PRINCIPLE OF INFECTIOUS DISEASE AND EPIDEMIOLOGY. Flashcards
are usually free of
microorganisms.
Internal organs
But _____ have extensive
populations of microorganisms.
surface tissues
☐The microbes that normally inhabit a
healthy individual’s body is called
microbiota or “normal flora”.
are specialists, able to
colonize and survive on human tissue.
☐Microbiota
Normal Microbiota of Humans
A. Skin
B. Mouth
C. GI tract
D. Genitourinary tract
Not a great habitat for Normal Microbiota of Humans
Skin
☐dries out, constantly being shed,
skin
Skin dries out, constantly being shed,
secretions include ____&_____
fatty acids
(lower pH to 4-6) and salt
Some skin regions better habitats
than others
☐scalp
☐ears
☐underarms
☐anal region
can
live in sweat glands, hair
follicles, so it is not
eliminated by washing skin.
Propionibacterium acnes
are found on skin and thrive
in nasal region.
Staphylococcus epidermidis
and Staphylococcus aureus,
Saliva contains _____ and other enzymes that kill
bacteria.
lysozymes
adheres to
teeth, especially gum margins, providing microhabitat for other
bacteria to colonize.
Streptococcus mutans and other Streptococcus
Stomach is highly acidic (pH _____)
and kills most microbes.
2-3
Some bacteria and ____ can
tolerate passage through
stomach; few microorganisms
live in stomach.
yeasts
has some
bacteria, but does not proliferate
due to digestive enzymes.
Small intestine
As it approach colon, more and
more bacteria can be seen,
especially
Gram-negative
Enterobacter (e.g. Escherichia coli).
☐Colon has enormous bacterial
population (___ of feces is
bacteria).
1/3
☐Bacteria in colon divide every
____ hours on average, much
slower than laboratory batch
culture rates.
12-24
Upper urinary tract are usually
sterile.
has complex microbiota.
Vagina
After women start periods,
____ is secreted, and _____ bacteria produce lactic
acid, maintain pH ~ 4.5.
glycogen
lactic acid
The good bacteria defend against the bad bacteria by:
☐Competing for attachment sites
☐Competing for nutrients
☐Making antibiotics against invading microbes
☐An infection that results from a prior infection is called a
secondary infection
is when two
organisms live intimately close,
typically over longer periods,
often measured in generations
for at least one of the organisms.
Symbiosis
☐If one organism is
substantially smaller than
the other organism and lives
in or on the larger, then the
larger organism is referred
to as a ____ and the smaller
as a ___.
host
symbiont
is a symbiosis in which both host and symbiont
benefit.
Mutualism
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.
Commensalism
the third category of symbiosis, 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).
Parasitism,
A. Microbial competition
It is the prevention of harmful bacterial growth by a non-
harmful bacterium.
☐Normal microbiota can benefit host by ______ of harmful microorganisms.
preventing
overgrowth
are the more-or-less permanent
members of normal microflora.
Resident microbiota/☐Resident microflora
are present only under unusual
circumstances and only transiently present (hours to
months).
Transient microbiota/☐Transient microflora
are members of the normal microflora that do
not usually cause disease but can be pathogenic under
certain circumstances
Opportunistic microorganisms
Opportunistic microorganisms can be pathogenic under
certain circumstances like:
- Host immunosuppression
- Transfer to other parts of the body
- Elimination of microbial antagonism
study of disease
☐Concerned with etiology as well as structural and
functional changes brought about by the disease.
Pathology
invasion and colonization of body by pathogenic
microorganisms.
Infection
occurs when an infection results in any change
from a state of health.
Disease
☐An abnormal state in which part or all of body is
incapable of performing normal functions.
Disease
an organism’s capacity to cause disease.
Pathogenicity
the degree of disease an organism has the
potential to cause disease.
Virulence
☐Growing the pathogen under conditions that decrease its
adaptation to growth on a given host will decline the
virulence of pathogen
(attenuation).
There are 3 main factors that aid a microbe in becoming
established.
A. It enters or gains access to the body through the
correct (portal of entry.)
B. The (number of cells) that enter the body is enough to
escape the body’s defenses.
C. Other (predisposing factors) that may make the host
more susceptible to disease.
These are the ways to enter the host.
A. Portal of Entry
☐Microbes can’t cause disease unless they enter the body
through the right opening.
A. Portal of Entry
The body has 3 main ways that microbes enter.
- Mucous membranes:
- Skin:
- Parenteral route:
Mucous membranes:
respiratory tract (RT),
gastrointestinal tract (GIT), urogenital tract (UT),
conjunctiva.
unbroken, impenetrable to most people.
SKIN
SKIN ☐Can gain access through
hair follicles, sweat ducts,
abrasions
deposited directly into tissues
beneath skin
Parenteral route:
Parenteral route:
☐Punctures, injections, cuts, wounds, surgery, cracking
Number of cells that enter through the portal of entry
B. Size of Inoculum
One that makes the body more susceptible to a disease and
may alter the course of the disease.
C. Predisposing Factors
C. Predisposing Factors
☐Gender
☐Climate and weather
☐Others include nutrition, age, fatigue, etc.
fimbriae, surface proteins, and capsules are
used by microorganisms to adhere to and colonize body
surfaces.
