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Summary of Chapter 14 of MBY 161
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A well-written summary of chapter 14 of MBY 161. The principles of disease and epidemiology.
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Chapter 14: Principles of disease andepidemiology
pathogens--- disease causing organism
o there is a delicate balance
When our defenses resist these pathogenic capabilities, we maintain
our health—when the pathogen’s capabilities overcome our defenses,
disease results
community acquired infections--- infection contracted outside the
health care setting
Pathology, infection and disease
Pathology—the scientific study of disease
o pathos = suffering; logos = science)
o Pathology is first concerned with the cause, or etiology, of disease. Second, it
deals with pathogenesis, the manner in which a disease develops. Third,
pathology is concerned with the structural and functional changes brought
about by disease and their effects on the body
etiology--- study of the cause of disease
pathogenesis—the manner in which a disease develops
infection—the growth of microbes in the body or the presence of a
particular type of microbe where it is not normally found is also an
infection
disease--- an abnormal state in which part or all of the body is not
properly adjusted or is incapable of performing normal functions; any
change from a state of health
Few microorganisms are pathogenic. In fact, the presence of some
microorganisms can even benefit the host
Human microbiome
Recent research indicates that normal and characteristic microbial populations begin
to establish themselves in an individual before birth (in utero).
More microorganisms are introduced to the newborn’s body from the environment
when breathing and feeding start. An individual’s microbiome changes rapidly during
the first three years as the personal microbiome becomes established
After birth, E. coli and other bacteria acquired from foods, people, and pets begin to
inhabit the large intestine.
These microorganisms remain there throughout life and, in response to altered
environmental conditions, may increase or decrease in number and contribute to
health and disease.
Human Microbiome Project--- a project to characterize the microbial communities
found on the human body
, o Its goal is to determine the relationship between changes in the human
microbiome and human health and disease.
o normal microbiata--- the microorganisms that colonize a host without
causing disease; also called normal flora
o transient microbiota—the microorganisms that are present in an animal for a
short time without causing a disease
o many factors determine the distribution and composition of the normal
microbiota
nutrients, physical and chemical factors, the host’s defenses, and
mechanical factors
microbes can only colonize in sites that can supply the appropriate
nutrients
these nutrients can be derived from
o dead cells, food in the gastrointestinal tract, secretory
and excretory products of cells, and substances in body
fluids.
factors affect the growth and composition of microbes
temperature, pH, available oxygen and carbon dioxide, salinity,
and sunlight.
defenses against microbes
variety of molecules and activated cells that kill microbes,
inhibit their growth, prevent their adhesion to host cell surfaces,
and neutralize toxins that microbes produce.
hygiene hypothesis
Childhood exposure to microorganisms helps the immune
system develop. Indeed, it has been proposed that insufficient
exposure to microorganisms in childhood may interfere with
the development of the immune system and may play a role in
increasing rates of allergies and other immune disorders.
mechanical forces may affect the colonization of microbiota
chewing, coughing, sneezing, urinating
factors that influence the normal microbiota
age, nutritional status, diet, health status, disability,
hospitalization, stress, climate, geography, personal hygiene,
living conditions, occupation, and lifestyle.
Relantionships between the normal microbiota and the host
o competitive exclusion/microbial antagonism--- growth of some microbes
prevents the growth of other microbes
Once established, the normal microbiota can benefit the host by
preventing the overgrowth of harmful microorganisms.
it involves competition among microbes
One consequence of this competition is that the normal
microbiota protect the host against colonization by potentially
pathogenic microbes by competing for nutrients, producing
substances harmful to the invading microbes, and affecting
conditions such as pH and available oxygen
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