Chapter 14_AFernando.pptx

Page 1: Introduction to Microbiology

• Title: Microbiology with Diseases by Body System

• Edition: Third Edition

• Chapter 14: Infection, Infectious Diseases, and Epidemiology

• Author: Robert W. Bauman

• Publisher: Pearson Education Inc., 2012

• Prepared by: Mindy Miller-Kittrell, North Carolina State University

Page 2: Symbiotic Relationships between Microbes and their Hosts

• Definition of Symbiosis: Means "to live together".

• Human-Microbe Relationships: Humans have countless symbiotic relationships with microorganisms.

• Types of Symbiosis:

  • Mutualism: Both organisms benefit.

  • Commensalism: One organism benefits, the other is neither helped nor harmed.

  • Parasitism: One organism benefits at the expense of the other.

Page 3: Normal Microbiota in Hosts

• Normal Flora: Organisms that colonize the body's surfaces without causing disease.

• Types of Microbiota:

  • Resident Microbiota: Always present; stable.

  • Transient Microbiota: Temporarily present; varies with environment and exposure.

Page 4: Resident Microbiota

• Characteristics:

  • Present throughout life.

  • Mostly commensal; benefit from host without causing damage.

  • Example: Staphylococcus epidermidis found on human skin.

Page 5: Table 14.2 - Some Resident Microbiota

• Upper Respiratory Tract Genera: Fusobacterium, Haemophilus, Lactobacillus, etc.

• Notes:

  • Nose has unique microbiota; trachea/bronchi are sparse.

  • Alveoli in lungs are axenic (no natural microbiota).

• Oral and Digestive Genera: Examples include Actinomyces, Bacteroides, Clostridium, etc.

• Skin Microbiota: Includes Corynebacterium, Micrococcus, etc., living on outer skin layers.

Page 6: Transient Microbiota

• Characteristics:

  • Temporary presence; cannot persist in the body.

  • Eliminated through competition, immune response, and changes in body conditions.

  • Handwashing can remove transient microorganisms.

Page 7: Acquisition of Normal Microbiota

• Womb Development: Initially axenic (free of microorganisms).

• Microbial Development: Begins during the birthing process; significant establishment occurs in the first few months of life.

Page 8: Opportunistic Pathogens

• Definition of Pathogen: Any microorganism causing disease.

• Opportunistic Pathogens: Normal microbiota that cause disease under certain conditions, such as immune suppression or introduction to unusual sites.

Page 9: Reservoirs of Infectious Diseases in Humans

• Definition of Reservoirs: Sites maintaining pathogens as sources of infection.

• Types of Reservoirs:

  • Animal Reservoirs: Diseases spreading from animals to humans; e.g., rabies.

  • Human Carriers: Asymptomatic individuals who can infect others.

  • Nonliving Reservoirs: Soil, water, food contaminated with pathogens.

Page 10: Animal Reservoirs

• Zoonoses: Diseases transmitted from animals to humans.

• Contract Routes:

  • Direct contact with animals or waste (e.g., rabies).

  • Consumption of animals (e.g., salmonellosis).

  • Through bloodsucking insects (e.g., yellow fever).

• Dead-End Host: Humans often cannot transmit zoonotic pathogens further.

Page 11: Human Carriers

• Asymptomatic Individuals: Infect others without showing symptoms.

• Outcomes in Carriers: Some remain healthy, while others may develop illness later.

Page 12: Nonliving Reservoirs

• Common Reservoirs: Soil, water, food contaminated by animal waste.

• Fomites: Inanimate objects that aid in indirect transmission of pathogens.

Page 13: Exposure to Microbes

• Contamination: Presence of microbes on the body.

• Infection: Pathogen evades the body's defenses and establishes itself.

• Portals of Entry:

  • Skin

  • Mucous membranes

  • Placenta

  • Parenteral route

Page 14: Routes of Entry for Invading Pathogens

• Common Entry Points:

  • Broken skin

  • Insect bites

  • Conjunctiva of the eye

  • Nose, mouth, vagina, urethra

  • Through placenta in some cases

Page 15: Portals of Entry: Skin

• Function of Skin: Acts as a barrier against pathogens.

• Pathogen Entry: Possible through openings, cuts, or by burrowing into or digesting skin layers.

Page 16: Portals of Entry: Mucous Membranes

• Function: Lines cavities open to the environment, providing warmth and moisture.

• Common Entry Point: Respiratory tract (nose/mouth), gastrointestinal tract is also a route but must survive acidic conditions.

Page 17: Portals of Entry: Placenta

• Barrier Function: Generally effective in blocking pathogens.

• Pathogen Crossing: Some can cross to infect the fetus, leading to severe consequences such as abortion or birth defects (e.g., Treponema pallidum causing syphilis).

Page 18: Portals of Entry: Parenteral Route

• Definition: Circumvents natural portals of entry by depositing pathogens directly into tissues beneath skin/mucous membranes.

Page 19: Role of Adhesion in Infection

• Adhesion: Process where microorganisms attach to host cells, crucial for colonization.

• Adhesion Factors: Specialized structures and attachment proteins assist in adherence to cells.

Page 20: Nature of Infectious Disease

• Definition of Infection: Invasion of host by a pathogen.

