of bacteria present. The more bacteria we have, the more waste products we will
also have.
For filamentous organisms, such as molds, a way to measure growth is by dry
weight. The fungus is removed from its growth medium, filtered, and placed in
a weighing bottle dried in a dessicator (a dessicator is a device that removes
water). In bacteria the culture is removed from the medium by centrifugation.Controlling Microbial Growth
It is very important to control microbial growth in surgical and hospital settings,
as well as in industrial and food preparation facilities. There are many terms
used to describe the fight to control microorganisms.
Sterilizationis the destruction of all microorganisms and viruses, as well as
endospores. Sterilization is used in preparing cultured media and canned foods.
It is usually performed by steam under pressure, incineration, or a sterilizing gas
such as ethylene oxide.
Antisepsisis the reduction of pathogenic microorganisms and viruses on liv-
ing tissue. Treatment is by chemical antimicrobials, like iodine and alcohol.
Antisepsis is used to disinfect living tissues without harming them.
Commercial sterilizationis the treatment to kill endospores in commercially
canned products. An example is the bacteria Clostridium botulinum, which
causes botulism.
Asepticmeans to be free of pathogenic contaminants. Examples include proper
hand washing, flame sterilization of equipment, and preparing surgical environ-
ments and instruments.
Any word with the suffix -cide or –cidal indicates the death or destruction of
an organism. For example, a bactercide kills bacteria. Other examples are fungi-
cides, germicides and virucides. Germicides include ethylene oxide, propylene
oxide, and aldehydes. For the same reason, these germicides are also used in pre-
serving specimens in laboratories.
Disinfectionis the destruction or killing of microorganisms and viruses on
nonliving tissue by the use of chemical or physical agents. Examples of these
chemical agents are phenols, alcohols, aldehydes, and surfactants.
Degermingis the removal of microorganisms by mechanical means, such as
cleaning the site of an injection. This area of the skin is degermed by using an
alcohol wipe or a piece of cotton swab soaked with alcohol. Hand washing also
removes microorganisms by chemical means.(^112) CHAPTER 6 Microbial Growth and Controlling It