Introduction:
They are in the air
we breathe . . .
In our food .
. .On our skin .
. .
-on everything
we touch.
They are .
. .
microorganisms
What are
microorganisms?
(also called microbes)
Microbes are small living plants or
animals most of which are not visible to
the naked eye.
Some microbes cause disease or infection.
Many microbes are “good” organisms that
help keep balance in the environment
and the body.
What microbes lack in size,
they make up in number.
On the average human, there are
about 100 trillion microbes.
Good vs. Bad
Microorganisms:
Microorganisms that cause disease
(germs) are referred to as pathogens.
Yeah,
I’m bad.
Microorganisms that are
harmless or beneficial are
called nonpathogens.
Most microbes are considered
beneficial or harmless.
87%
beneficial organisms
10%
Pathogens 3%
opportunists
The role of good
microorganisms
Marine & freshwater microbes form
the basis of the food chain in oceans,
lakes, and rivers.
Soil microbes help
break down wastes.
Humans and other
animals depend on
bacteria in their
intestines for digestion
and synthesis of
vitamins including:
vitamin B (for metabolism)
vitamin K (for blood clotting)
Microorganisms have many
commercial applications
They are used in synthesis of chemical
products such as:
acetone
organic
acids
alcohol
enzymes
many
drugs
They are used in the
food industry for producing:
pickles
vinegar
cheese
alcoholic beverages
green olives
bread
yogurt
 Aerobic organisms:
 Anaerobic organisms:
 Most microorganisms prefer
warm, dark environments
Main Classes of Pathogenic
Organisms:
1) Bacteria
• simple one-celled organisms
• At home within “climate” of human body
• compose largest group of pathogens
2)Fungi: yeasts & molds
• Plant-like organisms that live on dead
organic matter
• Grow best in dark, damp places
3) Viruses - smallest microbes
•acellular particles (not a complete cell)
4) Protozoa
•one-celled animals often found in decayed
materials & contaminated water
5) Helminths
•parasitic worms
•caused by larval & egg infestations
Bacterial Infections
Impetigo
highly contagious bacterial infection
Extensive case of impetigo
on underarm of baby.
Fetal Tetanus
(note severe muscle contractions)
Due to toxin production as a result of bacterial
infection.
Diphtheria
Note swelling in neck
Diphtheria membrane
Cellulitis
An acute bacterial
inflammation of
connective tissue.
Lyme's Disease
hallmark “bulls-eye” lesion
Tiny deer tick vector that transmits
lymes disease.
Fungal Infections
Candidiasis: Oral Thrush
Oral Thrush:
tongue
Candidiasis of Skin
Typical red, slightly most lesions.
Nail Fungus
Black Hairy Tongue
Cutaneous Fungal Infection:
Tinea Versicolor
Note: hypopigmented fungal lesions
Cutaneous Fungal Infection:
Ringworm
Cutaneous Blastomycosis: Hand & Wrist
Subcutaneous
Blastomycosis:
Manifested by
subcutaneous
abscesses in upper
chest
Chromomycosis
Deep fungal infection
with granulomatous
lesions.
Viruses
Viral Infection: Verruca Vulgaris (Wart)
Herpes Type I: Oral Herpes
More Oral Herpes
healing stage
Neonatal Herpes
Premature infant born with classic
“cigarette burn” pattern of HSV infection.
Poliomyelitis
(also called infantile
paralysis)
Note: deformed
right leg
Iron Lung: used by polio victims
Varicella (Chickenpox with oral
involvement)
Measles
(rubeola)
Rash usually begins
on face and spreads
to trunk and
extremities.
Mumps:
Note edema to cheeks and neck
Viral Hepatitis
Severely distended
abdomen (ascites).
Secondary complication
from hepatitis.
Parasitic & Protozoan
Infections
Leishmaniasis
(protozoan systemic
disease)
Severe nodular,
disfiguring lesions
transmitted by sand fly
Dracunculiasis (Fiery Dragon Worm)
Found just under skin of human host.
Causes blisters at site of infestation.
Ulceration from worm.
A fiery dragon worm emerges
from leg.
Elphantiasis
(filariasis)
Elphantiasis
affecting left leg and genitals
Intestinal helminthes
cause infestations in
intestinal tract and
abdominal organs such
as the liver and spleen.
Always in pairs.
Helminthes which
have infested the
liver.
hepatomegaly and
ascites
Intestinal Roundworms
Mass of 800 worms removed from child’s
ileum during autopsy
Loa Loa eye worm infestation in
conjunctiva
Loa loa being extracted from under
conjunctivia.
Hydatid cyst formed by tiny tapeworm that
migrated to brain.
That’s all folks.
1. Hepatitis B
2. Hepatitis C
3. AIDS

virus that is
spread through
blood, serum
and other body
secretions. It
affects the
liver.

virus that is spread through blood. It affects
the liver and can lead to destruction of the
liver and eventually death. There is a 3
series vaccination that can help protect for
getting the virus.

a virus that suppresses the immune system.
People with AIDS cannot fight off infection
that would not affect a healthy person. It is
transmitted through blood and body
secretions.

It is very important as a
health care worker to take
every precaution against
contracted these viruses.
Good hand washing,
always wear gloves and
other protective
equipment, and use
caution when drawing
blood or giving injections,
are just a few safety
precautions
Summary
•Microbes are microscopic organisms
•About 100 trillion microbes live on the
average human
•“Bad” microbes are pathogens
•About 3% of microorganisms are
pathogenic
•Main classes of pathogenic microbes
include: bacteria, fungi, viruses,
protoza, & helminths



Causative agent: pathogen such as a
bacteria or virus
Reservoir: place for the causative agent
(virus) to live. Such as the human body
Fomites: objects that are contaminated
with infectious material that contains
pathogens (Examples: door knobs, bed
pans, linens and specimen containers)

means the infection or the disease originates
within the body (Examples: tumors,
metabolic disorders, and congenital
abnormalities

means the infection or disease originated
from outside the body (Examples: radiation,
chemical agents, trauma, and temperature
extremes

Infection that is acquired
by an individual in a health
care facility such as a
hospital or nursing facility.
These infections are
usually passed to the
patient by the health care
worker (Examples: staph
infection, and
pseudomonas)

Type of infection that occurs
when the body’s defenses
are weak. These diseases
usually do not occur in
healthy people (Examples:
kaposi’s sarcoma, rare type
of cancer or different types
of pneumonia in people who
have AIDS


Antisepsis: Prevent or inhibit growth of
pathogenic organisms but are not effective
against spores and viruses.
Examples: Alcohol and betadine
Disinfection: process that destroys or kills
pathogenic organisms. Not always effective
against spores and viruses.
Example: Chemical disinfectants



Sterilization: process that destroys all
microorganisms, both pathogenic and
nonpathogenic, including spores and viruses.
Autoclave: is the most common piece of
equipment used for sterilization