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Compare/contrast Active vs Passive immunity
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Define: Antimicrobial agent
Natural or synthetic chemical that kills or inhibits the growth of microorganisms both in vitro and in vivo (in the living organism).
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Define: Chemotherapeutic agent
Treat microbial disease or prevent proliferation of malignant cells in vivo.
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Nosocomial Infections are what?
Hospital acquired infections, usually antibiotic resistant.
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Define: Sterilization
Treatment that frees the treated object of all living organisms and viruses.
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Define: Death
Irreversible loss of ability to reproduce
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Describe the conditions in which an Autoclave works
15 pounds per square inch above normal atmospheric pressure, water boils at 121C. Holding this temperature for 15 minutes kills endospores.
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Does pasteurization fully sterilize liquids? At what conditions is it performed?
Does not sterilize liquids, but reduces microbial load to safe levels (kills most pathogens, inhibits growth of spoilage microorganisms).
- Originally was 30 minutes at 62C
- Now it's 15 seconds at 72C (flash pasteurization).
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What do the following suffixes mean?
-cidal → _____
-lytic → ______
-static → ______
- -cidal → Kills
- -lytic → Kills by lysis
- -static → Limits growth
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Agar Zone Diffusion involves ________.
Tube Dilution Test involves ________. Bactericidal Tests involves ________.
Agar Zone Diffusion involves zones of inhibition
Tube Dilution Test involves minimum inhibitory concentration
Bactericidal Tests involves transfer to a medium without the agent, and testing for growth.
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Describe the Phenol Coefficient Test. What is it an example of
A comparative test, the greatest dilution that kills the MO at 10 minutes but not 5 minutes is compared to the greatest dilution of phenol that kills the MO at 10 minutes but not 5 minutes.
It is an example of a Bactericidal test
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Describe the Kirby-Bauer Disk Susceptibility Test
A plate test where the diameter of clearing zones of inhibition are measured, and results are compared with a table listing whether a zone size is wide enough to be clinically relevant.
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Does the antimicrobial agent with the largest zone of inhibition in a Kirby-Bauer Disk Susceptibility Test indicate in vivo efficacy?
Not necessarily.
Agents can be effective in vitro but not in vivo
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What is the Minimum Inhibitory Concentration testing for?
Testing for the lowest concentration of the agent that completely inhibits the growth of the test organism.
It is a Bacteriostatic test (tests only for inhibition of growth)
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Who were the significant contributors towards In Vivo – Antimicrobial Agents
Ehrlich, Fleming, Florey, Domagk
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Describe "Salvarsan"
- First antimicrobial agent, discovered by Ehrlich and used in the treatment of syphilis.
- Demonstrated selective toxicity, the ability to inhibit or kill the pathogen without adversely affecting the host.
- Aresnical agent.
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How was penicillin discovered?
Accidentally discovered by Fleming, rediscovered by Florey just before WWII.
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What is the general structure of penicillin? What region can be changed?
The N-Acyl Group is susceptible to change
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What was the change in penicillin that allowed it to broaden to Gm(-) bacteria?
The changing of the N-Acyl group to Ampicillin, which was B-Lactamase resistant
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What is the method of action of Penicillin?
- Inhibit transpeptidase (cross-linking) reaction in bacterial division by binding to transpeptidase (i.e. FtsI in E. coli).
- Cell wall synthesis continues (glycosidic bonds continue to be formed) but eventually lyses regardless.
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What are Cephalosporins?
A molecule similar to penicillin, in that it includes a beta lactam ring, but it contains a six instead of a five membered thiazolidine ring.
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Describe Sulfanilamide
Derived from the dye protonsil, and discovered by Domagk when he was trying to save his daughter from a severe Streptococcal infection.
Protonsil did not produce a zone of inhibition, making it a good example of the fact that not all agents that are effective in vivo are effective in vitro and vice versa.
Inhibits folic acid synthesis in bacteria by acting as a competitive inhibitor to para-aminobenzoic acid. Selectively toxic to bacteria as human beings do not synthesize folic acid.
Some resistance to it has developed.
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What are the Ideal Properties of an Antimicrobial?
- Selective toxicity
- Diffuses to site of infection
- Few side-effects
- Allergic reactions uncommon
- Broad-Spectrum
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What kind of Antivirals are available?
reverse transcriptase inhibitors, etc.
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Are antifungals easy to develop?
No, fungals are difficult to act against since they are Eukarya, but there are some effective agents available
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