23_lecture_Antibiotics

23_lecture_Antibiotics - A n tib io tic s a n d R e s is ta...

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Antibiotics and Resistance Antibiotics and Resistance 1. Antibiotics and clinical microbiology 2. Types of antibiotics 3. Mechanisms of action 4. Test for antibiotic sensitivity 5. Antibiotic resistance 6. Solutions Figure References : • Walsh, C. . 2000. Molecular mechanisms that confer antibacterial drug resistance. Nature 406:775 • Levy, S. and Marshall, B. . 2004. Antibacterial resistance worldwide: causes, challenges and responses. Nature Medicine 10(12):S122-S129 TOPICS Hospital and Clinical Microbiology • Implement an infection control program • Perform hospital surveillance. – Nosocomial infections – Fomites • Report epidemiological findings to physicians • Perform microbial epidemiology – Typing strains – Monitoring strain diversity – Culture collection Chemotherapeutic agents • 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 • Distinct from antimicrobial agents – Not intended for therapeutic purposes – Naturally occurring and/or synthetic – Used to sterilize or inhibit microbial growth Before “modern” antibiotics metals solutions were used. • Arsenic – Used since antiquity – was one of the first antimicrobial compounds and was effective against syphilis. – Arsenic is very toxic to the patient however. • Mercury – Very effective antimicrobial agent. – Used to sterilize surfaces and kill microbes – Still used as preservative in vaccines • Bacteria can develop really high levels of resistance to metals (5-10 mM!).
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General effects of Ab on bacteria Disruption of cell wall and/or membranes Interferes with protein/DNA synthesis The Development of Chemotherapy • Paul Ehrlich (1904) – Developed concept of selective toxicity – Identified dyes that effectively treated African sleeping sickness – One of the first is salvarsan (arsenic containing drug) • Alexander Fleming accidentally discovered penicillin (1928) – Observed penicillin activity on contaminated plate • Selman Waksman discovered streptomycin (1944) The original The original Penicillum Penicillum plate plate Alexander Fleming Alexander Fleming drawings and notes drawings and notes General Characteristics of Antimicrobial Drugs • 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
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Mechanism of Action of Antimicrobial Agents • Can impact pathogen by targeting some function necessary for its reproduction or survival • Targeted function is very specific to
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This note was uploaded on 12/03/2011 for the course BIO 118 taught by Professor Staff during the Fall '08 term at Rutgers.

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23_lecture_Antibiotics - A n tib io tic s a n d R e s is ta...

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