Chapter 11 Study Guide

Part 1: Normal Microbiota and Host Interactions

Objective 1: Define colonization, infection, and disease.

• Colonization: Microbes are present in the host but do not cause disease.

• Infection: Microbes get past host defenses, enter tissues, and multiply, producing inflammation.

• Disease: The effects of infection damage or disrupt tissues and organs.

• Infectious disease: A pathologic state caused directly by microorganisms or their products.

Key distinction: Colonization does not necessarily cause disease. Infection involves microbial multiplication, while disease involves tissue or organ damage or dysfunction.

Objective 2: Describe commensalism, mutualism, and parasitism.

Types of parasites mentioned in the notes:

• Obligate: Requires a host (example: virus).

• Facultative: Can be free-living and then use a host.

• Endoparasite: Lives inside a host.

• Ectoparasite: Lives outside a host.

Objective 3: Identify sites where normal biota are found and not found in humans.

According to the table on slide 9:

Important: The lecture emphasizes that the Human Microbiome Project has challenged older ideas about which body sites are sterile. Detection of microbial DNA does not necessarily establish the presence of living, resident microbes.

Objective 4: List factors that weaken host defenses and allow disease.

1. Old age and extreme youth (infancy or prematurity)

2. Genetic or acquired immune defects, including AIDS

3. Surgery and organ transplants

4. Underlying diseases, including cancer, liver malfunction, and diabetes

5. Chemotherapy and immunosuppressive medications

6. Physical and mental stress

7. Pregnancy

8. Other infections

These factors increase susceptibility to infection.

Objective 5: Name five sources where newborns acquire microbiota.

According to the infographic on slide 13:

1. In utero: Exposure to microbes before birth, as presented in the lecture.

2. Birth: Vaginal birth and C-section contribute different initial microbiomes.

3. Milk: Breast milk contains a microbiome; sterilized formula does not.

4. Caregivers: Family members, siblings, and others share microbes with the baby.

5. Environment: Babies acquire microbes from things they contact.

Part 2: Pathogenicity and Virulence

Objective 6: Differentiate between pathogenicity and virulence.

Remember: Pathogenicity concerns whether a microbe can cause disease; virulence concerns its ability to establish infection and cause damage.

Objective 7: List the steps a microbe must take to cause disease.

1. Find a portal of entry: Enter the host through an appropriate route

2. Attach to host cells: Establish a foothold using structures such as fimbriae, capsules, or surface proteins

3. Survive host defenses: Avoid phagocytosis or survive inside phagocytes

4. Cause damage (disease): Damage tissues through enzymes, toxins, host responses, or epigenetic changes

5. Exit the host: Leave through secretions, excretions, discharge, or other portals

Objective 8: Explain the significance of polymicrobial infections.

Polymicrobial infections: Infections involving more than one microorganism.

• The lecture states that the majority of infections are polymicrobial.

• An initial infection can be associated with another infection.

Example: An influenza infection frequently leads to pneumonia.

Objective 9: List several portals of entry and exit.

Microbes can leave through secretion, excretion, discharge, or sloughed tissue.

Objective 10: Define infectious dose and explain its role in establishing infection.

Infectious dose (ID): The minimum number of microbes necessary for an infection to proceed.

• Microorganisms with smaller infectious doses have greater virulence, according to the lecture.

• Different pathogens require different numbers of microbes to establish infection.

Objective 11: Describe three ways microbes cause tissue damage.

1. Enzymes or toxins: Microbes directly damage host tissues using enzymes, endotoxins, or exotoxins.

2. Excessive or inappropriate host response: Microbes trigger host defenses that cause tissue damage.

3. Epigenetic changes: Microbes cause changes in host cells that affect their function.

Objective 12: Define and give an example of four exoenzymes.

Exoenzymes: Enzymes secreted by microbes that break down and damage host tissues or dissolve protective barriers, allowing disease to spread.

Objective 13: Compare and contrast endotoxins and exotoxins.

Examples of exotoxin effects:

• Neurotoxins affect the nervous system.

• Enterotoxins affect the intestines.

• Hemotoxins lyse red blood cells.

• Nephrotoxins damage the kidneys.

Endotoxin effects: Fever, inflammation, hemorrhage, diarrhea, and potentially fatal endotoxic shock.

Objective 14: Differentiate between a sign and symptom.

• Sign: Objective evidence of disease observed by another person.

• Symptom: Subjective evidence of disease experienced by the patient.

• Syndrome: A disease identified by a characteristic combination of signs and symptoms.

Objective 15: List and describe signs of a blood infection.

These are the terms and distinctions used in the lecture slides.

Objective 16: Define asymptomatic, pathogen, and sequelae.

• Asymptomatic (subclinical): An infection in which the microbe is active in host tissues but produces no noticeable symptoms.

