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Chapter 2 : History of Antimicrobial Usage in Agriculture: an Overview
The introduction of antimicrobial drugs into agriculture shortly after the Second World War caused a revolution in the treatment of many diseases of food animals. A broad overview of key features of the history of antimicrobial drug usage in food animals is given, which traces developments from the preantibiotic era to the present day, where there are highly arguable fears that we are moving into the "postantibiotic" era. The majority of antimicrobial drugs used in animals belong to a small number of major classes, and only one new class of antimicrobial drugs, fluoroquinolones has been introduced for food animal use in the last 30 years. Improvements in understanding of the microbiology of infectious diseases acquired from animals were less important, but also critical, forces in the reexamination of antimicrobial usage in agriculture. Ready access to the ‘’miracle drugs’’ by medicine and agriculture, coupled with the ability of chemists to alter existing drugs or develop new ones to counter resistance, led to the expectation that the preantibiotic era was to become a folk memory marked only on mossy gravestones. The new technologies of recombinant DNA, diagnostic DNA microarrays, genomics, proteomics, and combinatorial chemistry hold considerable promise for the development of new, possibly pathogen-targeted, antimicrobial drugs.