Important words and
concepts from Chapter 14, Black, 1999 (3/28/2003):
by Stephen T. Abedon (abedon.1@osu.edu)
for Micro 509
at the Ohio State University
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Course-external links are
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(1)
Chapter title: Host-Microbe Relationships and Disease Processes
(a)
"Pathogens
have certain invasive capabilities, and you have a variety of defenses."
(b)
[host-microbe relationships and
disease processes (Google Search)] [index]
TYPES OF SYMBIOSES
(a)
A
symbiosis is when two organisms live intimately close, typically over longer
periods, often measured in generations for at least one of the organisms
(b)
If
one organism is substantially larger than the other organism, such that the
smaller organism lives in or on the other, then the larger organism is referred
to as a host and the smaller as a symbiont
(c)
Symbioses
are classified in terms of the benefits or costs accrued by the host in the
course of the symbiosis (in general we assume that symbiont gains from the
interaction)
(i)
Mutualism
(ii)
Parasitism
(iii)
Commensalism
(d)
[symbiosis and microbiology
(Google Search)]
[index]
(a)
A
symbiosis in which both host and symbiont benefit
(b)
For
example, in the mitochondrial-eukaryote endosymbiosis the mitochondria benefits
with a home, protection, provisioning of nutrients, and dissemination of
progeny mitochondria; the host benefits from cellular respiration (plus
additional biochemical tricks)
(c)
Other
mutualistic relationships abound including between hosts and otherwise
free-living microorganisms
(d)
[mutualism and microbiology
(Google Search)]
[biodiversity and mutualism in
ecosystems] [modeling mutualism]
[coevolution (and mutualism)]
[marine mutualisms] [index]
(a)
A
Commensalism is a symbiosis in which one of the participants
(typically the symbiont) benefits but the other organism (typically the host)
neither benefits nor is harmed
(b)
Due
to the complex nature of symbiosis it is often difficult to describe costs and
benefits with sufficient accuracy to make it possible to state with reasonable
certainty that a host neither benefits nor is harmed by its symbiont
(c)
Consequently,
commensalism is perhaps a rarely realized ideal
(d)
Nevertheless,
in the absence of evidence that a symbiont either hurts or helps its host, the
relationship is assumed to be one of commensalism
(e)
The
majority of the organisms living in or on your body probably
represent commensals, though this designation might require a consideration of microbial competition (a.k.a., microbial antagonism)
as something other than a benefit provided by the symbiont to the host
(f)
[commensalism and microbiology
(Google Search)]
[commensalism] [index]
(5)
Microbial competition (microbial antagonism)
(a)
A
microbe that fails to harm its host under ordinary circumstances and also does
not overtly help its host may still provide a helpful service to its host
(regardless, the symbiont gains by having a place to live as well as nutrients
found on or in the body)
(b)
This
is because such an organism is existing within a niche/location on or in the
host; the filling of any niche/location by a not-harmful bacterium serves to
prevent the filling of the same niche/location by a harmful bacterium
(c)
This
prevention of harmful bacterial growth by a non-harmful bacterium is called
microbial competition or microbial antagonism
(d)
(In
my opinion, it is a matter of semantics whether microbial competition makes a
symbiotic relationship a mutual one; that is, some argue that a
microbe has to live somewhere and therefore any effect such a microbe has on
preventing the growth of pathogens simply by filling this space/niche does not
constitute a direct benefit to the host—instead it is an indirect benefit—and
therefore the symbiotic relationship between host and a harmless microbe—that
is effecting microbial antagonism is a commensal one)
(e)
[microbial antagonism,
microbial competition
(Google Search)]
[index]
(a)
The
third category of symbioses is one where the host is harmed while the symbiont
gains (the latter, e.g., by having a place to live and something to eat)
(b)
Using
the term parasitism in terms of a symbiosis includes many pathogens (indeed,
all) including pathogenic bacteria, viruses, fungi, protozoa, helminths, and
arthropods
(c)
Note
that a more-narrow definition of parasite includes
only the latter three categories (protozoa, helminthes, and arthropods)
(d)
"Parasitism
encompasses a wide rage of relationships, from those in which the host sustains
only slight harm to those in which the host is killed. Some parasites obtain
comfortable living arrangements by causing only modest harm to their host.
Other parasites kill their hosts, thereby rendering themselves homeless."
