Chapter 10: Mechanisms of Infectious Disease Pathophysiology

Flashcards covering terms, pathogen categories, disease triad, modes of transmission, epidemiology, stages, symptomatology, virulence factors, and diagnostics from Chapter 10: Mechanisms of Infectious Disease.

How is a host defined in the context of pathophysiology?

A host is any organism capable of supporting the nutritional and physical growth requirements of another organism.

What is colonization in infectious disease pathophysiology?

Colonization is the presence and multiplication of a living organism on or within a host.

What are saprophytes?

Saprophytes are free-living organisms that obtain their growth from dead or decaying organic material from the environment.

What is microflora?

Microflora refers to bacteria that inhabit exposed surfaces of the body.

How does virulence differ from a pathogen?

Virulence is the disease-inducing potential of a microorganism, whereas pathogens are microorganisms so virulent that they are rarely found without causing disease.

How do mutualism, commensalism, and parasitic relationships differ in host-microorganism interactions?

In mutualism, both the microorganism and the host derive benefits from the interaction. In commensalism, colonizing bacteria acquire nutritional needs and shelter while the host body is not affected. In a parasitic relationship, only the infecting organism benefits.

What three factors interact to result in an infectious disease according to the triad model?

Infectious diseases result from the interaction of an agent, a susceptible host, and environmental conditions that promote infection.

What are the primary microbial modes of transmission into the host body?

Transmission occurs through penetration (disruption in skin or mucous membrane integrity), direct contact (directly from infected tissue or excretions to intact mucous membranes), ingestion (through the oral cavity and GI tract), and inhalation (through the respiratory tract).

What are the structural and functional characteristics of viruses, and how are viral infections treated?

Viruses contain DNA or RNA enclosed in a protein coat (capsid) and cannot reproduce outside of host cells. They are treated with antivirals, which slow viral replication.

What structural components differentiate enveloped and non-enveloped virions?

Both non-enveloped and enveloped virions contain a nucleic acid genome (DNA or RNA) surrounded by a protein capsid; enveloped viruses possess an additional outer envelope surrounding the capsid.

What are four potential effects of viral infection on a host cell?

The four potential host cell outcomes are: lysis and death of the host cell, remaining latent within the cell, active replication causing disease, and transformation of the host cell into a malignant cell.

What is the cellular precursor of a prion and how does misfolding cause neurodegenerative disease?

Normal cellular precursor protein ($\text{PrP}^C$) misfolds into $\text{PrP}^{\text{SC}}$, forming $\beta$-pleated sheets. $\text{PrP}^{\text{SC}}$ aggregates accumulate, resisting enzymes and treatments, causing transmissible spongiform encephalopathies (such as Creutzfeldt-Jakob and Kuru) characterized by neuronal degeneration, vacuoles, amyloid plaques, ataxia, dementia, and death.

What bacterial shapes and arrangements are illustrated in bacterial classification?

Bacterial shapes and arrangements include Diplococci (pairs of spheres), Staphylococci (clusters of spheres), Streptococci (chains of spheres), Bacilli (rod-shaped), and Spirilla or spirochetes (spiral-shaped).

What features do organisms like Rickettsia, Anaplasma, Chlamydia, and Coxiella share with both viruses and bacteria?

Like viruses, they are obligate intracellular pathogens; like bacteria, they produce a rigid peptidoglycan cell wall, contain both RNA and DNA, and reproduce asexually by cellular division.

What are the three main types of parasites described in the lecture notes and their modes of transmission?

1. Protozoa: unicellular animals transmitted via person-to-person contact (sexual transmission), contaminated water or food, or vectors. 2. Helminths: tapeworms, roundworms, and flukes transmitted by ingesting fertilized eggs or through skin penetration. 3. Arthropods: ectoparasites such as mites, lice, and fleas.

What is the difference between prevalence and incidence in epidemiology?

Prevalence is the number of active cases of a disease at any given time, whereas incidence is the number of new cases of an infectious disease that occur within a defined population.

How are endemic, epidemic, and pandemic diseases differentiated?

An endemic disease is found in a particular geographic region with stable, expected incidence and prevalence. An epidemic is an abrupt and unexpected increase in disease incidence over endemic rates. A pandemic is the spread of disease beyond continental boundaries.

What distinguishes a nosocomial infection from a community-acquired infection?

A nosocomial infection is healthcare-associated and contracted while receiving care in a healthcare facility, whereas a community-acquired infection is contracted outside of healthcare settings in the general population.

What are the five stages of infectious disease progression?

1. Incubation period (time between pathogen exposure and symptom development), 2. Prodromal stage (initial appearance of symptoms), 3. Acute stage (rapid pathogen proliferation and maximum impact on host), 4. Convalescent stage (containment of infection, elimination of pathogen, symptom resolution, and tissue repair), and 5. Resolution (total elimination of microbe without residual signs/symptoms).

How are symptoms of infectious disease classified by site specificity and clinical presentation?

By site specificity: Specific symptoms reflect the exact site of infection (e.g., diarrhea, rash, convulsions, hemorrhage, pneumonia), whereas Nonspecific symptoms are shared by diverse diseases (e.g., fever, myalgia, headache, lethargy, malaise). By clinical presentation: Obvious symptoms follow predictable patterns (e.g., chickenpox, measles), whereas Covert symptoms require laboratory testing to detect (e.g., hepatitis, elevated white blood cell count).

What is the difference between bacterial endotoxins and exotoxins?

Endotoxins are lipopolysaccharides (LPS) located in the cell wall of Gram-negative bacteria that activate host monocytes and macrophages to release inflammatory mediators. Exotoxins are proteins released by bacteria during growth that directly inactivate or modify host cell structure or function.

What functions do adhesion, evasion, and invasion factors serve as bacterial virulence factors?

Adhesion factors allow microbes to attach to and colonize host tissues; Evasion factors help microbes evade the host immune system (e.g., encapsulation); Invasion factors are enzymes that facilitate microbial penetration through anatomic barriers and host tissue.

What criteria and diagnostic techniques are used to diagnose an infectious disease?

Diagnosis requires: 1. Recovery of a probable pathogen or evidence of its presence from infected host sites, and 2. Accurate documentation of compatible clinical signs and symptoms (symptomatology). Diagnostic techniques include culture (growing microorganisms outside the body), serology or antigen detection, and DNA/RNA sequencing.