mechanisms of infectious disease Chapter 10

Host

Any organism capable of supporting the nutritional and physical growth requirements of another organism

Infectious disease

The disease state brought about by the interaction with another organism

Colonization

The presence and multiplication of a living organism on or within the host

Microflora

Bacteria inhabiting exposed surfaces of the body

Virulence

The disease inducing potential

Pathogens

Microorganisms so virulent that they are rarely found in the absence of disease

Saprophytes

Free living organisms obtaining their growth from dead or decaying organic material from the environment

Mutualism

An interaction in which the microorganism and the host both derive benefits from the interaction

Commensalism

An interaction in which colonizing bacteria acquire nutritional needs and shelter but the host body is not affected

Parasitic relationship

Only the infecting organism benefits from the relationship

Infectious disease

The host sustains injury or pathologic damage

What does infectious diseases results from?

Agent

Host

Environment

Common pathogens

Viruses

Bacteria

Fungi

Protozoa

Worms

Prion

Prions

Protein particles that can transmit infection by self- propagation

Viruses

The smallest obligate intracellular pathogen

caspid surrounding DNA or RNA genome

may also have an envelope

cannot replicate on their own-must use a host cell to replicate

Epstein-Barr virus (EBV)

Invades and replicates in salivary glands or pharyngeal epithelium which sends into saliva and respirators recreations

Bacteria

Autonomously replicating prokaryotes enclosed with a rigid cell wall

divide by cellular division

Rickettsia, Anaplasma, Chlamydia, Coxiella

Organisms that combine characteristics of viral and bacterial agents to produce disease in humans

Protozoa

Unicellular animals

Transmitted through person-to person contact, contaminated water or food, vector

Helminths

Tapeworm, roundworm, flutes

Transmission through ingesting fertilized eggs or penetration through skin

Anthropoids

Mites, lice, fleas

Epidemiology

The study of factors, events, and circumstances that influence the transmission of infectious disease among humans

Incidence

The number of new cases of an infectious disease that occur within a defined population

Prevalence

The number of active cases at any given time

Endemic disease

Found in a particular geographic region

Epidemic

abrupt and unexpected increase in the incidence of disease over endemic rates

Pandemic

spread of disease beyond continental boundaries

Portal of entry

The process by which a pathogen enters the body,gains access to tissues, and causes disease

Penetration

Any disruption in integrity of skin or mucous membranes

Direct contact

Directly from infected tissue or excretions to intact mucous membrane

Ingestion

Through oral cavity and GI tract

Inhalation

Through respiratory tract

Several mechanisms microbes establish infection and damaged tissue

Enter host cells and directly causing cell death

Induce host responses that damage host tissue

Generate virulence factors

Generate virulence factors

Substance made by microbe that enhance ability to cause disease

Specific

Reflects the site of infection

Nonspecific

Can be shared by a number of diverse infectious diseases

Obvious

Predictable patterns

Covert

May require laboratory testing to detect

incubation period

Time period between exposure to pathogen and symptom development

prodomal stage

initial appearance of symptoms

Acute stage

rapid proliferation of microbe --\> maximum impact of infectious process for host

Convalescent stage

containment of infection, elimination of pathogen, symptom resolution, tissue repair

Resolution

Total elimination of microbe without residual signs or symptoms of disease

Toxins

Substance that alter or destroy normal function of host or host's cells

Bacterial endotoxins

Lipopolysaccharides found in cell wall of gram-negative bacteria

Bacterial exotoxins

Proteins released from bacterial cell during growth

Adhesion factors

allow microbe to attach to and colonize host

Evasion factors

Help microbe evade immune system

Invasion factors

facilitate the penetration of anatomical barriers and cause damage to host tissues

Culture

Growth of the microorganism

Techniques for laboratory diagnosis of an infectious agent

Culture

Serology detection of characteristic antigens

DNA and RNA sequencing

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Types of antimicrobial agents

Antibacterial agents. Antiviral agents. Antifungal agents. Antiparasitic agents.

Antiviral agents

Stop viral replication

Antifungal agents

Target cytoplasmic membranes of yeasts or molds

Antiparasitic agents

Target parasites metabolism or cellular anatomy not shared by host