(e)
[parasitism and microbiology
(Google Search)]
[parasitism] [index]
INFECTIOUS DISEASE
(a)
"Disease
is a disturbance in the state of health (of the host) wherein the body cannot
carry out all its normal functions… When an infection causes
disease, the effects of the disease range from mild to severe… Disease, or
illness, is characterized by changes in the host that interfere with normal function."
(b)
[definition disease
(Google Search)]
[index]
(8)
How microbes cause disease
(a)
"Microorganisms
act in certain ways that allow them to cause disease. These
actions include gaining access to the host,
adhering
to and colonizing cell surfaces, invading tissues,
and producing toxins and other harmful metabolic products. However, host
defense mechanisms tend to thwart the actions of microorganisms. The occurrence
of a disease depends on whether the pathogen or the host wins the battle; if it
is a draw, a chronic, long-lasting disease may result."
(emphasis mine)
(b)
[how microbes cause disease
(Google Search)]
[index]
(a)
Contamination
is the converse of sterility, i.e., an environment that is
not sterile is one that is contaminated with microorganisms
(b)
Contamination
is the first step toward the occurrence of infectious disease,
i.e., a organism must be present (in the wrong place and at the wrong time as
far as the host is concerned) to start down a path leading to disease
(c)
Note,
however, that just because something is contaminated with a microorganism
(including contamination of yourself) does not mean that disease is occurring
or will occur
(d)
[microbe contamination,
microbial contamination,
bacterial contamination
(Google Search)]
[index]
(a)
Upping
the ante in terms of progression towards disease is
infection, the actual growth of an organism, particularly a pathogenic one, on
or within a host
(b)
Infection
can lead to disease (particularly if we define infection as a property solely
of pathogenic microorganisms) but does not necessarily do so since hosts
actively attempt to prevent the progression of infection to disease (see non-specific
host defences & host systems, basic principles of specific
immunity & immunization) [non-specific defenses of the
host] [humoral immunity]
(c)
So
long as a pathogen is prevented from invading tissues
(either by itself or with its toxins) disease may not occur (compare colonization
and invasion,
below)
(d)
[microbe infection, microbial infection,
bacterial infection,
viral infection (Google Search)] [index]
(a)
Pathogenicity
is an organism's capacity to cause disease; that is, whether or not it can
cause disease
(b)
Note
that this capacity is typically context dependent:
(i)
Pathogenicity
is higher in some environments (e.g., infection of the blood) than others
(e.g., presence in the lumen of the gastrointestinal tract), or
(ii)
Pathogenicity
is higher on some hosts but not on others depending on host susceptibility (in
general or specifically towards a particular pathogen)
(c)
Pathogenicity
can also depend on the number of organisms present, where many organisms have a
greater potential of bypassing host defenses than fewer organisms of the same
kind
(d)
A
commensal, more or less by definition at a given place and given time, has a
pathogenicity of effectively zero
(e)
For
an organism to be pathogenic it must be able to invade a host, multiply
in the host, evade host defenses, and harm the host in some way
(f)
[definition pathogenicity,
pathogenicity, capacity to cause disease
(Google Search)]
[index]
(a)
Virulence
is the degree of disease an organism has the potential to cause
(b)
That
is, a highly virulent pathogen can cause significant disease whereas an
avirulent microorganism can cause little or no disease
(c)
The
terms pathogenicity and virulence are closely related with (i)
pathogenicity referring to an organism’s binary ability to cause disease (or
not) given specific circumstances and (ii) virulence referring to the degree of
disease caused (also dependent on specific circumstances)
(d)
Evolution
of pathogen virulence:
(i)
The
virulence of a pathogen tends to increase (evolutionarily) when new hosts are
readily available (think childbirth fever in the days of Semmelweis)
(ii)
The
virulence of a pathogen tends to decline (evolutionarily) when new hosts are
difficult to acquire (think sexually transmitted diseases where a very sick
person will tend to not have sex and therefore not transmit the infection)
(iii)
Consider
this analogy: If you had access to a new car every day, at no cost to you, then
you would be less concerned about damaging one of those cars than when you are
responsible for and paying for the vehicle you drive; pathogens, too: if a
pathogen can be transmitted to a new host regardless of how much it damages
it’s current host, then there may be little selection against host damage,
a.k.a., host sickness, a.k.a., pathogen virulence (also, without a countering
force to select against virulence, i.e., few hosts available given disease, one
might expect selection for individual pathogens that reproduce the fastest
within the host environment, producing the most “baby” pathogens within the
infected host, and consequently, all else held constant, facilitating the most
host damage)
(iv)
[the evolution and maintenance of virulence in
microparasites] [index]
(e)
[definition virulence,
virulence -factor -factors,
virulence factors (Google Search)]
[index]
(a)
Attenuation
is a decline in virulence imposed on a pathogen by growing the
pathogen under conditions that decrease its adaptation to growth on a given
host; this is often done by growth in tissue culture or in otherwise non-host
species
(b)
That
is, by increasing a pathogen’s adaptation to one condition (e.g., tissue
culture), the pathogen’s adaptation to another condition (e.g., us) may be
reduced
(c)
Attenuation
is often employed in the development of live vaccines (e.g., Sabin oral polio vaccine)
(d)
[virulence attenuation
(Google Search)]
[index]
INDIGENOUS MICROBIOTA
(14)
Normal (indigenous) microflora
(microbiota)
(a)
"An
adult human body consists of approximately 1013 (10 trillion)
eukaryotic cells. It harbors an additional 1014 (100 trillion)
prokaryotic and eukaryotic microorganisms on the skin surface, on mucous membranes,
and in the passageways of the digestive, respiratory, and reproductive
systems."
