenic organisms (harmful).

• Human-Microbe Interaction: Explores the complexities of the ecosystems formed by human hosts and their microbial inhabitants.

• Development of Biofilms: Describes how communities of microorganisms form protective layers on surfaces, impacting health and disease outcomes.

Page 2 - Human-Microbe Interactions

• Normal Microbial Residents:

  • Beneficial microbes that reside in the human body without causing disease.

  • Help in digestion, vitamin synthesis, and immune system function.

• Stages of Infection:

  • Incubation: Period between exposure to the pathogen and the appearance of symptoms.

  • Prodromal stage: Onset of general symptoms indicating the start of infection.

  • Period of illness: When specific symptoms manifest, showing the active disease stage.

  • Period of decline: Symptoms begin to subside as the body starts to recover.

  • Convalescent period: Recovery stage where the body returns to health.

• Epidemiology:

  • The scientific study focused on how disease spreads and affects populations.

  • Important for controlling outbreaks and establishing public health policies.

Page 3 - Key Terminology

• Pathology: Study of diseases, their causes, and effects on the organism.

• Etiology: The investigation into the origins and reasons behind diseases.

• Pathogen: Microorganisms, including bacteria, viruses, fungi, and parasites, that can cause disease.

• Pathogenesis: Study of the development and progression of diseases.

• Infection: Successful colonization of a host by pathogens.

• Disease: An abnormal condition that affects normal bodily functions, often accompanied by specific symptoms.

Page 4 - Signs and Symptoms of Disease

• Sign: Objective indication of disease that can be observed or measured (e.g., rash, fever).

• Symptom: Subjective experience or change in bodily function reported by the patient (e.g., pain, fatigue).

• Syndrome: A cluster of signs and symptoms that collectively indicate a particular disease or condition.

Page 5 - Nomenclature of Symptoms

• Prefixes and Suffixes: Important for understanding medical terms related to conditions.

  • Examples include:

    • cyto-: Relating to cells.

    • hepat-: Related to the liver.

    • -pathy: Indicating disease.

• Examples:

  • cytopenia: Reduction in blood cells.

  • hepatitis: Inflammation of the liver.

Page 6 - Classifications of Disease

• Infectious Diseases: Result from the action of pathogens invading the body.

• Noninfectious Diseases: Conditions not caused by pathogens, often resulting from genetics or lifestyle choices.

Page 7 - Specific Diseases

• Plasmodium falciparum: The organism responsible for malaria, a serious zoonotic disease.

• Sickle Cell Disease: A genetic disorder characterized by abnormal hemoglobin, noninfectious in nature.

Page 8 - Disease Classifications

• Communicable Diseases: Infectious diseases that can be transmitted from one person to another.

• Noncommunicable Diseases: Conditions not spread through person-to-person contact.

• Iatrogenic Diseases: Disorders caused as a result of medical treatment or procedures.

• Zoonotic Diseases: Diseases transmitted from animals to humans.

Page 9 - Periods of Disease

• Classifies the stages of clinical infections:

  • Incubation period: Pathogen is present but symptoms are not.

  • Prodromal stage: Early signs are vague and nonspecific.

  • Period of illness: Symptoms are at their peak.

  • Period of decline: Symptoms decrease.

  • Convalescent period: Recovery begins, potential still for transmission.

Page 10 - Duration of Disease

• Acute Disease: Characterized by a rapid onset and short duration.

• Chronic Disease: Develops slowly and can last for long periods, often years.

• Latent Disease: The pathogen is dormant but can reactivate and cause symptoms later on.

Page 11 - Koch's Postulates

• Criteria for establishing a causal relationship between a pathogen and a disease:

  • Pathogen must be found in diseased hosts, absent in healthy ones.

  • Pathogen should be isolated and grown in pure culture.

  • Pathogen must cause disease when introduced to a healthy host.

  • Pathogen should be re-isolated from the newly diseased host.

Page 12 - Normal Microbiota

• Refers to beneficial microorganisms that exist in mutualistic relationships with the host.

  • Comprises both transient flora (temporary) and resident flora (permanent).

Page 13 - Distribution of Microbes

• Analysis of microbiota distribution on various body surfaces, influencing health.

Page 14 - Sterile Sites

• Anatomical locations within the body that are typically free from microorganisms, such as heart and cerebrospinal fluid.

Page 15 - Microbial Antagonism

• The protective role of normal flora against harmful microbes through competition and resource utilization.

Page 16 - Pathogen Classifications

• Primary Pathogens: Infectious agents that cause disease in healthy individuals.

• Opportunistic Pathogens: Microorganisms that only cause disease in a weakened immune system.

Page 17 - Infectious Dose (ID)

• The minimum number of pathogens needed to establish an infection in a host.

  • A small ID value indicates higher virulence of the pathogen.

Page 18 - Pathogenicity and Virulence

• Pathogenicity: The inherent ability of a pathogen to cause disease.

• Virulence: The degree of pathogenicity, determined by specific attributes of the pathogen.

• Virulence Factors: Traits that enhance a pathogen’s ability to invade hosts and induce damage.

Page 19 - Antiphagocytic Factors

• Mechanisms by which pathogens evade phagocytosis, including:

  • Presence of a slime layer or capsule.