☐Adhesion:
are
used by microorganisms to adhere to and colonize body
surfaces.
fimbriae, surface proteins, and capsules
Mechanical means such as ________
are used by parasites, such as tape worms, to adhere
and colonize body surfaces.
suckers, hooks, and barbs
Once the organism has made it into the body and attached it
still has to avoid or defend itself from the bodies internal
defenses,_____
immune system.
or other disguises are used by microorganisms
to avoid phagocytosis.
☐Capsules
☐Some microorganisms make chemicals that are toxic to
white blood cells called
leukocidins.
a combination of signs and symptoms that are
characteristic of a disease.
Syndrome
is a characteristic of a disease that can be felt
(by the individual with the disease) but cannot be
measured by another individual.
☐Symptom
is a characteristic of a disease that can be
measured by another individual.
☐Sign
Stages of Disease
A. Incubation period
B. Prodromal period
C. Period of Illness
D. Peak of Illness
E. Period of Decline
F. Period of Convalescence
☐Time interval between the initial infection and the first
appearance of any signs or symptoms.
A. Incubation period
☐The time an infection has begun up to the occurrence of
signs and symptoms.
A. Incubation period
☐Short period that follows the period of incubation in some
diseases when symptoms (and signs) appear, but full-
blown illness has not-yet begun
☐Early, mild symptoms
B. Prodromal period
☐The phase during which the typical signs and symptoms
of the disease are apparent.
C. Period of Illness
☐Most acute stage of the illness
C. Period of Illness
☐Number of white cells increases or decreases
C. Period of Illness
☐The peak of disease symptoms
☐The person exhibits full signs and symptoms of the
disease.
D. Peak of Illness
☐the period during which the signs and symptoms subside
as the infection is brought further under control
☐Patient is susceptible to secondary infections
E. Period of Decline
☐Person regains strength and the body returns to its pre-
diseased state
F. Period of Convalescence
are persisting disease after infection
☐The inability of the body to fully repair the damage
due to an infection
☐Sequelae
The period during which the disease is spread is dependent
upon the infecting organism.
F. Period of Convalescence
For example, some organisms are contagious before signs
and symptoms are manifest.
Others are contagious during the worst portion of the manifest
signs and symptoms.
F. Period of Convalescence
properties of a pathogens that allow them
to cause disease. Any characteristic or structure of the
microbe that helps it to establish itself in the host or cause
damage in the host.
Virulence factors
are used in adhesion to hosts
☐Pili
used to evade host defenses or to harm the
host directly
☐Enzymes
are substances produced, for example, by
microorganisms, that are poisonous to host organisms
☐Toxins
Bacterial toxins may be classified as either
exotoxins or
endotoxins.
are produced predominantly (though not
exclusively) by Gram-positive bacteria
Exotoxins
☐Made inside a living microbe and release into the
surrounding environment.
☐Can be converted to toxoid*
Exotoxins
Some exotoxins are
exoenzymes
that catalyze the lysis of red blood cells
☐Hemolysins
exoenzymes:
☐Mucinase, keratinase, collagenase, hyaluronidase
kills host cells by damaging the cell memb.
☐Cytotoxins
act on nervous system tissue
☐Neurotoxins
act on tissues of the gastrointestinal tract
☐Enterotoxins
Are toxins associated with Gram-negative bacteria
Endotoxin
☐The lipid A portion of the lipopolysaccharide
☐Weak except in large doses and produce similar effects
independent on the producing organism
☐Large doses are especially a problem during Gram-
negative septicemia
Endotoxin
is a disease that involves pathogen.
Infectious disease
is an infectious disease that
may be passed from host to host (particularly when all
individuals involved are of the same species)
Communicable disease
is easily passed from individual to
individual.
Contagious disease
B. Types of Infection
acute
chronic
subacute
latent
inapparent
local
focal
systemic
primary
secondary
superinfection
mixed
Nosocomial
infection develops rapidly but is soon over
acute
infection develops slowly and is not soon
over
chronic
infection is the gray zone between acute
and chronic
subacute
infection is sign-less or symptom-less for a
long while before signs and symptoms appear
latent
infection that does not display signs or
symptoms or, at least, all of the signs typically
associated with a given syndrome.
inapparent infection
infection is confined to a certain area (e.g., a
pimple).
local infection
infection begins as a local infection but then
spreads beyond the local area as a bacteremia, or
toxemia.
focal infection
infection is spread throughout the body in
the blood or lymph.
systemic infection
infection is the infection of a not-currently
infected person.
primary infection
infection is an infection that quickly
follows a primary infection
secondary infection
is a secondary infection caused by
the treatment of a primary infection
superinfection
infection is a syndrome that is caused by a
combination of two or more infections
mixed infection
infections are acquired from the hospital
Nosocomial infections
C. Blood Invasion
Septicemia
Bacteremia
Fungemia
Toxemia
Viremia
is the growth of bacteria in the blood
(a.k.a., blood poisoning)
Septicemia
is the presence, without multiplication, of
bacteria in the blood.
Bacteremia
is the presence of fungus in the blood
Fungemia
is the presence of toxins in the blood
Toxemia
is the presence of virus in the blood
Viremia
The means, or logic, by which a specific microorganism is
classified as the cause of a disease.
Koch’s Postulates
