34_lecture - Chapter 34 Antimicrobial Chemotherapy 1...

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Unformatted text preview: Chapter 34 Antimicrobial Chemotherapy 1 chemical agents used to treat disease destroy pathogenic microbes or inhibit their growth within host most are antibiotics microbial products or their derivatives that kill susceptible microbes or inhibit their growth 2 Chemotherapeutic Agents 3 Figure 34.1 selective toxicity ability of drug to kill or inhibit pathogen while damaging host as little as possible therapeutic dose drug level required for clinical treatment toxic dose drug level at which drug becomes too toxic for patient (i.e., produces side effects) therapeutic index ratio of toxic dose to therapeutic dose 4 General Characterisitics of Antimicrobial Drugs side effects undesirable effects of drugs on host cells narrow-spectrum drugs attack only a few different pathogens broad-spectrum drugs attack many different pathogens cidal agent - kills microbes static agent - inhibits growth of microbes 5 General Characteristics of Antimicrobial Drugs effect of an agent may vary with concentration, microbe, host effectiveness expressed in two ways minimal inhibitory concentration (MIC) lowest concentration of drug that inhibits growth of pathogen minimal lethal concentration (MLC) lowest concentration of drug that kills pathogen 6 General Characteristics of Antimicrobial Drugs dilution susceptibility tests for MIC disk diffusion tests Kirby Bauer the E-test MIC and diffusion 7 Determining the Level of Antimicrobial Activity involves inoculating media containing different concentrations of drug broth or agar with lowest concentration showing no growth is MIC if broth used, tubes showing no growth can be subcultured into drug-free medium broth from which microbe cant be recovered is MLC 8 Dilution Susceptibility Tests disks impregnated with specific drugs are placed on agar plates inoculated with test microbe drug diffuses from disk into agar, establishing concentration gradient observe clear zones (no growth) around disks 9 Disk Diffusion Tests 10 Table 34.2 standardized method for carrying out disk diffusion test sensitivity and resistance determined using tables that relate zone diameter to degree of microbial resistance table values plotted and used to determine if concentration of drug reached in body will be effective 11 Kirby-Bauer Method 12 Figure 34.2 13 Figure 34.3 convenient for use with anaerobic pathogens similar to disk diffusion method, but uses strip rather than disk E-test strips contain a gradient of an antibiotic intersection of elliptical zone of inhibition with strip indicates MIC 14 The E Test 15 Figure 34.4...
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This note was uploaded on 02/04/2012 for the course BIO 326R taught by Professor Whiteley during the Spring '08 term at University of Texas at Austin.

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34_lecture - Chapter 34 Antimicrobial Chemotherapy 1...

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