 MIDDLE
SCHOOL KIT:
Activity 3
Viruses vs. Bacteria. Viruses
are very different from bacteria. For one thing, they are much smaller. Viruses
cannot be seen through an ordinary microscope. For another, we are not sure
they are really alive. They act like robots that can turn on and turn off.
For more on the differences between viruses and bacteria, go to Bugs! on
the Save the Antibiotic Website.
Here
are images of six viruses that cause disease in
humans:
- Adenovirus (click
here for the image). The Human Adenoviruses
most commonly cause respiratory illnesses like
colks, pneumonia, croup and bronchitis. Some adenoviruses
can cause infections of the bowel or bladder.
- Coxsackie
B virus (click
here for the image). Coxsackie B virus diseases
can range from relatively minor gastrointestinal upsets
to paralysis, cardiac damage, and birth defects,.
- Hepatitis
A virus (click
here for the image). Hepatitis A is a viral infection
of the liver caused by hepatitis A virus. The illness
may be mild, lasting a week or two, or severely disabling.
- Norwalk virus
(click
here for the image). The Norwalk virus is a leading
cause of foodborne disease in the United States. The
symptoms include nausea, diarrhea, vomiting and stomach
cramps.
- Poliovirus (click
here for image). Polio is an infectious disease
caused by a the Human Poliovirus. It can strike
at any age, but affects mainly children under three
(over 50% of all cases). The disease causes paralysis,
which is almost always permanent. Fortunately,
this dread disease has almost been wiped out all
across the globe. Check out the Polio
Eradication Website.
- Rhinovirus (click
here for image). Billions of people catch colds
every year. Two thirds of them are caused by the
Rhinovirus.
The following five images are of bacteria
that cause human illnessses:
- Campylobacter jejuni (click
here for the image). Most people who become
ill with campylobacteriosis get diarrhea, cramping,
abdominal pain, and fever.
- Cholera (click
here for the image). A person may get cholera
by drinking water or eating food contaminated with
the cholera bacterium. In an epidemic, the source
of the contamination is usually the feces of an
infected person.
- Salmonella (click
here for the image). Salmonellosis is a common
form of food poisoning. Most persons infected with
Salmonella develop diarrhea, fever, and abdominal
cramps.
- Shigella (click
here for the image). Most who are infected
with Shigella develop diarrhea, fever, and stomach
cramps starting a day or two after they are exposed
to the bacterium. Most Shigella infections are
the result of the bacterium passing from stools
or soiled fingers of one person to the mouth of
another person.
- Streptococcus
pyogenes (click
here for the image). Streptococcus pyogenes
is one of the most frequent pathogens found in
humans. These bacteria are the causes of pharyngitis
(Strep Throat), scarlet fever, impetigo and the
rare but severe invasive infections described in
the news media as "flesh-eating
bacteria." There's more information on the University
of Wisconsin – Madison Website.
Mechanism of infection: Bacteria.
When
bacteria infect the body they reproduce quickly,
forming colonies that feed on nutrients in the
host cells. The mechanism of infection may be different
for different kinds of bacteria. Enteropathogenic
E. coli attach to the wall of an intestinal cell
and build a platform from which to begin reproduction.
Mechanism
of infection: Viruses.
Viruses
cannot reproduce by themselves. Instead, they infect
cells by injecting DNA through the cell wall. The
viral DNA takes control of the cell and turns it
into a factory for producing more viruses.
How
antibiotics affect viruses.
Penicillin kills bacteria by interfering with
the bacterial cell's ability to build new cell wall.
When the cell expands, getting ready to divide, the cell
wall stretches and breaks.
Click
here
to enlarge image
Note
that growth of the bacteria Staphylococcus
aureus is inhibited in the area surrounding
the invading penicillin-secreting Penicillium
mold colony.
Slide by Christine L. Case, Ed.D
Professor
of Microbiology
Skyline College, California |
Reducing
the spread of infectious diseases
Washing your hands regularly may be the single
best way to stay well yourself, and prevent the spread
of infectious diseases. There are more simple things
you can do at home and at school to fight infection.
To learn about them, visit the Bugbusters section of
the Save the Antibiotic Website.
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