b. Microorganism. A microorganism is an organism that cannot be seen with
the unaided eye. That is, you must use a microscope to see microorganisms. In fact,
some microorganisms (like viruses) are so small that special electronic instruments
called electron microscopes must be used to view them. Bacteria, viruses, protozoa,
and molds are some examples of microorganisms. Microorganisms are sometimes
c. Germ. Germ is a term frequently used by individuals to describe any and all
d. Virology. Virology is the scientific study of viruses.
e. Bacteriology. Bacteriology is the scientific study of bacteria.
f. Mycology. Mycology is the scientific study of fungi.
g. Parasitology. Parasitology is the scientific study of parasites and how these
organisms affect other organisms. Many parasites can be seen with the unaided eye.
h. Disease. A disease is a condition in which there is a malfunction of the body
or an interruption from the body's normal state of health.
i. Pathogen. A pathogen is a disease-producing microorganism.
j. Infection. An infection is a contamination or invasion of any body tissue by a
pathogenic organism. When a microorganism invades the tissue of a human, the
human may be harmed. Many people who have infections have signs and symptoms
that allow physicians to diagnose the condition. The individual with an infection might
experience fever and chills, nausea, vomiting, headache, and/or diarrhea. Needless to
say, a person who has a severe infection wants his prescription to be filled quickly so he
can return to his bed and rest. A patient who has an extremely severe or contagious
infection may be hospitalized and given certain antibiotics intravenously.
k. Toxin. A toxin is a poisonous substance. Some microorganisms produce
toxins that can harm the body. These microbial toxins may be waste products of
metabolism or they may be an integral part of the organism. For example, the bacteria
that cause diphtheria and tetanus (lockjaw) produce their effects by toxins. Some large
plants and animals also produce toxins. There are several types of toxins.