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antibiotic drugsA very extensive range of drugs able to kill or prevent reproduction of bacteria in the body without killing the patient. Antibiotics were originally derived from cultures of living organisms, such as fungi or bacteria, but, today, many are chemically synthesized. The antibiotics have enormously extended the scope and effectiveness of medical therapy against bacterial infection, but have not succeeded in eliminating any bacterial diseases. The extensive, and not always judicious, use of antibiotics has led to widespread evolutionary changes in bacteria in response to their new environment, manifested by the acquisition, by natural selection, of resistance to these drugs. This forces researchers to produce ever new and more effective antibiotics. The antibiotics include such classes as the aminoglycosides, amphenicols, ansamycins, lincosamides, macrolides, polypeptides, tetracyclines and beta-lactams. The beta-lactams include groups such as carbapenems, cephalosporins, cephamycins, monobactams, oxacephems and penicillins.
1. destructive of life.
2. a chemical substance produced by a microorganism that has the capacity, in dilute solutions, to kill (biocidal activity) or inhibit the growth (biostatic activity) of other microorganisms. Antibiotics that are sufficiently nontoxic to the host are used as chemotherapeutic agents in the treatment of infectious diseases. See also antimicrobial.
3. used as feed additives to animals as growth promotants.
a group of antibiotics which have a tetracycline ring structure substituted with the sugar daunosamine. Includes the antineoplastic drugs doxorubicin and daunorubicin.
one that kills bacteria.
one that suppresses the growth of bacteria.
one that is effective against a wide range of bacteria.
on-farm and prepackaged laboratory tests available for testing farm products and animal tissues and fluids for antibiotic residues.
antibiotic feed additives
see feed additives.
first generation antibiotic
one produced as a natural product, e.g. penicillin G. See second generation antibiotic (below).
antibiotic food preservation
is a satisfactory technique but very strictly controlled because of the problem of residues in the food. Used mostly for the preservation of fish.
see pseudomembranous colitis, acute undifferentiated diarrhea of the horse.
antibiotic residue in food
in human food of animal origin is a seriously regarded pollution in public health surveillance. The residues may arise from systemic administration, or even after absorption from a local site such as the uterus, but the most serious contamination arises from milk from quarters that have been treated for mastitis. It is essential for the safety of the human population, the financial well-being of the farmer and the professional reputation of the veterinarian that antibacterial withdrawal times are observed.
see antimicrobial resistance.
second generation antibiotic
produced by manipulation of the molecular structure of a first generation antibiotic (see above) so that the metabolism and pharmacodynamics of the original compound are significantly altered.
antibiotic sensitivity test
see antimicrobial sensitivity test.
antibiotics vary in their absorption from the alimentary tract, requiring some, e.g. streptomycin, to be given parenterally for systemic effect, freedom from toxicity, the range of bacteria against which they are effective, their capacity to stimulate resistance and whether they are bacteriostatic or bactericidal in their effects. Selection of the most suitable antibiotic to suit a particular circumstance may be guided by an antimicrobial sensitivity test, knowledge of the infection present and the price of the drug. In many instances, because of lack of knowledge of the infection present it is necessary to choose an agent with a broad antibacterial spectrum.
antibiotic withdrawal, antibiotic withholding
see antibacterial withdrawal time.