  • Ability to survive within phagocytes after ingestion.

Page 20 - Exoenzymes

• Enzymatic substances produced by pathogens to dissolve barriers and aid in invasion:

  • Examples: Hyaluronidase, DNAse, Collagenase.

Page 21 - Blood Vessel Illustration

• Visuals demonstrating the role of collagenase in facilitating bacterial entry into the bloodstream.

Page 22 - Toxins Overview

• Two primary types of bacterial toxins:

  • Endotoxins: Part of the bacterial cell wall; induce general symptoms.

  • Exotoxins: Secreted by bacteria; cause specific cellular damage.

Page 23 - Comparison of Toxins

• Endotoxin Characteristics:

  • Generalized symptoms, high lethality (measured as LD50).

• Exotoxin Characteristics:

  • Targeted damage to cells, varying heat stability, and lower lethality.

Page 24 - Common Exotoxins

• Notable examples include:

  • Cholera toxin: Disrupts ion transport in intestinal cells.

  • Tetanus toxin: Interferes with nerve signaling.

  • Diphtheria toxin: Inhibits protein synthesis in host cells.

Page 25 - Mechanisms of Toxins

• Botulinum Toxin: Paralyzes muscles by blocking acetylcholine release.

• Tetanus Toxin: Causes sustained muscle contractions by preventing muscle relaxation.

Page 26 - Stages of Pathogenesis

• The process through which a pathogen leads to disease:

  • Exposure: Contact with pathogens.

  • Adhesion: Attachment to host cells.

  • Invasion: Penetration into tissues.

  • Infection: Reproductive success in the host leading to disease symptoms.

Page 27 - Portals of Entry

• Exogenous: Microbes entering the body from the external environment.

• Endogenous: Microbes originating from within the host (e.g., normal flora).

Page 28 - Pathogens During Pregnancy

• TORCH Infections: A group of pathogens that can cause complications during pregnancy:

  • Toxoplasmosis

  • Other pathogens

  • Rubella

  • Cytomegalovirus

  • Herpes

Page 29 - Adhesion Factors

• Characteristics that enable pathogens to adhere effectively to body cells:

  • Examples include glycocalyx presence in biofilms.

Page 30 - Invasion of Pathogens

• Following adhesion, pathogens penetrate local tissues, often leading to the establishment of infection.

Page 31 - Types of Infection

• Infection classifications based on spread and severity:

  • Localized: Confined to one area (e.g., boil).

  • Systemic: Spreads throughout the body (e.g., flu).

  • Focal: Starts in one location and spreads to others.

  • Mixed: Involvement of multiple pathogens.

  • Primary: Initial infection.

  • Secondary: An infection resulting from an initial infection.

Page 32 - Portals of Exit

• Pathogens exit their host through various methods, including:

  • Coughing/sneezing, shedding of skin cells, and fecal matter.

Page 33 - Introduction to Disease and Epidemiology

• Overview of the chapters discussing disease spread, identification, and epidemiological analysis.

Page 34 - Key Epidemiological Terminology

• Epidemiology: The study of how diseases impact populations and factors influencing their spread.

• Morbidity and Mortality: The rates of illness and death, respectively, related to specific diseases.

• Incidence and Prevalence: Measures of the occurrence of new and existing cases within populations over time.

Page 35 - HIV Statistics

• Graph and data illustrating the trends in HIV incidence and prevalence in the U.S. from 1980 to 2010, highlighting the epidemic's evolution.

Page 36 - CDC Role

• The Centers for Disease Control and Prevention (CDC) is responsible for:

  • Collecting and analyzing epidemiological data.

  • Publishing reports to inform public health strategies.

Page 37 - Patterns of Disease Occurrence

• Endemic: Diseases present in a population at relatively stable rates.

• Sporadic: Occasional cases occurring irregularly.

• Epidemic: Rapid increase in disease occurrence above normal expected levels.

• Pandemic: Global spread of disease affecting multiple countries.

Page 38 - Reservoirs and Carriers

• Reservoir: The natural habitat in which a pathogen thrives.

• Carrier: Individual who harbors a pathogen and can spread it, may be symptomatic or asymptomatic.

Page 39 - Contact Transmission

• Direct Transmission: Spread of disease via immediate contact between individuals.

• Indirect Transmission: Infection transmitted through contaminated surfaces or materials.

Page 40 - Vehicle Transmission

• Methods by which pathogens spread through various vehicles including:

  • Airborne: Suspended in air, inhaled by hosts.

  • Waterborne: Contaminated water sources.

  • Foodborne: Through improperly prepared food items.

Page 41 - Vector Transmission

• Types of vectors involved in disease spread:

  • Biological Vectors: Organisms that play a role in the lifecycle of pathogens (e.g., mosquitoes transmitting malaria).

  • Mechanical Vectors: Transport pathogens without being part of the pathogen life cycle (e.g., flies carrying bacteria on their legs).

Page 42 - Healthcare-Associated Infections (HAIs)

• Also known as Nosocomial infections; these infections are acquired in medical settings due to increased vulnerability of patients, highlighting the importance of healthcare practices in preventing disease transmission.