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.