• Disease Definition: Results if pathogen disrupts normal body functions (termed morbidity).

• Manifestations of Disease:

  • Symptoms: Subjective feelings (e.g., aches).

  • Signs: Objective measures (e.g., fever).

  • Syndromes: Combination of symptoms/signs of a specific disease (e.g., AIDS).

  • Asymptomatic Infections: Lack symptoms but may have detectable signs.

Page 21: Causation of Disease: Etiology

• Etiology: The study of disease causes.

• Germ Theory of Disease: Diseases caused by pathogenic microorganisms.

• Koch's Postulates: Established by Robert Koch to link specific pathogens to specific diseases.

Page 22: Virulence Factors of Infectious Agents

• Pathogenicity: Organism's ability to cause disease.

• Virulence: Degree of pathogenicity influenced by virulence factors such as:

  • Adhesion factors (e.g., pili)

  • Biofilms

  • Extracellular enzymes

  • Toxins

  • Antiphagocytic factors (e.g., capsules)

Page 23: Virulence Factors: Extracellular Enzymes

• Function: Enzymes secreted by pathogens to

  • Dissolve body structural chemicals

  • Aid in infection maintenance, invasion, and evasion of immune responses.

  • Examples include hyaluronidase and collagenase for tissue invasion.

Page 24: Virulence Factors: Toxins

• Definition of Toxins: Chemicals that damage host tissues or trigger harmful immune responses.

• Toxemia: Toxins in the bloodstream affecting distant body sites.

• Types of Toxins:

  • Endotoxins: Part of cell walls, typically less toxic.

  • Exotoxins: Secreted by pathogens, usually more toxic.

Page 25: Virulence Factors: Antiphagocytic Factors

• Purpose: Prevent pathogens from being engulfed by phagocytic cells.

• Mechanisms Include:

  • Capsules made of non-recognized chemicals

  • Antiphagocytic chemicals that hinder phagocytosis

  • Leukocidins that kill white blood cells

Page 26: Stages of Infectious Disease

• Disease Process: Follows infection with typical stages:

  • Incubation Period: No symptoms present.

  • Prodromal Period: Vague, general symptoms emerge.

  • Illness: Most severe signs and symptoms appear.

  • Decline: Symptoms begin to decrease.

  • Convalescence: Resolution of symptoms, recovery ensues.

Page 27: Portals of Exit

• Definition: Pathways by which pathogens leave the host.

• Common Portals of Exit:

  • Ears (earwax), skin (flakes, blood), anus (feces), urethra (urine), mouth (saliva), and female reproductive system (secretions).

Page 28: Transmission of Infectious Disease

• Transmission Mechanisms:

  • Contact: Direct, indirect (via fomites), or droplet (aerosols).

  • Vehicle: Transmission via airborne, waterborne, or foodborne pathways.

  • Vector: Transmission through biological or mechanical vectors (e.g., insects).

Page 29: Classification of Infectious Diseases

• Methods of Classification:

  • Body systems they affect.

  • Longevity and severity.

  • Modes of transmission.

  • Effects on populations instead of individuals.

• Terms Used:

  • Acute, chronic, subacute, latent, communicable, contagious.

Page 30: Epidemiology: Frequency of Disease

• Disease Measurement:

  • Incidence: New cases over a given area and time.

  • Prevalence: Total cases over a given area and time.

• Evaluating Frequency: Involves both frequency and geographic distribution.

Page 31: Figure 14.14

• Description: Curves representing incidence and prevalence of AIDS among U.S. adults over time (data not provided).

Page 32: Epidemiological Terminology

• Endemic: Constantly present disease at low levels in the population.

• Epidemic: Unusual high occurrence of disease in a population simultaneously.

• Pandemic: Global epidemic affecting a large number of people.

• Sporadic: Occurring irregularly, isolated cases found.

Page 33: Figure 14.16

• Illustrations: Different terms for disease occurrence including endemic, sporadic, epidemic, and pandemic (data/images not provided).

Page 34: Epidemiological Studies: Descriptive Epidemiology

• Description: Involves careful data collection on diseases, including time and location of cases.

• Index Case: Identification of the first known case in an area or population.

Page 35: Epidemiological Studies: Analytical Epidemiology

• Purpose: Determine cause, mode of transmission, and prevention strategies.

• Conditions: Useful in cases where Koch’s postulates cannot be experimentally applied.

Page 36: Epidemiological Studies: Experimental Epidemiology

• Definition: Involves testing hypotheses about disease causes.

• Koch’s Postulates: Application of which leads to conclusions in experimental epidemiology.

Page 37: Hospital Epidemiology

• Nosocomial Infections: Infections acquired during hospital stays.

• Types of Nosocomial Infections:

  • Exogenous: Pathogens acquired from the healthcare environment.

  • Endogenous: Pathogens from the patient's own microbiota.

  • Iatrogenic: Related to modern medical procedures.

Page 38: Figure 14.20

• Components: Factors contributing to nosocomial infections such as environmental microorganisms, immunocompromised patients, and cross-transmission among individuals (data/images not provided).

Page 39: Control of Nosocomial Infections

• Precautionary Measures: Designed to minimize infection rates.

• Handwashing: Most effective method for reducing the incidence of nosocomial infections.

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