Stop the prokaryotes (Targets for antibiotic chemotherapy)

Question 1

How can bacterial disease be treated?

Answer 1

By using drugs that are toxic to the bacteria and that causes minimal toxicity to the host

Question 2

How can treating bactrial disease with drugs that are toxic to the bacteria but not to the host?

Answer 2

Exploit biochemical differences between the infectious organism and the host organism, known as the therapeutic index.

Question 3

What is the therapeutic index?

Answer 3

It is a comparison of the amount of therapeutic agent that causes the therapeutic effectto the amount that causes toxicity

Question 4

Can antibiotics be described as bactericidal or bacteriostatic?

Answer 4

yes

Question 5

What does the bactericidal antibiotic do?

Answer 5

Kills bacteria

Question 6

What does the bacteriostatic antibiotics do?

Answer 6

Stops bacteria from growing but can also kill bacteria it only takes longer for this to occur

Question 7

bactericidal antibiotic killing bacteria and bacteriostatic antibiotics stops the bacteria from growing is only relevant in vitro. TRUE OR FALSE?

Answer 7

TRUE

Question 8

What is the minimum bactericidal concentration (MBC)?

Answer 8

It is the lowest concentration of antibacterial agent that reduces the viability of a bacterial inoculum by greater than equals to 99.9%.

Question 9

What is Minimum inhibitory concentration (MIC)?

Answer 9

It is the lowest concentration of a chemical which prevents visible growth of a bacterium

Question 10

When is a drug considered bactericidal?

Answer 10

If the MBC is no more than four times the MIC

Question 11

How can MIC and susceptibility be determined?

Answer 11

Using standard in vitro test

Question 12

Briefly describe how an antibiotic susceptibility tests is done?

Answer 12

Strips are impregnated with a gradient of antibiotics are placed on a lawn of bacteria and incubated.

Question 13

How is MIC determined in an antibiotic susceptibility test?

Answer 13

It is determined at the point where the zero of inhibition intersects the scale.

Question 14

What are the two strategies for antibacterial chemotherapy and its most common uses?

Answer 14

1. Targeting reactions - Used for the vast majority of antibacterial compounds
2. Targeting structures - Mostly common in antifungal compounds/ it has limited selection of antibacterial compounds

Question 15

What occurs in class 1 reactions of anabolic cell metabolism?

Answer 15

• Carbon sources used to produce simple compounds
• The mechanism is similar to eukaryotes and prokaryotes
• Bacteria can utilise alternative carbon sources

Question 16

What occurs in class2 reactions of anabolic cell metabolism?

Answer 16

• Uses class 1 products used to make small molecules
• Different pathways exist in prokaryotes and eukaryotes
• Same pathway may have differing sensitivity

Question 17

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?

Answer 17

Sulfonamides

Question 18

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?

Answer 18

Trimethoprim

Question 19

What occurs in a class 3 reaction of a anabolic mechanism?

Answer 19

• Small molecules assembled into larger biomolecules
• Every cell must make it’s own biomolecules
• Distinct differences between prokaryotes and eukaryotes pathways

Question 20

Which one of the class reactions is the best target for antibiotic chemotherapy?

Answer 20

Class 3 reactions

Question 21

Explain what occurs in tRNA docking?

Answer 21

1. Ribosome unit attacheds to mRNA
2. tRNA with growing peptide in P site
3. tRNA with attached amino acid approaches A site

Question 22

What drug competes with tRNA for the A site?

Answer 22

Tetracyclines - it prevents the extension of mRNA chain

Question 23

What occurs in codon:anticodon matching?

Answer 23

Incoming tRNA binds to the A site by complimentary base pairing

Question 24

What does Aminoglycosides (gentamycin, amikacin etc) do?

Answer 24

It binds to 30S subunit to induce a codon:anticodon mistmatch pairing

Question 25

What occurs in transpeptidation?

Answer 25

Peptide chain from tRNA on P site moves to tRNA on A site

Question 26

What does Chloramphenicol macrolides do?

Answer 26

It binds to 50S subunit to inhibit transpeptidation

Question 27

What does Cycloserine do?

Answer 27

Blocks the addition of AAs

Question 28

What does Vancomycin do?

Answer 28

Prevents modification

Question 29

What does Bacitracin do?

Answer 29

Prevents dephosphorylation

Question 30

What does B-lactams penecillin, cephalosporins etc do?

Answer 30

Prevents polymerisation

Question 31

What does Erythomycin + spectinomycin + Fusidic acdi do?

Answer 31

Inhibits translocation

Question 32

What occurs in DNA polymerase?

Answer 32

• DNA double strand formation
• Deoxyribonucleoside triphosphate with complementary base
• DNA polymerase mediated dephosphorylation
• Sugar phosphate backbone attachment

Question 33

What does Rifampicin amd other related compounds inhibit?

Answer 33

Inhibit polymerisation

Question 34

What controls the super coiling of E.colis DNA?

Answer 34

DNA gyrase

Question 35

What does Quinolones inhibit?

Answer 35

Inhibit the supercoiling process

Question 36

List the 6 different types of target?

Answer 36

1. tRNA docking
2. Codon:anticodon matching
3. Transpeptidation
4. Translocation
5. DNA polymerisation
6. DNA gyrase