Antimicrobial Treatment (Chapter 10) Flashcards
What is the goal of antimicrobial chemotherapy?
To administer a drug to an infected person that destroys the infective agent without harming the hosts cells.
What is an antibiotic?
Microbial products or their derivatives that kill susceptible microbes or inhibit their growth.
Go through the timeline of when the first chemotherapies and antibiotics were developed.
PAUL Ehrlich (1904) - identified trypan dyes that effectively treated African sleeping sickness
Sahachiro HATO (1910) - working with Ehrlich, identified arsenic compounds that effectively treated syphillis
Domagk, Jaques & Therese Trefouel (1935) - discovered sulfonamides and sulfa drugs
Give a timeline of Penicillin
FIRST discovered by ERNEST Duchesne (1896)
NEXT Accidentally discovered by Alexander FLEMING
THEN effectiveness demonstrated by FLOREY, CHAIN, HEATLY (1939) - they got the Nobel prize in 1945 for discovery and production of penicillin
What are the characteristics of antimicrobial drugs and the meanings?
- Selective toxicity
ability of a drug to kill or inhibit pathogen while damaging host as little as possible - Therapeutic dose
drug level required fro clinical treatment - Toxic dose
drug level at which drug becomes too toxic for patient (produces side effects)
What is the Therapeutic Index?
The ratio of a drug that is toxic to humans compared to its minimum effective dose:
the smaller the ratio, the more toxic is it
TI = 1.1 is risky
TI-10 is safer
significane: the drug with the highest TI has the widest margin of safety.
What is a narrow- spectrum drug, a broad-spectrum drug and what’s the difference?
a narrow spectrum drug only attacks a few different pathogens
a broad spectrum drug attacks many different pathogens
What causes the effects of an antimicrobial drug to vary?
concentration, microbe, host
What are the two ways effectiveness is expressed? define them.
- minimal inhibitory concentration (MIC)
lowest concentration of drug that INHIBITS GROWTH of pathogen - minimal lethal concentration (MLC)
lowest concentration of drug that KILLS pathogens
How do disk diffusion tests work?
A disk impregnated with a specific drug are placed on agar plates inoculated with test microbe
the drug DIFFUSES from the disk into the agar, establishing a concentration gradient
clear zones (zones that show inhibition) form around the disks, preventing the growth of that microbe in that region
What are the 3 mechanisms of action for Cell wall synthesis inhibition?
Penicillin
Cephalosporins
Carbapenems
Miscellaneous drugs that target the cell wall
What are the mechanisms of action for cell membrane structure or function?
Polymyxins
What are the 4 mechanisms of action for protein synthesis inhibition?
Amino-gly-co-sides
tetracyclines
Gyl-cyl-cy-clines
Macrolides
Miscellaneous drugs that target the cell wall
What are the mechanisms of action for nucleic acid structure or function inhibition?
fluoro-qui-nolones
What are the mechanisms of action for Folic acid metabolism?
Sulfonamides
What do the folic acid metabolic antagonists do?
block pathways and inhibit metabolism
What do the cell wall inhibitors do?
Block synthesis and repair
What is the significance pf Beta-lactam rings in penicillin and the problems of enzymes that attack it?
bacteria can create penicillinase which is a class of enzymes that cuts the b-lactam ring in penicillin
Why is it difficult to treat organisms growing in biofilm?
They act different than when they are free living.
Antibiotics often cannot penetrate the sticky extracellular material surrounding biofilms
Bacteria in biofilms express a different phenotype and have different antibiotic susceptibility profiles than free living bacteria.
What do you use to treat fungal infections?
Ampho-tercin B
flu-cytosine
What do you use to treat Protozoan disease?
Metro-nidazole
What do you use to treat helminth disease?
Pyrantel
How do you treat viral infections?
Cant use antimicrobiotics but can be prevented with vaccines.
Tamiflu can shorten the course of the flu.
What are the challenges in developing drugs for non-bacterial agents?
disrupting viral metabolism requires disruption of cellular metabolism of host
