ish or even eliminate them. These situations include
the use of chemicals for disinfection, especially in
hospitals, and the protection of our food and water
supplies.
ANTISEPTICS, DISINFECTANTS,
AND STERILIZATION
We are all familiar with the practice of applying iodine,
hydrogen peroxide, or alcohol to minor cuts in the
skin, and we know the purpose of this: to prevent bac-
terial infection. The use of such chemicals does indeed
destroy many harmful bacteria, although it has no
effect on bacterial spores. The chemicals used to pre-
vent infection may be called antiseptics or disinfec-
tants. An antiseptic(anti against; septic infection)
is a chemical that destroys bacteria or inhibits their
growth on a living being. The chemicals named above
are antiseptics on skin surfaces. A disinfectantis a
chemical that is used on inanimate objects. Chemicals
with antibacterial effects may be further classified as
bactericidal or bacteriostatic. Bactericideskill bacteria
by disrupting important metabolic processes.
Bacteriostaticchemicals do not destroy bacteria, but
rather inhibit their reproduction and slow their
growth. Alcohol, for example, is a bactericide that is
both an antiseptic and a disinfectant, depending upon
the particular surface on which it is used.
Some chemicals are not suitable for use on human
skin because they are irritating or damaging, but they
may be used on environmental surfaces as disinfec-
tants. Bleach, such as Clorox, and cresols, such as
Lysol, may be used in bathrooms, on floors or coun-
tertops, and even on dishes and eating utensils (if
rinsed thoroughly). These bactericides will also des-
troy certain viruses, such as those that cause influenza.
A dilute (10%) bleach solution will inactivate HIV, the
virus that causes AIDS.
In hospitals, environmental surfaces are disinfected,
but materials such as surgical instruments, sutures,
and dressings must be sterilized. Sterilizationis a
process that destroys all living organisms. Most med-
ical and laboratory products are sterilized by autoclav-
ing. An autoclaveis a chamber in which steam is
generated under pressure. This pressurized steam
penetrates the contents of the chamber and kills all
microorganisms present, including bacterial spores.
Materials such as disposable plastics that might be
damaged by autoclaving are often sterilized by expo-
sure to ionizing radiation. Foods such as meats may
also be sterilized by this method. Such food products
have a very long shelf life (equivalent to canned food),
and this procedure is used for preparing some military
field rations.PUBLIC HEALTH MEASURES
Each of us is rightfully concerned with our own health
and the health of our families. People who work in the
public health professions, however, consider the
health of all of us, that is, the health of a population.
Two traditional aspects of public health are ensuring
safe food and safe drinking water. Two more recent
aspects are tracking and learning about emerging dis-
eases, and preparing defenses against the possible use
of biological weapons.Food
The safety of our food depends on a number of
factors. Most cities have certain standards and prac-
tices that must be followed by supermarkets and
restaurants, and inspections are conducted on a regu-
lar basis.
Food companies prepare their products by using
specific methods to prevent the growth of microor-
ganisms. Naturally, it is in the best interests of these
companies to do so, for they would soon be out of
business if their products made people ill. Also of
importance is the willingness of companies to recall
products that are only suspected of being contami-
nated. This is all to the benefit of consumers. For
example, since 1925 in the United States, only five
fatal cases of botulism have been traced to commer-
cially canned food. If we consider that billions of cans
of food have been consumed during this time, we can
appreciate the high standards the food industry has
maintained.
Milk and milk products provide ideal environments
for the growth of bacteria because they contain both
protein and sugar (lactose) as food sources. For this
reason, milk must be pasteurized, that is, heated to
145 F (62.9C) for 30 minutes. Newer methods of
pasteurization use higher temperatures for shorter
periods of time, but the result is the same: The
pathogens that may be present in milk are killed,
although not all bacteria are totally destroyed. Milk
products such as cheese and ice cream are also pas-
teurized, or are made from pasteurized milk.
When a food-related outbreak of disease does take
place, public health workers try to trace the outbreak
to its source. This stops the immediate spread of dis-
ease by preventing access to the contaminated food,
and the ensuing publicity on television or in the news-An Introduction to Microbiology and Human Disease 505