5.2 - Intro to Infectious Disease Flashcards
What is an infectious disease?
Illness caused by a specific infectious agent or its toxic product that results from transmission of that agent or its product from an infected person, animal or reservoir to a susceptible host, either directly or indirectly through an intermediate plant of animal host vector or inanimate environment
Differentiate between infectious agents
Prions: only a protein, no nucleic acid, non-living
Viruses: RNA/DNA, protein coat and maybe lipid bilayer/envelope, non-living
Bacteria: prokaryotic single cell living organism. No organelles, nucleus or nuclear envelope
Fungi: eukaryotic, exists as molds or yeasts
Parasites:
Protozoans: eukaryotic, unicellular parasites
Helminthes: multicellular eukaryotic parasites
Ectoparasites: lice, usually arthropods that live on the skin
Obligate pathogens
can cause disease in virtually any susceptible host including normal, health hosts with intact immune systems. Known as true pathogens
Opportunistic pathogens
Potentially infectious agents that rarely cause disease in individuals with healthy immune systems
Usually cause disease in people with compromised immune systems due to age, genetic defects, medical procedures
Symbiotic relationships
Commensalism: shelter and food
Mutualism: reciprocal benefit
Parasitism: unilateral benefit
What are Koch’s postulates?
Organism must be isolated from every patient with the disease
Organism must be isolated free from all other organisms and grown in pure culture in vitro
Pure organism must cause the disease in a healthy, susceptible animal
Organism must be recovered from the inoculated animal
What is a reservoir?
Reservoir: where the microbe in normally before infecting a susceptible persion
How do you break the chain of infection?
Prevention and control measure for human reservoirs
Diagnosis and treatment, screening, isolation and reporting
Prevention and control measures for animal reservoir
Vaccination, treatment and euthanasia
Prevention measures of susceptible hosts
Vaccination, chemoprophylaxis, maintain a healthy lifestyle and limiting exposure to reservoir of infection
Natural history of infection
Incubation period (no signs or symptoms) Prodromal period (vague, general symptoms)
Illness (most severe signs and symptoms)
Decline (declining signs and symptoms)
Convalescence (no signs or symptoms)
Six basic processes of microbial pathogenesis
Microbial encounter with and entry into the host
Microbial adherence: a potential pathogen must anchor itself to a tissue or tissue factor using adhesins, unless directly inoculated into the bloodstream
HIV uses viral and cellular proteins
Bacteria also use adhesins
Microbial growth after entry
Viruses are obligate intracellular parasites. Must generate new progeny inside a host cell
Avoidance of innate host defenses
Tissue invasion and tropism
Tissue damage and disease
Transmission to new hosts
What issues arise with Koch postulates?
What if the pathogen is found in healthy asymptomatic patients?
What if multiple pathogens cause the same disease?
What if the pathogen cannot be cultured?
What if there is no good animal model?
What if the pathogen does not cause disease in all subjects?
What is a zoonosis?
A disease that rises from an animal vector
What is a formit?
Bacteria that can be transmited via a nonliving surface in the enviroment.
Example: doorknob, water fountain, etc
What are exits from the chain of infection?
Exits from human reservoir
Exit: can be from a human or non-human reservior Exit from non-human reservior: Pets, insects, animals, food, inanimate object
What are the three types of transmission?
Direct, indirect, and vertical
What are direct methods of transmission?
Direct modes of transmission: direct physical contact with blood or body fluids
Person to person transmission. Touching, respiratory droplets, sexual intercourse, talking, or sneezing
What are examples of vertical transmission?
Vertical transmission: mother to infant