(b)
The
vast majority of those organisms do not cause disease except under special
circumstances (movement to different body sites or decline in immunity)
(c)
Such
microorganisms are collectively called normal microflora (as well as a variety
of other names listed in the heading to this section such as indigenous
microflora and normal microbiota)
(d)
Most
of these organisms are considered commensals
(e)
These
organisms may have more-or-less permanent
associations with their hosts or more transient
associations
(f)
See Table 14.1, Major normal
microflora (unless otherwise noted, bacteria) of the human body
(g)
See Figure 14.3, Locations
of resident microflora of the human body
(h)
[normal flora, normal microflora, normal microbiota, indigenous flora, indigenous microflora,
indigenous microbiota
(Google Search)]
[index]
(15)
Microbe-free regions of the
body
(a)
Note that normal microflora are not present on all
regions of the body and that, in fact, the majority of the body is microbe free
(except for the endosymbionts within our own cells) except under unusual (e.g.,
disease-state)
circumstances
(b)
In particular, all of the interior of the body is microbe free (i.e.,
all but the gastrointestinal tract and the lower regions of the urogenital
tract)
(c)
See Table 14.2, Body
tissues, organs, and fluids that are normally microbe-free
(a)
The
resident microflora are the more-or-less permanent members of normal microflora
(b)
[resident microflora
(Google Search)]
[index]
(a)
The
transient microflora are present only under unusual (i.e., not usual) circumstances and only transiently (hours to months)
(b)
[transient microflora
(Google Search)]
[index]
(a)
Opportunists
are members of the normal microflora that do not usually cause disease but can
be pathogenic under certain circumstances, i.e.,
(i)
Host
immunosuppression
(ii)
Transfer
to other parts of the body
(iii)
Elimination
of microbial antagonism
(b)
Among
opportunists are members of the genera Escherichia,
Enterobacter, and Serratia
(c)
[opportunistic pathogen
(Google Search)]
[index]
ASSIGNING CAUSE
(a)
The
means, or logic, by which a specific microorganism is classified as the cause
of a disease is called Koch postulates
(b)
There
are four of these postulates and generally all four postulates must be
satisfied before an organism is considered by Koch’s postulates to be the cause
of a disease
(c)
These
postulates include:
(i)
Evidence
that the causative agent is always present when the specific disease is present
(ii)
Successful
isolation of the causative agent in pure culture
(iii)
Ability
of pure-cultures of the organism to cause disease in a healthy organism
(iv)
Successful
isolation of the causative agent from the experimentally infected host (i.e.,
indication that replication of the presumptive causative agent has occurred
(d)
See Figure 14.4,
Demonstration that a bacterial disease satisfies Koch's postulates
(e)
Koch's
postulates are not foolproof and a number of complications can arise in
assigning a specific disease to a specific causative agent
(i)
There
may exist more than one cause of a specific disease
(ii)
It
might not be possible to grow the causative agent in pure culture
(iii)
There
might not exist a suitable experimental host
(iv)
The
disease might result from more than one causative agent acting in unison
(f)
[Koch's postulates (Google Search)] [Robert Koch (MicroDude)] [index]
KINDS OF DISEASE
(a)
Disease
may be classified in a number of ways, many of which we will subsequently
discuss, including:
(ii)
Communicable disease
(iii)
Noncommunicable disease
(iv)
Contagious disease
(a)
An
infectious disease, as opposed to a noninfectious disease, is a disease that
involves pathogen infection; any disease caused by a pathogen is
an infectious disease; any disease not caused by a pathogen is a non-infectious
disease
(b)
Note
that infectious diseases are often notable in that the causative agent is not
diluted with time, i.e., the disease process increases the prevalence of the
causative agent (i.e., the pathogen replicates at the expense of the host)
(c)
However,
not all infectious diseases are spread from host to host; additionally, not all
infectious diseases are associated with pathogen infection of the host (e.g., intoxications
can result from exposure to secreted toxin rather than the secreting organism)
(d)
[infectious diseases
(Google Search)]
[index]
(a)
A
