MICROORGANISMS
Definitions
 Microorganism:
microbe, small
living plant or animal that is not
visible to the naked eye.
 Examples: bacteria, protozoa,
fungi, rickettsiae, and viruses.
Definitions
 Nonpathogens:
microorganisms that
are a part of the normal flora of the
body and are beneficial to
maintaining certain body processes.
 Pathogens: microorganisms that
cause infection and disease . (germs)
From one to another…

Microorganisms that are beneficial in one
area of the body, can become harmful if
they are present in another area of the
body..
 SO..Nonpathogens can become Pathogens!!

Example: E coli is normal in the large
intestine..and aid in digestion..BUT if E
coli is found in the urinary system or blood
it causes infections.
Classifications
 Bacteria:
one celled plants that
multiply rapidly.
 Protozoa: one celled animals found
in decayed materials and
contaminated water.
 Fungi: Simple plantlike organisms
that live on dead organic matter.
Classifications
 Rickettsiae:
parasites..cant live
outside the cells of another
organism.
 Viruses: smallest living organism,
visable only with the use of an
electron microscope.
They cant reproduce unless they are
inside another living cell.
Examples
 Spirilli:
spiral shaped.
– Causes cholera and syphilis.
Examples
 Bacteria:
– Cocci- round or spherical shaped,
occur in pairs chains and clusters.
 Diplococci: pair of cocci
 Streptococci: chains (think of a
strip of cocci)
 Staphlococci: Clusters (think of
grapes)
Examples
Bacteria continued

Bacilli: rod shaped, occurs singly, in pairs,
or in chains. Some contain flagella
(threadlike projections that are similar to
tails that allow bacilli to move)
– Able to form spores (thick walled
capsules) when conditions are poor for
growth.
– Extremely difficult to kill!
Examples
 Protozoa:
amoeba
– Pathogenic ones cause malaria,
amebic dysentery, trichomonas,
and African sleeping sickness.
Examples
 Fungi:
yeast and molds/
 Causes diseases such as
ringworm, athlete’s foot,
histoplasmosis, and thrush.
Examples
 Rickettsiae:
found on fleas,
ticks, and lice, and mites.
 Causes diseases such as typhus
fever, and Rocky Mountain
spotted fever.
Examples

Viruses: HIV and HBV
 Spread from human to human by blood
and body fluids.
 Difficult to kill, resistant to disinfectants,
and are not usually affected by
antibiotics.
 Causes many diseases: AIDS, hepatitis B
colds, measles, mumps, chicken pox,
herpes, warts, flu and polio
What they NEED!
Microorganisms NEED :
Warm environment: body temperature is
ideal
Darkness: again..inside the body is
protected from light..some microbes are
immediately killed by sunlight.
Moisture and Food: blood
Oxygen vs. Nonoxygen

Aerobic: REQUIRE oxygen.
 Anerobic: does NOT REQUIRE oxygen.
– *The human body is an ideal supplier of all the
needs of microorganisms.
Inside or Outside

Exogenous: infections or disease that
originate OUTSIDE the body.

Endogenous: infections or disease that
originate INSIDE the body.
– Example: tumors, congenital abnormalities, or
metabolic disorders.
Nosocomial
 An
infection that originates in the
health care facility.
Example:
Post surgical
Pneumonia
Chain of Infection
Causative Agent
Pathogen
Reservoir
Where Pathogen
lives
Chain of Infection

Portal of Exit:
– Way to escape the
reservoir
– Urine , feces,
saliva, blood, tears,
mucous discharge,
sexual
secretions,and
draining wounds