BIOL0131_L7 handout_2009

BIOL0131_L7 handout_2009 - Some denitions Basic Medical...

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1 Basic Medical Microbiology Lecture 7 Antibacterial and antiviral agents, and microbial resistance Some defnitions • Antibiotic - antimicrobials oF microbial origin, most are produced by Fungi or the bacterial genus Streptomyces • Antimicrobials, antimicrobic - any substance with suFfcient antimicrobial activity that it can be used to treat inFectious disease • Bactericidal - an antimicrobial that not only inhibits growth but is lethal to bacteria • Bacteriostatic - an antimicrobial that inhibits growth but does not kill the organism • Chemotherapeutic - a broad term that includes antibiotics, antimicrobials and drugs used to treat cancer • Minimal inhibitory concentration (MIC) - a laboratory term that defnes the lowest concentration (in micrograms per litre) to inhibit growth oF an organism • Resistant - organisms that are not inhibited by clinically achievable doses oF an antimicrobial • Sensitive - microorganisms that are inhibited by clinically achievable doses oF an antimicrobial • Susceptible - indicates a microorganism that will be inhibited by clinically achieveable doses • Spectrum - expression oF the categories oF organism against which an antimicrobial is eFFective, narrow spectrum - works on Few bacteria, broad spectrum - works on diverse bacteria
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2 Introduction • Clinically effective antimicrobial agents all exhibit selective toxicity to the pathogen – This is usually because they act on a metabolism or structure that is different to mammalian cells • This is what differentiates them from disinfectants – which are broadly toxic to all microbes 3 sources of antimicrobial agents • Antibiotics – Since they are biological in origin they probably have an important ecological role – The Frst antibiotic, penicillin, was discovered from the fungal genus Penicillium – Cephalosporin antibiotics were discovered from other fungal moulds – The largest source of naturally occurring antibiotics now is a genus of soil-dwelling gram positive branching bacteria called Streptomyces – Antibiotics are mass-produced by fermentation, now a major industry in China - this bacterium produces the antibiotic streptomycin • Chemically synthesized antimicrobial agents – were historically compounds designed for other purposes that were discovered to have antimicrobial activity – Now with greater knowledge of metabolism in pathogens, pathway-speciFc drugs are designed • ModiFed antibiotics – Here chemical modiFcation of existing antibiotics is carried out to improve their action – E.g. penicillinase-resistant penicillin
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3 Antibacterial antimicrobics • Antibacterial agents inhibit either: –Cell wall synthesis –Protein synthesis –Nucleic acid synthesis • Target: cell wall synthesis – Peptidoglycan is the material that gives bacterial cell walls their shape and is unique
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This note was uploaded on 10/28/2010 for the course BIO microbiolo taught by Professor Point during the Spring '09 term at HKU.

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BIOL0131_L7 handout_2009 - Some denitions Basic Medical...

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