communicable disease is an infectious disease
that may be passed from individual to individual (particularly when all
individuals involved are of the same species)
(b)
Yet,
not all infectious diseases are considered communicable
(c)
A
more narrow definition of communicable disease is one that is infectious during
the incubation or recovery (convalescence)
periods of a disease
(d)
[communicable diseases
(Google Search)]
[index]
(a)
A
noncommunicable disease is an infectious disease
that is not spread from individual to individual but instead is acquired from
an inanimate object or other species
(b)
Noncommunicable
infectious disease may be differentiated into three categories:
(i)
Infections
caused by opportunists arising from an individual’s own microflora
(ii)
Poisonings
following ingestion of secreted exotoxins
(iii)
Infections
acquired from organisms found in the environment (other than from individuals
of one's own species)
(c)
[noncommunicable diseases
(Google Search)]
[index]
(a)
A
communicable diseases that is easily passed from individual to
individual is said to be contagious
(b)
Yes,
not all communicable disease are considered contagious (though certainly all
contagious diseases are considered communicable)
(c)
[contagious diseases
(Google Search)]
[index]
ADDITIONAL CONCEPTS AND TERMS PERTAINING TO
INFECTIOUS DISEASE
(a)
A
syndrome is a combination of signs and symptoms that are
characteristic of a disease
(b)
[syndrome (Google Search)] [index]
(a)
A
symptom is a characteristic of a disease that can be felt (by the
individual with the disease) but cannot be measured by another individual
(b)
[symptom (Google Search)] [index]
(a)
A sign is a characteristic of a disease
that can be measured by another individual (e.g., nurse or doctor)
(b)
[sign and disease (Google Search)] [index]
(a)
Properties
of a pathogens that allow them to cause disease are termed
virulence factors
(b)
Virulence
factors may distinguish a pathogenic microorganism from otherwise identical
non-pathogenic microorganisms by allowing pathogens to invade, adhere to, and
colonize a host, and then harm the host
(c)
Pathogens
may harm the host by direct or indirect means
(d)
Virulence
factors include
(i)
Pili
and capsules (used in adhesion to hosts
and to prevent phagocytosis)
(ii)
Enzymes
(used to evade host defenses or to harm the host)
(iii)
Toxins
(used to either obtain nutrients from the host, to evade host defenses, or
indirect means that do not aid the pathogen in its growth and survival)
(e)
See Table 14.3, Examples of
adhesive virulence factors
(f)
[virulence factors (Google Search)] [index]
(a)
Following
contact with a host a crucial first step in an infection is adherence to the
host
(b)
Failure
to adhere to the host typically results in an inability to causes disease
as well as removal from the host
(c)
Typical
mechanisms of adherence are specific such that just as viruses may adhere to
some cells but not others, bacteria may adhere to some cells (or tissues) but
not to others
(d)
Typically,
the host employs mechanisms designed to thwart adhesion
(e)
[bacterial adherence,
microbial adherence
(Google Search)]
[index]
(a)
It
is not enough to adhere, disease typically
only occurs if pathogen replication also occurs (exceptions are intoxications)
(b)
Colonization
is the growth of bacteria that have adhered to epithelial tissues (e.g., skin,
mucous membranes, or the tissue covering organs)
(c)
Key
to understanding the difference between colonization and infection is that
colonization does not necessarily cause disease
(d)
[bacterial colonization,
microbial colonization
(Google Search)]
[colonization and invasion
(Microbiology Webbed Out)]
[index]
(a)
Unless
toxins are produced, or excessive numbers of organisms are present, colonization
will not produce excessive disease
(b)
Instead,
severe disease usually results from invasion
(c)
Invasion
is the growing of infections into tissues, i.e., through and then
beneath epithelial tissues
(d)
Invasion
is damaging both because epithelial tissue must be damaged to allow invasion to
occur and because invasion allows direct damage to underlying tissues
(e)
Invasion
can be also be associated with avoidance of host defenses (including hiding in
blood clots and hiding intracellularly within host cells)
(f)
See Figure 14.5, Enzymatic
virulence factors help bacteria invade tissues and evade host defenses
(g)
