Stop the prokaryotes (Targets for antibiotic chemotherapy) Flashcards
How can bacterial disease be treated?
By using drugs that are toxic to the bacteria and that causes minimal toxicity to the host
How can treating bactrial disease with drugs that are toxic to the bacteria but not to the host?
Exploit biochemical differences between the infectious organism and the host organism, known as the therapeutic index.
What is the therapeutic index?
It is a comparison of the amount of therapeutic agent that causes the therapeutic effectto the amount that causes toxicity
Can antibiotics be described as bactericidal or bacteriostatic?
yes
What does the bactericidal antibiotic do?
Kills bacteria
What does the bacteriostatic antibiotics do?
Stops bacteria from growing but can also kill bacteria it only takes longer for this to occur
bactericidal antibiotic killing bacteria and bacteriostatic antibiotics stops the bacteria from growing is only relevant in vitro. TRUE OR FALSE?
TRUE
What is the minimum bactericidal concentration (MBC)?
It is the lowest concentration of antibacterial agent that reduces the viability of a bacterial inoculum by greater than equals to 99.9%.
What is Minimum inhibitory concentration (MIC)?
It is the lowest concentration of a chemical which prevents visible growth of a bacterium
When is a drug considered bactericidal?
If the MBC is no more than four times the MIC
How can MIC and susceptibility be determined?
Using standard in vitro test
Briefly describe how an antibiotic susceptibility tests is done?
Strips are impregnated with a gradient of antibiotics are placed on a lawn of bacteria and incubated.
How is MIC determined in an antibiotic susceptibility test?
It is determined at the point where the zero of inhibition intersects the scale.
What are the two strategies for antibacterial chemotherapy and its most common uses?
- Targeting reactions - Used for the vast majority of antibacterial compounds
- Targeting structures - Mostly common in antifungal compounds/ it has limited selection of antibacterial compounds
What occurs in class 1 reactions of anabolic cell metabolism?
- Carbon sources used to produce simple compounds
- The mechanism is similar to eukaryotes and prokaryotes
- Bacteria can utilise alternative carbon sources
What occurs in class2 reactions of anabolic cell metabolism?
- Uses class 1 products used to make small molecules
- Different pathways exist in prokaryotes and eukaryotes
- Same pathway may have differing sensitivity
In the class 2 reaction of the Folate synthesis what counpound is used to inhibit the reaction of p-aminobenzoic acud + pteridine being converted to dihydropteroic acid?
Sulfonamides
In the class 2 reaction of the Folate synthesis what counpound is used to inhibit the reaction of Dihydrofolic acid being converted to tetrahydrofolic acid?
Trimethoprim
What occurs in a class 3 reaction of a anabolic mechanism?
- Small molecules assembled into larger biomolecules
- Every cell must make it’s own biomolecules
- Distinct differences between prokaryotes and eukaryotes pathways
Which one of the class reactions is the best target for antibiotic chemotherapy?
Class 3 reactions
Explain what occurs in tRNA docking?
- Ribosome unit attacheds to mRNA
- tRNA with growing peptide in P site
- tRNA with attached amino acid approaches A site
What drug competes with tRNA for the A site?
Tetracyclines - it prevents the extension of mRNA chain
What occurs in codon:anticodon matching?
Incoming tRNA binds to the A site by complimentary base pairing
What does Aminoglycosides (gentamycin, amikacin etc) do?
It binds to 30S subunit to induce a codon:anticodon mistmatch pairing
What occurs in transpeptidation?
Peptide chain from tRNA on P site moves to tRNA on A site
What does Chloramphenicol macrolides do?
It binds to 50S subunit to inhibit transpeptidation
What does Cycloserine do?
Blocks the addition of AAs
What does Vancomycin do?
Prevents modification
What does Bacitracin do?
Prevents dephosphorylation
What does B-lactams penecillin, cephalosporins etc do?
Prevents polymerisation
What does Erythomycin + spectinomycin + Fusidic acdi do?
Inhibits translocation
What occurs in DNA polymerase?
- DNA double strand formation
- Deoxyribonucleoside triphosphate with complementary base
- DNA polymerase mediated dephosphorylation
- Sugar phosphate backbone attachment
What does Rifampicin amd other related compounds inhibit?
Inhibit polymerisation
What controls the super coiling of E.colis DNA?
DNA gyrase
What does Quinolones inhibit?
Inhibit the supercoiling process
List the 6 different types of target?
- tRNA docking
- Codon:anticodon matching
- Transpeptidation
- Translocation
- DNA polymerisation
- DNA gyrase
