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Tortora Microbiology Chap 20 Chemotheraphy


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Any chemical used in treatment, relief, or prevention of disease
Chemotherapeutic agent
Produced by Microorganisms
Produced in laboratory
synthetic drugs
Modification of natural antibiotics
Agent must harm microbes without causing significant damage to host is
selective toxicity
Successfully eliminates organism if the level is maintained over a period of time
Therapeutic dosage level
Causing host damage
Toxic dosage level
The Maximun Tolerable Dose/KG divided by Minimum Dose /KG that cures is
Chemotherapeutic index
A high Chemotherapeutic index indicates
Good selective toxicity
Agents that attack a wide variety of microorganisms
Broad Spectrum agents--can kill both gram + and gram -
Agents that attack a small number of organisms
Narrow Spectrum Agents
Agents that act on an important structure or function in microorganisms which differs from its counter part in animals
Penicillin, bactracin, and cephalosporin are examples of antimicrobials that do what?
Inhibition of cell wall synthesis
Antibiotics that act as detergents and dissolve bacterial cell membranes
Polymyxin antibiotics
How do polymyxin antibiotics work?
Polyene antibodies bind to sterols in fungal membranes
Tetracycline, erythromycin, streptomycin, chloramphenical are examples of
inhibitors of protein synthesis
Inhibition of protein synthesis work on Prokaryotes and Eukaryotes because of?
differences between bacterial and animal ribosomes
Rifamycin is an example of a
inhibitor of nucleic acid synthesis
Two mechanisms of antimetabolites
Competitive inhibition and erroneous incorporation
Erroneous incorporation causes what?
incorrect base pairing
What are the side effects of antibiotics?
Toxicity, Allergy, Disruption of normal flora
Antibiotics do not induce mutations but
select for mutants already present
This mutation often alters DNA that codes for ribosomol proteins
Chromosonal resistance
This mutation is usually due to the presence of plasmids called R factors and are transferred by transformation or conjugation
Extra Chromosomonal resistance
Characteristics of an ideal antimicrobial agent are
Solubility in body fluids, selective toxicity, non allergenic, maintenance of constant therapeutic concentration in blood and tissue fluid, few resistant organisms, long shelf life, and reasonable cost

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