[bacterial invasion,
microbial invasion
(Google Search)]
[colonization and invasion
(Microbiology Webbed Out)]
[index]
TOXINS
(a)
Toxins
are substances produced, for example, by microorganisms, that are poisonous to
host organisms
(b)
Bacterial
toxins may be classified as either exotoxins or endotoxins
(c)
There
is a profound difference between these two types of toxins as we shall discuss
(d)
See Table 14.4, Properties
of toxins
(e)
[bacterial toxins, microbial toxins (Google Search)] [index]
(a)
Exotoxins
are produced predominantly (though not exclusively) by Gram-positive bacteria
(b)
Exotoxins
are soluble substances secreted by bacterial cells
(c)
Exotoxins
act by a variety of mechanisms and symptoms that result from exposure to an
exotoxin depend on the structure of the exotoxin one is exposed to
(d)
Some
exotoxins are enzymes, e.g., hemolysins that catalyze the lysis of red blood
cells
(e)
Other
exotoxins damage or destroy phagocytic cells that have engulfed an exotoxin
producer
(f)
Exotoxins
may be distinguished in terms of the specific tissues they act against, e.g., neurotoxins
and enterotoxins
(g)
See Table 14.5, Effects of
exotoxins
(h)
[exotoxins (Google Search)] [index]
(a)
Neurotoxins
are exotoxins
that act on nervous system tissue
(b)
Examples
of neurotoxins are the botulism and tetanus toxin, preventing muscle
contraction and muscle relaxation, respectively
(c)
[neurotoxins (Google Search)] [index]
(a)
Enterotoxins
are exotoxins
that act on tissues of the gastrointestinal tract
(b)
[enterotoxins (Google Search)] [index]
(a)
A
disease
caused by the ingestion of a toxin (i.e., as opposed to caused by the
ingestion of a toxin-producing bacteria) are called intoxications (an ingestion
of a toxin-producing bacteria is called an infection)
(b)
Food
poisonings are intoxications
(c)
Botulism
as well as Staphylococcus food
poisoning are examples of intoxications
(d)
[intoxication and toxins
(Google Search)]
[index]
(a)
Many
exotoxins
are antigenic, i.e., antibodies can be made to them
(b)
However,
typically exotoxins are produced in such small quantities that the host fails
to develop an immune response against them
(c)
A
way around this is to vaccinate using relatively large
quantities of inactivated toxins, i.e., no-longer-toxic toxins, that are still
antigenically intact
(d)
Such
inactivated toxins are termed toxoids
(e)
Toxoids
are typically produced by exposure to chemicals such as formaldehyde
(f)
Vaccines
that employ toxoids include the tetanus and diphtheria vaccines
(g)
[toxoids and toxins
(Google Search)]
[index]
(a)
Endotoxin
is the lipid A portion of LPS
(b)
Endotoxins
are associated with Gram-negative bacteria
(c)
Endotoxins
are weak except in large doses and produce similar effects independent on the
producing organism
(d)
Large
doses are especially a problem given Gram-negative septicemia
(e)
Endotoxins
cause damage that is a consequence of the body using endotoxins as a signal for
Gram-negative bacterial infections; excessive amounts of endotoxin cause the
body to overreact and damage itself
(f)
Endotoxins
typically are released following bacterial division or lysis
(g)
Antibiotics
that lyse Gram-negative bacteria can produce a toxemia that
increases symptoms rather than alleviating them
(h)
Symptoms
can include severely reduced blood pressure (endotoxic shock), fever, tissue
damage, and death
(i)
Gram-negative
septicemia is an acute, difficult to treat killer
(j)
There
is no such thing as an endotoxin toxoid nor a vaccine against endotoxin
(k)
[endotoxins (Google Search)] [index]
TYPES OF INFECTIOUS DISEASE
(a)
Infectious disease can be described as being
(i)
Acute,
chronic, subacute, latent, or as an inapparent (subclinical)
infection
(ii)
Local,
focal, or systemic
(iii)
Septicemia,
bacteremia,
viremia,
or toxemia
(iv)
A
primary infection, secondary infection,
superinfection, or a mixed infection
(b)
Summarized in Table 14.7,
Terms used to describe infections
(c)
(Note
that many of the general searches below, especially of the phrases/terms ending
with “infection”, are full of examples but can provide relatively few general
discussions)
(a)
An
acute infection develops rapidly but is soon over
(b)
For
example, food poisoning
(c)
[acute infections, acute infection (Google Search)] [acute inflammation]
[index]
(a)
A
chronic infection develops slowly and is not soon over
(b)
For
example, mycoses, tuberculosis, etc.
