UNIT 3-Module 10-Ch20_ Antimicrobial Medications.pdf -...

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UNIT 3­Module 10­Ch20: Antimicrobial Medications Ch20: Antimicrobial Medications Describe the discovery of antimicrobial drugs and antibiotics. Chemotherapeutic agents → chemicals that are used to treat disease Antimicrobial drugs→ chemicals used to treat microbial infections Salvarsan → Paul Ehrlich observed some dyes stain bacterial but not animals cells indicating fundamental difference between cell types Prontosil → red dye used to treat streptococcal infections in animals discovered by Gerhard Domagk Antibiotics → chemicals produced by certain molds and bacteria that kills or inhibit the growth of other microorganisms Penicillin→ discovered in 1928 by Alexander Fleming who identified the mold Penicilium which excretes a compound toxic to Staphylococcus. Effective in killing many bacterial species Explain how new generations of antimicrobial drugs are developed. Penicilin G → first naturally produced antimicrobial and antibiotic. Mainly used against Gram­positive bacteria and can also be altered to produce ampicillin. Methicillin → less susceptible to enzymes used by some bacteria to destroy penicillin Today, a variety of penicillin­like medications Describe selective toxicity; antimicrobial action; spectrum of activity; tissue distribution/metabolism/excretion; effects of combinations; adverse effects; and resistance to antimicrobials. Selective toxicity→ causing greater harm to the pathogen than to the host by interfering with essential structures or biochemical processes that are common in microbes but not in human cells Therapeutic index→ a measure of the relative toxicity of a medication. Defined as the ratio of the minimum toxic dose to minimum effective dose. Expressed as lowest dose toxic to patient divided by the dose typically used for therapy If high TI → drug is less toxic If low TI → drug is more toxic If too toxic for systemic use may be used topically Antimicrobial action→ there are different types of antimicrobials Bacteriostatic→ antimicrobial drugs that inhibit bacterial growth. Patient’s defenses are responsible for killing and eliminating pathogen Bactericidal→ antimicrobial drugs that kill bacteria. Are sometimes only inhibitory. 1
UNIT 3­Module 10­Ch20: Antimicrobial Medications Spectrum of activity→ antimicrobial drugs vary in terms of range that they kill microorganisms Broad­spectrum antimicrobials→ inhibit or kill a wide range of microorganisms including both positive and negative Gram bacteria important for treating acute life­threatening diseases very disrupt to the normal microbiota Narrow­spectrum antimicrobials→ inhibit or kill a limited range of bacteria requires identification of pathogen by testing for sensitivity less disruptive to normal microbiota Effects of combinations→ need to be chose carefully as some drugs counteract the effects of others

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