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Antibiotics, Features of antimicrobial agents., Historical Origins, Drug…
Antibiotics
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Antimicrobial drugs: A special group of chemotherapeutic agents used to treat disease caused by microbes- by killing pathogenic organism without injuring the host.
Antibiotics are a chemical substance produced by micro-organisms which has the capacity to inhibit growth of ( or even kill) bacteria and other micro-organisms in dilute solution.
From Selman Waksman, 1943. the strict definition mans a " natural product" - nowadays not always the case.
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Antibiotics/ antimicrobial drugs e.g. penicillin) can be safely used systemically to treat infection.
Antiseptic (e.g. benzalkonium chkloride) are not safe ( significant toxicity) for systemic use, but can be safely applied topically.
Disinfectants ( hyper chlorite bleaches) are generally toxic/ harmful/ corrosive and so are used only on inanimate surfaces.
In the UK, the total amount of antibiotics dispensed to humans in 2013 through prescription= 531 tonnes; total for animal use 419 tonnes.
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Historical Origins
Numerous examples of unexplained antimicrobial substances are recorded.
Historically, mostly developed by experience ( empirically) with no knowledge of active ingredients.
Examples
Honey (e.g. Manuka; osmotic effects + ?)
Turmeric (curcumin) anti-bacterial
Hops (phenolic acids, terpenoids)
Cinchona tree (quinine) anti-malarial
Historic origins of synthetic drugs Paul Ehrlich (1910)
First systematic attempt to identify specific antimicrobial chemicals.
Used dyes and developed salvarsan.
(organic arsenic compound) to treat syphilis (Treponema pallidum)
Gerhart Domagk (1932) Identified sulphonamides ( via prodrug Prontosil)
Active against many gram-positive and gram-negative bacteria.
Alexander Fleming British (1881-1955) in (1928) Observed mould Penicillium, which inhibited bacterial cultures.
Howard Florey and Ernest Chain (1940)
Extracted purified and concentrated penicillin for medical use.
Discovered antibiotic production by moulds (penicillin)
Also discovered lysozyme ( enzyme that's lyses bacteria)
Achieved a noble Prize in physiology or medicine 1945: sir Alexander Fleming, Ernst B. Chain, Sir Howard Florey.
the discovery of penicillin depended on " Chance observation" in 1928 he noted " contamination of a culture plate of staphylococci by a mould... for some distance around the mould... lysis was happening. the mould was identified as penicillium sp.
Penicillin was not the first antimicrobial drug.
Drug definition
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Semisynthetic drugs: antimicrobial agents made partly from laboratory synthesis and partly by micro- organisms e.g. amoxicillin.