(c)
[chronic infections,
chronic infection (Google Search)] [index]
(a)
A
subacute infection is the gray zone between acute and chronic
(b)
[subacute infections,
subacute infection
(Google Search)]
[index]
(a)
A
latent infection is sign-less or symptom-less for a
long while before signs and symptoms appear (e.g., AIDS)
(b)
[latent infections, latent infection (Google Search)] [index]
(44)
Inapparent (subclinical) infection
(a)
An
inapparent infection that does not display signs or symptoms
or, at least, all of the signs typically associated with a given syndrome
(b)
Minimally
asymptomatic carriers of disease display inapparent infections
(c)
[inapparent infections,
inapparent infection,
subclinical infections,
subclinical infection
(Google Search)]
[index]
(a)
A
local infection is confined to a certain area (e.g., a pimple)
(b)
[local infections, local infection (Google Search)] [index]
(a)
A
focal infection begins as a local infection but then spreads beyond
the local area as a bacteremia, or toxemia
(b)
Note
that the term focal infection is commonly employed in dentistry referring to
the introduction of microorganisms, microbial waste products, or microbial
toxins into the blood from the mouth, particularly associated with mouth
infections (to some extent a controversial linkage) or following invasive
dental procedures
(c)
[focal infections, focal infection (Google Search)] [focal infections in dentistry (including a
389 reference bibliography)] [focal infections in dentistry
(portions of reviews)] [index]
(a)
A
systemic infection is spread throughout the body in the blood or lymph
(b)
[systemic infections,
systemic infection
(Google Search)]
[bacteremia, septicemia, and septic shock (a list of
references)] [index]
(a)
Septicemia
is the growth of bacteria in the blood (a.k.a., blood poisoning)
(b)
[septicemia (Google Search)] [index]
(a)
A
bacteremia is the presence, without multiplication, of bacteria in the blood
(b)
[bacteremia (Google Search)] [index]
(a)
A
viremia is the presence of virus in the blood (this would be in the acellular
portion of the blood; recall that viruses require cells to multiply and that
these cells are not necessarily blood cells)
(b)
[viremia (Google Search)] [index]
(a)
A
toxemia is the presence of toxins in the blood
(b)
[toxemia (Google Search)] [index]
(a)
A
primary infection is the infection of a not-currently infected
person
(b)
["primary infection"
-HIV (Google Search)]
[index]
(a)
A
secondary infection is an infection that quickly follows a primary infection
(b)
[“A
second infection that occurs during or after treatment of a primary infection.
