14 Flashcards
pathogen
Any parasite
that causes disease is called a pathogen
axenic
sites that are free of any microbes
Your normal microbiota began to develop when
your surrounding
amniotic membrane ruptured and microorganisms
came in contact with you during birth.
reservoirs
Sites where pathogens
are maintained as a source of infection are called reservoirs of
infection.
zoonoses
Diseases that spread
naturally from their usual animal hosts to humans
zoonoses most likely type to be transmitted
back to animal hosts.
Zoonotic diseases transmitted via the bites of bloodsucking
arthropods
contamination
the mere presence of microbes
in or on the body.
infection
some microbial contminannts overcome
the body’s external defenses, multiply, and become established
in the body; such a successful invasion of the body by a
pathogen is called an infection.
portals of entry
skin, mucous membrane, placenta | parenteral route
most frequently used portal of
entry.
respiratory tract
adhesion
After entering the body, symbionts must adhere to cells if they
are to be successful in establishing colonies. The process by which
microorganisms attach themselves to cells
adhesion factors
To accomplish adhesion, pathogens
use adhesion factors, which are either specialized structures or attachment proteins
ligands
viruses and many bacteria
have surface lipoprotein and glycoprotein molecules called ligands
that enable them to bind to complementary receptors on host cells
(Figure 14.5). Ligands are also called adhesins on bacteria and attachment
proteins on viruses.
ligand receptor molecules
Receptor molecules
on host cells are typically glycoproteins containing sugar molecules
such as mannose and galactose.
avirulent
Bacterial cells and viruses that
have lost the ability to make ligands—whether as the result of
some genetic change (mutation) or exposure to certain physical
or chemical agents (as occurs in the production of some
vaccines)—become harmless, or avirulent
biofilm
Some bacterial pathogens do not attach to host cells directly
but instead interact with each other to form a sticky web of bacteria
and polysaccharides called a biofilm, which adheres to a
surface within a host.
symptoms
subjective characteristics of a disease that can be felt by
the patient alone
signs
objective manifestations
of disease that can be observed or measured by others
syndrome
a group of symptoms and signs that collectively
characterizes a particular disease or abnormal condition
subclinical
asymptomatic infections
congenital
diseases that are present at birth
etiology
study of the cause of a disease
Using his postulates, Koch proved that
Bacillus
anthracis causes anthrax and
TB
germ theory of disease
Louis Pasteur,
Robert Koch, and other microbiologists proposed the germ
theory of disease, which states that disease is caused by infections
of pathogenic microorganisms
kochs postulates
1 The suspected agent (bacterium, virus, etc.) must be present
in every case of the disease.
2 That agent must be isolated and grown in pure culture.
3 The cultured agent must cause the disease when it is inoculated
into a healthy, susceptible experimental host.
4 The same agent mus
pathogenicity
The ability of a microorganism
to cause disease is termed pathogenicity
virulence
degree of pathogenicity. In other
words, virulence is the relative ability of a pathogen to infect a
host and cause disease. NOT severity of disease
xtracellular enzymes
Many pathogens secrete enzymes that enable them to dissolve
structural chemicals in the body and thereby maintain
an infection, invade further, and avoid body defenses.
toxins
Toxins are chemicals that either harm tissues or trigger host
immune responses that cause damage.
toxemia
toxins enter the bloodstream and are carried to other parts of
the body, including sites that may be far removed from the
site of infection.
exotoxins
Many microorganisms secrete exotoxins that are
central to their pathogenicity in that they destroy host cells or
interfere with host metabolism. Exotoxins are of three principal
types: cyto, neuro, enterotoxins
antitoxins
protective
molecules called antibodies that bind to specific toxins and
neutralize them.
endotoxin
Gram-negative bacteria have an outer (wall) membrane
composed of lipopolysaccharide, phospholipids, and
proteins (see Figure 3.14). Endotoxin, also called lipid A, is
the lipid portion of the membrane’s lipopolysaccharide.
Endotoxin can be released when
Gram-negative bacteria
divide, die naturally, or are digested by phagocytic cells
such as macrophages
endotoxin stimulates
Many types of lipid
A stimulate the body to release chemicals that cause fever, inflammation,
diarrhea, hemorrhaging, shock, and blood coagulation.
capsules
The capsules of many pathogenic bacteria (see
Figure 3.5a) are effective virulence factors because many capsules
are composed of chemicals normally found in the body
(including polysaccharides); as a result, they do not stimulate
a host’s immune response.
- Additionally, capsules are often slippery, making it difficult for
phagocytes to surround and phagocytize them—their pseudopods
cannot grip the capsule
antiphagocytic chemicals
Some bacteria, including the cause
of gonorrhea, produce chemicals that prevent the fusion of lysosomes
with phagocytic vesicles, allowing the bacteria to survive
inside phagocytes
disease process
IPIDC
incubation period, a prodromal
period, illness, decline, and convalescence
incubation period
The incubation period is the time between infection and occurrence
of the first symptoms or signs of disease.
prodromal period
a short time of generalized, mild symptoms (such as malaise and muscle aches) that precedes illness. Not all infectious diseases have a prodromal stage.
illness
Illness is the most severe stage of an infectious disease. Signs
and symptoms are most evident during this time. Typically the
patient’s immune system has not yet fully responded to the pathogens, and their presence is harming the body. This stage is
usually when a physician first sees the patient.
decline
During the period of decline, the body gradually returns to
normal as the patient’s immune response and/or medical treatment
vanquish the pathogens. Fever and other signs and symptoms
subside. Normally the immune response and its products
(such as antibodies in the blood) peak during this stage. I
convalescence
During convalescence (kon@vaI@les´ens), the patient recovers from the illness; tissues are repaired and returned to normal.
contact trans
Contact transmission is the spread of pathogens from one host to
another by direct contact, indirect contact, or respiratory droplets.
direct contact trans
Direct contact transmission, including person-to-person
spread, typically involves body contact between hosts. Touching,
kissing, and sexual intercourse, across placenta
indirect contact trans
when pathogens are
spread from one host to another by fomites (fom´i@tez; singular:
fomes, fo´mez), which are inanimate objects that are inadvertently
used to transfer pathogens to new hosts.
