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MICROPARA
Session 10
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Pathology
The study of
disease
Etiology
The study of the cause of a
disease
Pathogenesis
The
development
of disease
Pathogen
Have special
properties
that allow them to invade the human body or produce
toxins
Infection
Colonization of the body by
pathogens
Disease
An
abnormal
state in which the body is not functioning
normally
Normal
Microbiota
(Flora)
Microbial Antagonism
due to
competition
between microbes
Resident
Flora (normal) acquired at passage through
birth canal
Resident Flora (normal)
Establish
permanent
colonies on/inside body without producing
disease
Protect the host by occupying
niches
that pathogens might occupy (
Competitive exclusion
)
Protect the host by producing
acids
Protect the host by producing
bacteriocins
Protect the host by stimulation of
immune system
Protective role of Resident Flora
Prevent pathogens
from attaching
Consume available
nutrients
Produce
toxic
compounds that
inhibit
other microbes
Transient Microbiota (Flora)
Certain
microbes
are present for various periods (days, weeks, or months) – then
disappears
Probiotics
Live microbes applied to or ingested into the body, intended to exert a
beneficial
effect
Dynamic nature of resident flora: changes due to
age
, type of food consumed, Hormonal state,
antibiotics
Various Co-existence Relationships Between Bacteria and Host
Symbiosis
Mutualism
Commensalism
Parasitism
Opportunistic
pathogens
Cause disease under special conditions (
mutualistic
relationship becomes
parasitic
)
Healthy carriers of
pathogenic
organisms
Cooperation
among
microorganisms
: One microorganism may make it possible for another to cause disease or produce more severe symptoms
Koch's Postulates: Proof of Etiology of Infectious Diseases
The same pathogen must be present in every case of the disease
The pathogen must be
isolated
from the diseased host and grown in
pure culture
The pathogen from the pure culture must cause the disease when it is
inoculated
into a
healthy
, susceptible lab animal
The pathogen must be
isolated
from the inoculated animal and must be shown to be the
original
microbe
Exceptions to Koch's Postulates
To establish disease etiology for
viruses
and
bacteria
, which cannot be grown on artificial media
Some diseases, e.g.: pneumonia and nephritis, may be caused by a variety of
microbes
Some pathogens, such as
S. pyogenes
, cause several different diseases
Certain pathogens, such as
HIV
, cause disease in humans only
Symptom
A change in body function that is felt by a patient as a result of
disease
Sign
A
change
in a body that can be measured or observed as a result of
disease
Syndrome
A specific group of signs and symptoms that accompany a
disease
Communicable vs. Non-communicable vs. Contagious
Communicable disease: A disease that is
spread
from one host to
another
Contagious disease: A disease that is
easily
spread from one host to another
Noncommunicable disease: A disease that is not transmitted from one host to another
Incidence
Fraction of a population that contracts a
disease
during a specific
time
Prevalence
Fraction of a population having a specific
disease
at a given time
Occurrence of a Disease
Sporadic
disease: Disease that occurs occasionally in a population
Endemic
disease: Disease constantly present in a population
Epidemic
disease: Disease acquired by many hosts in a given area in a short time
Pandemic
disease: Worldwide epidemic
Severity or Duration of a Disease
Acute
: Disease develops
rapidly
Chronic
: Disease develops
slowly
Subacute
: Symptoms between acute and
chronic
Latent
: Disease with a period of no symptoms when the causative agent is
inactive
Herd immunity
Presence of
immunity
to a
disease
in most of the population
Extent of Host Involvement
Toxemia
: Toxins in the blood
Viremia
: Viruses in the blood
Primary
infection: Acute infection that causes the initial illness
Secondary
infection: Opportunistic infection after a primary (predisposing) infection
Subclinical
disease: No noticeable signs or symptoms (inapparent infection)
Types of Infection
Local
: limited to small area of body
Systemic
: spread throughout body via_
Focal
: spread from local infection to specific areas
Primary
: acute infection causing initial illness
Secondary
: occurs after host is weakened from primary infection
Subclinical
(inapparent): no noticeable signs and symptoms
Patterns of Disease: Predisposing Factors
Genetics
Gender
Climate
and weather
Age
Stress
and
fatigue
Lifestyle
Chemotherapy
Coronaviruses are a large family of viruses, some of which can
infect
people
Mild illness
(common colds) and severe, or even fatal, disease - such as
Middle East Respiratory Syndrome Coronavirus
(MERS-CoV) and SARS
The
natural reservoir
for coronaviruses is thought to be
animal
hosts
New strains emerge from this
reservoir
, infect an 'intermediate' host, and from there
infect
people
Some coronaviruses are efficient at
human-to-human
transmission, while others are
not
Coronaviruses
are common in many different species of animals, including
camels
, cattle, cats, and bats
The
2019-novel
coronavirus (
2019-nCoV
) is a previously-unidentified strain of coronavirus
Symptoms of 2019-nCoV
fever
cough
shortness
of
breath
difficulty breathing
2019-nCoV
is capable of causing severe illness, and some
infected
people have died
It is possible that people with
underlying
health conditions are at
higher
risk for severe disease
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