adaptive mutations for multiple resistance. Plasmid
transfer accounts for resistance to entire classifica-
tions of drugs such as the quinolones, a family of
antibiotics that attack enzymes that facilitate DNA
cleavage (the division of DNA in preparation for
cell reproduction) in bacteria.
Factors That Contribute to Antibiotic ResistanceAntibiotic use itself is the precipitating factor for
the adaptive changes that occur in bacteria to
result in antibiotic resistance, as these changes
represent natural survival efforts. Key circum-
stances that further encourage survival adapta-
tions include the following:
- Inappropriate prescribing of antibiotics for
infections that are viral or of uncertain cause.
The US Centers for Disease Control and Pre-
vention (CDC) believes about half of the 100
million antibiotic prescriptions US doctors write
each year are unnecessary because the condi-
tions they are treating are not bacterial. - Failing to complete the full course of antibiotic
therapy, which allows some bacteria to escape
eradication. It is important to take a therapeutic
antibiotic long enough to kill all the bacteria,
extending through their complete life cycle,
that are causing infection. Bacteria that are
exposed to the antibiotic but do not die have
the opportunity to undergo adaptive mutation,
which results in antibiotic resistance. - Prophylactic antibiotics given to food animals
such as cattle, pigs, and chickens to prevent
them from getting infections that slow their
growth. The constant exposure to the same
antibiotics fosters adaptive mutation in bacteria
that may then become infective agents in peo-
ple. Humans become vulnerable to infection
from resistant bacteria through eating meat
from treated animals that is not thoroughly
cooked, which allows the bacteria to enter the
body. Exposure to the bacteria in environmen-
tal settings also is a source of infection.
Limiting Antibiotic ResistanceThe most effective measure for reducing antibiotic
resistance is to decrease the use of antibiotics. To
this end, health experts offer these recommenda-
tions for individuals:
- Take antibiotics only for infections that labora-
tory tests prove are bacterial. - Take all doses of the antibiotic for the full
course of prescribed treatment. - Wash hands frequently with soap and warm
water to prevent the spread of infection-caus-
ing bacteria and other pathogens. - Limit exposure to other people who are ill.
- Choose meat and poultry products that are
labeled antibiotic free.
Health experts also are reexamining the prac-
tice of ANTIBIOTIC PROPHYLAXIS(administering antibi-
otics to prevent infection in people who are
IMMUNOCOMPROMISEDor exposed to risk for NOSOCO-
MIAL INFECTIONS). The US Food and Drug Adminis-
tration (FDA), which oversees drug approval and
prescribing practices in the United States, issued
new regulations in 2003 that establish stringent
criteria for doctors to follow in prescribing antibi-
otics and is spearheading public education efforts
to improve public awareness of antibiotic resist-
ance.
See also BACTEREMIA; FOOD SAFETY; HAND WASHING;
OPPORTUNISTIC INFECTION; PATHOGEN; PERSONAL
HYGIENE.antitoxin A serum product, cultivated from ani-
mal (usually horse) BLOOD, that counteracts the
effects of toxins (poisons) certain strains of anaer-
obic BACTERIAproduce when they enter the body.
The antitoxin binds with the toxin that is circulat-
ing in the bloodstream, neutralizing it. Some anti-
toxins, such as those for Clostridium tetani(tetanus)
and Corynebacterium diphtheriae (DIPHTHERIA), are
effective prophylactically (administered to prevent
illness); doctors administer these as vaccines. Oth-
ers are effective therapeutically; doctors adminis-
ter them when exposure triggers illness, such as to
Clostridium botulinum (BOTULISM). Antitoxins for
tetanus and diphtheria also have therapeutic
action in people who develop these conditions.
About 10 percent of people have allergic reactions
to antitoxins. Giving smaller amounts of the anti-
toxin over a longer period of time, such as when
treating disease, often mitigates the reaction.
See also ANTIVENIN; CHILDHOOD DISEASES; PREVEN-
TIVE HEALTH CARE AND IMMUNIZATIONS; VACCINE.antitoxin 151