• Pathogen: A microorganism whose relationship with the host is parasitic and results in infection and disease.

• Sequelae: Long-term or permanent damage to tissues or organs caused by an infectious disease.

Examples of sequelae from the lecture:

Objective 17: Define virulence factors.

Virulence factors: Characteristics, structures, or adaptations that contribute to a microbe's ability to establish itself in a host and cause damage.

Examples mentioned in the lecture include fimbriae, capsules, surface proteins, leukocidins, enzymes, and toxins.

Objective 18: Draw a diagram of the five stages of disease and list their characteristics.

Part 3: Reservoirs and Disease Transmission

Objective 19: Define the four types of reservoirs and provide examples.

Reservoir: The primary habitat of a pathogen. Reservoirs can include humans, animals, soil, water, and plants.

The slides distinguish living and nonliving reservoirs. The following four categories summarize the sources identified in the lecture.

The lecture also lists plants as possible reservoirs.

Objective 20: List several modes of transmission of infectious agents.

• Direct contact: Transmission through close contact between individuals.

• Indirect transmission: An object or substance carries an infectious agent.

• Vector transmission: Arthropods harbor and transfer infectious agents to humans.

• Vertical transmission: An infectious agent passes from parent to offspring.

Examples of vectors from the notes include mosquitoes, fleas, flies, and ticks.

Objective 21: Describe five types of carriers and give an example.

Carrier: An individual who harbors an infectious agent and may serve as a source of infection.

Objective 22: Differentiate between horizontal and vertical transmission.

Key distinction: Horizontal = between individuals; vertical = parent to offspring.

Objective 23: Define healthcare-associated infection and list two most common types.

Healthcare-associated infection (HAI), also called a nosocomial infection: An infectious disease acquired or developed during a hospital or healthcare facility stay.

The lecture lists five common types:

1. Pneumonia

2. Gastrointestinal infections

3. Urinary tract infections (UTIs)

4. Bloodstream infections

5. Surgical site infections

The slides do not rank these five, so they do not establish which two are the most common.

Factors contributing to HAIs: Compromised patients, concentrations of pathogens in healthcare facilities, and exposure through equipment, fomites, patients, personnel, visitors, air, or water.

Objective 24: Define reservoir, transmitter, zoonosis, communicable, contagious, and noncommunicable.

Examples from the lecture:

• Communicable/contagious: Influenza and measles are highly contagious.

• Weakly communicable: Hansen's disease (leprosy).

• Zoonosis: Rabies.

• Noncommunicable infection: An individual develops an infection from their own microbiota or from a nonliving reservoir without transmitting it to others.

Reservoir vs. transmitter:

• Syphilis: The reservoir and transmitter can be the same person.

• Hepatitis A: The reservoir is a human, while contaminated food can act as the transmitter.

Part 4: Epidemiology

Objective 25: Summarize the goals of epidemiology and differentiate it from traditional medical practice.

Epidemiology: The study of the frequency and distribution of disease and other health-related factors in defined populations.

Goals and techniques described in the lecture:

1. Identify causative agents of disease.

2. Investigate sources and modes of transmission.

3. Track behaviors such as exercise and smoking.

4. Study disease pathology.

5. Track the number and distribution of cases in communities.

The lecture specifically describes epidemiology's population-level focus; the comparison with individual patient care is a simplified distinction.

Florence Nightingale: Helped establish modern epidemiology by documenting disease-related deaths and improving sanitation in military hospitals.

Objective 26: Explain what is meant by a disease being notifiable or reportable and provide examples.

Notifiable or reportable disease: A disease that must be reported to public health authorities.

• Certain diseases require mandatory reporting.

• Other diseases may be reported voluntarily.

• Reports help public health departments track diseases.

Note: The lecture defines reportable diseases but does not identify specific diseases that are legally reportable. Therefore, examples cannot be confirmed from the provided notes alone.

Objective 27: Define incidence and prevalence and explain the difference.

Formulas from the lecture:

\[ \text{Incidence}=\frac{\text{New cases during a time period}}{\text{Susceptible population}} \]

\[ \text{Prevalence}=\frac{\text{Total existing cases}}{\text{Total population}}\times100 \]

Examples from the slides:

• Incidence: New tuberculosis cases in the United States in 2018 were 2.8 per 100,000.

• Prevalence: The lecture uses 14% as an example of smoking prevalence among U.S. adults.

Remember: Incidence = NEW cases. Prevalence = ALL existing cases.

Objective 28: Define the following epidemiological terms.

Quick comparison of disease occurrence

Endemic

Relatively steady

Sporadic

Occasional cases

Epidemic

Above expected level

Pandemic

Across continents

Illustrative patterns based on the definitions in the lecture.