Principles of Disease Flashcards
all interactions of one species with one another
symbiosis
often used to identify mutualisms
symbiosis
Both organisms benefit from interaction
mutualisms
One organism benefits and the other is
neither harmed nor helped
commensalism
Organism that benefits
commensal
example of commensalism
Surface microbes on plants or
animals
One organism gains and the other is harmed
parasitism
Often difficult to distinguish from predation
Can be used as a form of biological control
parasitism
microorganisms found growing on body
surfaces of healthy individuals; permanently colonize the host
Normal Microbiota
what does normal microbiota protect through
competitive exclusion
Sites of Colonization by Normal Flora
eyes, mouth, skin, large intestine, and urinary and reproductive systems
The addition of microbes to the diet in order to provide health benefits beyond the basic nutritional value
probiotics
non-digestible food ingredient that beneficially affects the host
prebiotics
Oligosaccharide polymers that
are not processed until they
enter large intestine
prebiotics
Combination of prebiotics and
probiotics in single supplement
Synbiotic System
limits colonization of gut by the process of
competitive exclusion
PREEMPT(benefit of probiotics)
Colonization of the body by pathogens
infection
impairment of the normal state of an organism or any of its components that hinders the performance of vital functions
disease
Disease that is caused by microorganisms
Infectious disease
A disease that is not
transmitted from one host to another
Noncommunicable disease
A disease that is spread from one host to another
Communicable disease
A disease that is easily spread
from one host to another
Contagious disease
A change in body function that is felt by a
patient as a result of disease
symptom
A change in a body that can be measured or
observed as a result of disease
sign
A specific group of signs and symptoms that
accompany a disease
syndrome
Usually short in duration
Host may develop long-lasting immunity
Result in productive infections
Acute Infections
Viruses (pathogen) continually present in host
Can be divided into three categories
Persistent Infections
three categories of persistent infections
latent, chronic, and slow
Infection is followed by symptomless period,
Virus stops reproducing and remains dormant for some time
symptoms, antivirus-antibodies, and viruses are not detectable
Latent infections
Infectious particles are again detected
reactivation
examples of reactivation/latency
Herpes simplex viruses (cold sores)
Shingles (zoster)
Infectious agent can be detected at all times
Disease may be present or absent during extended
times or may develop late
chronic
example of chronic infection
Hepatitis C
Infectious agent gradually increases in amount over long period of time
slow infections
Two groups of infectious agents cause slow infections
Lentiviruses (retroviruses) which include HIV
and Prions
occurs occasionally in a population (or at irregular
intervals)
Sporadic disease
sudden, unexpected occurrence of disease
usually focal or in a limited segment of population
outbreak
constantly present in a population
endemic
acquired by many hosts in a given area
in a short time
epidemic
Increase in disease occurrence within large
population over wide region (usually worldwide)
pandemic
Fraction of a population that contracts a
disease during a specific time
incidence
Fraction of a population having a specific
disease at a given time
prevalence
Mapped the occurrence of
cholera in London 1848
John Snow
Showed that handwashing
decreased the incidence of
puerperal fever 1846
Ignaz Semmelweis
Showed that improved sanitation
decreased the incidence of
epidemic typhus 1858
Florence Nightingale
plays important role in isolation and identification of
pathogen
Clinical microbiology lab
location from which pathogen is immediately
transmitted to host
source
site or natural environmental location in which
pathogen normally resides
sometimes functions as source of pathogen
reservoir
the important animate
sources of the pathogen
human hosts
(infected host)
carriers
harbors pathogen a short time
casual carrier
harbors pathogen for long periods of time
chronic carrier
harbors pathogen but is not yet ill
incubatory carrier
has overt clinical case of disease
active carrier
has recovered from disease but continues to
harbor large numbers of pathogen
convalescent carrier
harbors pathogen but is not ill
healthy carrier
Sources/Reservoirs
animal, water, air, soil, and food
Four main routes of pathogen transmission
Contact
Airborne
Vehicle
vector-borne
coming together or touching of
source/reservoir and host
contact transmission
intermediate contact
common objects such as tissues, bedding, eating
utensils, toys, books
fomites
inanimate materials or objects involved in
pathogen transmission
single vehicle spreads pathogen to multiple hosts
e.g., water and food
vehicle transmission
passive carriage of pathogen on body of vector
no growth of pathogen during transmission
external transmission
carried within vector
internal transmission
pathogen does not undergo changes
within vector
harborage transmission
pathogen undergoes changes within vector
biologic transmission
two main factors of host susceptibility
defense mechanisms of host
pathogenicity of pathogen
movement of pathogen to portal of exit
Example: parasitic helminths
active escape
excretion in feces, urine, droplets, saliva, or
desquamated cells
Mode most frequently used by microoganisms
passive escape
first step in controlling epidemics
Reduce or eliminate source or reservoir of infection
second step in controlling epidemics
Break connection between source and susceptible
individual
third step in controlling epidemics
Reduce number of susceptible individuals (raise the
level of herd immunity
acquired due to hospital stay
affects 5-15 % of hospital patients
nosocomial infections
