Microbio Final part 2
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Compare/contrast Active vs Passive immunity
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).
Define: Chemotherapeutic agent
Treat microbial disease or prevent proliferation of malignant cells in vivo.
Nosocomial Infections are what?
Hospital acquired infections, usually antibiotic resistant.
Treatment that frees the treated object of all living organisms and viruses.
Irreversible loss of ability to reproduce
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.
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).
What do the following suffixes mean?
-cidal → _____
-lytic → ______
-static → ______
- -cidal → Kills
- -lytic → Kills by lysis
- -static → Limits growth
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.
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
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.
Does the antimicrobial agent with the largest zone of inhibition in a Kirby-Bauer Disk Susceptibility Test indicate in vivo efficacy?
Agents can be effective in vitro but not in vivo
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)
Who were the significant contributors towards In Vivo – Antimicrobial Agents
Ehrlich, Fleming, Florey, Domagk
- 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.
How was penicillin discovered?
Accidentally discovered by Fleming, rediscovered by Florey just before WWII.
What is the general structure of penicillin? What region can be changed?
The N-Acyl Group is susceptible to change
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
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.
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.
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.
What are the Ideal Properties of an Antimicrobial?
- Selective toxicity
- Diffuses to site of infection
- Few side-effects
- Allergic reactions uncommon
What kind of Antivirals are available?
reverse transcriptase inhibitors, etc.
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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