It may result from the treatments or from alterations in the immune system.” (RealPittsburgh.com)]
(c)
["secondary infection"
(Google Search)]
[index]
(a)
A
superinfection is a secondary infection caused by the treatment of a primary infection (e.g., as in the superinfection by an
antibiotic-resistant organism following antibiotic treatment)
(b)
[superinfection (Google Search)] [index]
(a)
A
mixed infection is a syndrome that is caused by a combination of two
or more infections (i.e., different pathogens)
(b)
Mixed
infections are unusual; most diseases are caused by a single pathogen
(c)
[mixed infection (Google Search)] [index]
STAGES OF INFECTIOUS DISEASE
(56)
Stages of an infectious
disease
(a)
Infectious
diseases tend to occur in stages including (in typical order)
(ii)
Prodromal
phase (not typical)
(iii)
Invasive
phase
(iv)
Acme
(v)
Decline
phase
(vi)
Convalescence period
(vii)
Sequelae
(not typical)
(b)
See Figure 14.9, Stages in
the course of an infectious disease
(c)
See Table 14.8, Correlation
of signs and symptoms with tissue damage
(d)
[stages of an infectious
disease (Google Search)]
[index]
(a)
Once
an infection
has begun but prior to the occurrence of signs and symptoms
is the period of incubation
(b)
Incubation
periods vary with host and organism
(c)
An
individual may be able to spread the disease to others during the incubation
period (depending on type of pathogen)
(d)
If
host defenses are successful, an infection may disappear without progressing
beyond the incubation period
(e)
See Figure 14.10, Incubation
periods of selected infectious diseases
(f)
["incubation period"
and "infectious disease" (Google Search)] [index]
(a)
The
prodromal period is a time when symptoms (and signs) appear, but
full-blown illness has not-yet begun
(b)
Basically,
you are vaguely aware you are sick
(c)
Not
all diseases
have prodromal periods
(d)
If
host defenses are successful, an infection may disappear without progressing
beyond this vague feeling of being sick
(e)
["prodromal period"
and "infectious disease" (Google Search)] [index]
(59)
Invasive phase (period
of illness)
(a)
The
invasive phase (a.k.a., period of illness) is the phase during which the
typical signs
and symptoms
of the disease are apparent
(b)
The
host at this point is doing its best to fight off the disease
(c)
Given
unsuccessful host defenses, the invasive phase can progress to death
(d)
[invasive phase, "period of illness"
and "infectious disease" (Google Search)] [index]
(a)
The
acme is the peak of disease symptoms (and signs)
(b)
The
occurrence of an acme results either from the infection being
self-limiting, or the host immune system or medical procedures bringing the
infection under control
(c)
[acme and "infectious
disease" (Google Search)] [index]
(a)
This
is the period during which symptoms (and signs) decrease as
the infection
is brought further under control
(b)
["decline phase" and
disease (Google Search)]
[index]
(a)
This
is the time during which the host repairs the damage wrought by the infection
(b)
Individuals
are not necessarily, depending on disease/pathogen, no-longer contagious
(c)
The
body returns to normal health
(d)
[convalescence period
(Google Search)]
[index]
(a)
An
inability of the body to fully repair the damage due to an infection can result
in sequelae which are persisting disease aftereffects
(b)
[sequelae and disease
(Google Search)]
[sequelae of acute inflammation]
[the long
term sequelae of missed tendon injuries around the ankle] [the prevention of low birth
weight and its sequelae] [sequelae to pelvic
inflammatory disease] [late sequelae of radiation
therapy to the extremity (must do search to find phrase/heading)] [index]
(64)
Vocabulary [index]
(a)
Acme
(b)
Acute
infection
(c)
Adherence
(d)
Attenuation
(e)
Bacteremia
(g)
Colonization
(h)
Commensalism
(k)
Contamination
(m)
Decline
phase
(n)
Disease
(o)
Endotoxin
(p)
Enterotoxins
(q)
Exotoxins
(r)
Focal
infection
(s)
How microbes cause disease
(x)
Infection
(z)
Intoxication
(aa)
Invasion
(bb)
Invasive
phase
(cc)
Kinds of diseases
(dd)
Koch's
postulates
(ee)
Latent
infection
(ff)
Local
infection
(gg)
Microbe-free regions of the body
(hh)
Microbial antagonism
(jj)
Microbiota
(kk)
Microflora
(ll)
Mixed
infection
(mm)
Mutualism
(nn)
Neurotoxins
(pp)
Normal microflora
(qq)
Normal microbiota
(rr)
Opportunists
(ss)
Parasitism
(tt)
Pathogenicity
(uu)
Period of illness
(vv)
Primary infection
(ww)
Prodromal
period
(xx)
Resident microflora
(yy)
Secondary infection
(zz)
Septicemia
(aaa)
Sequelae
(bbb)
Sign
(ccc)
Stages of an infectious disease
(ddd)
Subacute infection
(eee)
Subclinical infection
(fff)
Superinfection
(ggg)
Symbiosis
(hhh)
Symptom
(iii)
Syndrome
(jjj)
Systemic infection
(kkk)
Toxemia
(lll)
Toxins
(mmm)Toxoid
(nnn)
Transient microflora
(ooo)
Types of diseases
(ppp)
Viremia
(qqq)
Virulence
(rrr)
Virulence factors