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In the United States, a vast quantity of antibiotics is routinely included as low doses in
the diet of healthy farm animals, as this practice has been proved to make animals grow
faster. Opponents of this practice, however, point out the likelihood that it also leads to
antibiotic resistance, frequently in bacteria that are known to also infect humans, although
there has been little or no evidence as yet of such transfer of antibiotic resistance actually
occurring.
Antibiotic resistance
One side effect of misusing antibiotics is the development of antibiotic resistance by
the infecting organisms, similar to the development of pesticide resistance in insects.
Evolutionary theory of genetic selection requires that as close as possible to 100% of the
infecting organis ms be killed off to avoid s election of res is tance; if a s mall s ubs et of the
population s urvives the treatment and is allowed to multiply, the average s us ceptibility of
this new population to the compound will be much less than that of the original population,
since they have descended from those few organisms which survived the original treatment.
This survival often results from an inheritable resistance to the compound, which was
infrequent in the original population but is now much more frequent in the des cendants thus
s elected entirely from those originally infrequent res istant organisms .
Antibiotic resistance has become a serious problem in both the developed and
underdeveloped nations. By 1984 half the people with active tuberculos is in the United
States had a strain that resisted at least one antibiotic. In certain settings, such as hospitals
and some child-care locations, the rate of antibiotic resistance is so high that the normal,
low cost antibiotics are virtually useless for treatment of frequently seen infections. This
leads to more frequent use of newer and more expensive compounds, which in turn leads
inexorably to the rise of resistance to those drugs, and a never-ending ever-spiraling race to
discover new and different antibiotics ensues, just to keep us from losing ground in the
battle against infection. The problem of antibiotic resistance is worsened when antibiotics
are used to treat disorders in which they have no efficacy, such as the common cold or other
viral complaints, and when they are used widely as prophylaxis rather than treatment (as in,
for example, animal feeds), because this exposes more bacteria to selection for resistance.
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