- needles, toothbrushes, paper tissues, toys, money, diapers,
drinking glasses,
droplet trans
Droplet transmission is a third type of contact transmission.
Pathogens can be transmitted within droplet nuclei (droplets
of mucus) that exit the body during exhaling, coughing,
and sneezing
vehicle trans
the spread of pathogens via air, drinking
water, and food, as well as bodily fluids being handled outside
the body.
airborne trans
Airborne transmission involves the spread of pathogens
farther than 1 meter to the respiratory mucous membranes of
a new host via an aerosol (ar´o@sol)—a cloud of small droplets
and solid particles suspended in the air. Aerosols may contain
pathogens either on dust or inside droplets.
waterborne trans
important in the spread of
many gastrointestinal diseases
fecal oral infection
some waterborne pathogens r shed in feces, enter through the gastrointestinal mucous membrane or skin, and
subsequently can cause disease elsewhere in the body.
vectors
Vectors are animals that transmit diseases from one host to another.
Vectors can be either biological or mechanical.
biological vectors
Biological vectors not only transmit pathogens but also
serve as hosts for the multiplication of a pathogen during
some stage of the pathogen’s life cycle.
mechanical vectors
Mechanical vectors are not required as hosts by the pathogens
they transmit; such vectors only passively carry pathogens
to new hosts on their feet or other body parts.
latent diseases
Latent diseases are those in
which a pathogen remains inactive for a long period of time before
becoming active.
communicable disease
When an infectious disease comes from another infected
host, either directly or indirectly,
contagious disease
If a communicable disease is easily transmitted
between hosts
epidemiology
the study of where and when diseases
occur and how they are transmitted within populations.
incidence
Incidence is the
number of new cases of a disease in a given area or population during a given period of time
prevalence
prevalence is the total number of
cases, both new and already existing, in a given area or population
during a given period of time. In other words, prevalence is
a cumulative number.
endemic
A disease that normally occurs continually (at
moderately regular intervals) at a relatively stable incidence
within a given population or geographical area is said to be
endemic11 to that population or region.
epidemic
Whenever a disease occurs at a greater
frequency than is usual for an area or population, the disease
is said to be epidemic within that area or population.
pandemic
If an epidemic occurs simultaneously on more than one
continent, it is referred to as a pandemic
descriptive epidemiology
- earliest: snow’s cholera study
- involves the careful tabulation of
data concerning a disease. Relevant information includes the
location and time of cases of the disease as well as information
about the patients, such as ages, gender, occupations, health
histories, and socioeconomic groups.
index case
1st case of disease in a given area/population
analytical epidemiolgoy
Analytical epidemiology investigates a disease in detail, including
analysis of data acquired in descriptive epidemiological
studies, to determine the probable cause, mode of transmission, and possible means of prevention of the disease.
experimental epidemiolgoy
Experimental epidemiology involves testing a hypothesis concerning
the cause of a disease.
nosocomial
acquired in healthcare settings
exogenous nosocomial infections
caused by pathogens acquired from
the health care environment.
endogenous nosocomial infections
opportunists cause endogenous nosocomial infections
(en@doj´eI@nuI s); that is, they arise from normal microbiota within
the patient that become pathogenic because of factors within the
health care setting
iatrogenic infections
a subset of nosocomial infections
that ironically are the direct result of modern medical
procedures such as the use of catheters, invasive diagnostic
procedures, and surgery.
superinfections
may result from the use of antimicrobial
drugs that, by inhibiting some resident microbiota, allow others
to thrive in the absence of competition.
species resistance
Because the cells and certain basic physiological processes of
humans are incompatible with those of most plant and animal
pathogens, humans have what is termed species resistance to
these pathogens.
innate immunity
The first
line of defense is composed chiefly of external physical barriers
to pathogens, especially the skin and mucous membranes. The
second line of defense is internal and is composed of protective
cells, bloodborne chemicals, and processes that inactivate or
kill invaders. Together, the first two lines of defense are called
innate immunity because they are present at birth prior to contact
with infectious agents or their products.
adaptive immunity
the body’s ability to recognize and then
mount a defense against distinct invaders and their products
epidermis
The epidermis is composed of multiple layers of tightly
packed cells. It constitutes a physical barrier to most bacteria,
fungi, and viruses. Very few pathogens can penetrate the layers
of epidermal cells unless the skin has been burned, broken, or cut.
The deepest cells of the epidermis continually divide, pushing
their daughter cells toward the surface.
dendritic cells
The epidermis also contains phagocytic cells called dendritic1
cells. The slender, fingerlike processes of dendritic cells
extend among the surrounding cells, forming an almost continuous
network to intercept invaders. Dendritic cells both phagocytize
pathogens nonspecifically and play a role in adaptive
immunity
