Antibiotics and antimicrobial resistence

Question 1

Who is Paul Ehrlich?

Answer 1

-Came up with precursor to gram stain
-First treatment for syphilis - Treponema pallidum - first example of chemo

Question 2

What is a growth factor analogue?

Answer 2

A substance related to a growth factor but blocks the utilisation of the growth factor e.g the sulfa drugs

Question 3

Who is Sir Alexander Fleming?

Answer 3

-Prof of bacteriology at st Marys Hospitak in London
-1922 discovered lysozyme
-While growing staphylococcus aureus, found penicillium notam (penecillin) would prevent may bacterial growth

Question 4

Who then worked on purification of penicillin after Fleming?

Answer 4

Howard Florey and Ernest Chain
-found penicillium chrysogenum would give much more penicillin

Question 5

Who isolated streptomycin from streptomyces griseus and proposed the term antibiotic?

Answer 5

Selman Waksman

Question 6

How can prokaryotes become resistant to antibiotics?

Answer 6

-natural resistance
-acquisition of resistance genes
-mutation of antibiotic target

Question 7

Look at targets of antibiotics diagram

Question 8

Example of narrow spectrum antibiotic?

Answer 8

Penicillin - gram neg usually resistant

Question 9

Example of broad spectrum antibiotic?

Answer 9

Tetracycline - effective against gram neg and pos bacteria

Question 10

Bacteriocidal vs bacteriostatic vs bacteriolytic

Answer 10

Bacteriocidal - kill bacteria
Bacteriostatic - stop them from ngrowing
Bacteriolytic - lyse the cells entirely

Question 11

What do the majority of antibacterial drugs target?

Answer 11

The cell wall

Question 12

What are ß-lactam antibiotics and what do they do and examples?

Answer 12

-Inhibit cell wall synthesis
-Targets transpeptidation - rxn that crosslinks 2 glycan linked peptide chains in peptidoglycan
-2/3 of antibiotics produced
-Penicillins, cephalosporins
-Have a ß-lactam ring

Question 13

Are Gram pos or gram neg for susceptible to ß-lactam antibiotics?

Answer 13

Gram Positive cells
-Newly formed peptidoglycan layer has 2 D-Ala- one of which is cleaved to allow lining (transpeptidation)

Question 14

What does Penicillin G act against?

Answer 14

Gram pos bacteria

Question 15

Example of semi-synthetic penicillins? How are they formed?

Answer 15

-Ampicillin
-Carbenicillin
By a n-acetyl group modification

Question 16

Bacterial resistence to penicillin enzyme?
What has to be used to prevent this?

Answer 16

Penicillinase (ß Lactamase)

ß lactamase inhibitors must be used e.g augmentin or clavamox which is clavulanic acid and amoxycillin

Question 17

Semisynthetic penicillin - Methicillin?
Oxacillin?

Answer 17

Both - acid-stable, ß-lactamase-resistant

Question 18

Semisynthetic penicillins - Ampicillin and Carbenicillin?

Answer 18

Both - broadened spectrum of activity, acid-stable, ß-lactamase-sensitive
Ampicillin - esp effective against gram neg bacteria
Carbenicillin - esp effective against Pseudomonas aeruginosa, ineffective orally

Question 19

What are cephalosporins, what do they do?

Answer 19

-Fungus species Cephalosporium
-Beta-lactam ring
-Func same as penicillins - bond irreversibly to transpeptidases and prevent cross-linking of peptidoglycan
-Semi- synthetic
-Broader spectrum that penicillins
-Usually more resistant to beta- lactamases

Question 20

What kind of antibiotic is vancomycin and what does it inhibit?

Answer 20

Glycopeptide antibiotic
Inhibits cell wall synthesis

Question 21

How do bacteria respond to antibiotics that inhibit cell wall synthesis?

Answer 21

Have a thicker cell wall

Question 22

What eaxctly do ß-lactams do to inhibit cell wall synthesis?

Answer 22

Inhibit transpeptidase directly

Question 23

What exactly does vancomycin do to inhibit cell wall synthesis?

Answer 23

Inhibits transpeptidation reaction

Question 24

What does cycloserine do exactly to inhibit cell wall synthesis?

Answer 24

Inhibits synthesis of building blocks

Question 25

What does bacitracin do exactly to inhibit cell wall synthesis?

Answer 25

Inhibits the transport of building blocks

Question 26

Example of cell membrane inhibitor?

Answer 26

Polymyxins - produced by some Bacillus spp
-Bind tightly to lipid A component of LPS (outer membrane of g neg)

Question 27

How is daptomycin affective?

Answer 27

-Active in gram-pos bacteria
-Disruption of bacterial membrane through formation of transmembrane channels

Question 28

Examples of antibiotics that are inhibitors of protein synthesis?

Answer 28

-Chloramphenicol
-Aminoglycosides : streptomycin, neomycin, gentamycin
-Tetracyclines (Rickettsias and chlamydia)
-Macrolides: Erythromycin (gram pos, used in children)

Question 29

Macrolides - what does clarithromycin do?

Answer 29

-Binds to 50S ribosome
-Proetin synthesis inhibitor
-Respoiratory infections

Question 30

Example of inhibitor of nucleic acid synthesis 1?

Answer 30

Rifamycin / rifampin
-inhibits RNA synthesis
-antituberculosis
-source: streptomyces mediterranei

Question 31

Example of inhibitor of nucleic acid synthesis 2?

Answer 31

Quinolones and fluoroquinolones
-Ciproflaxacin
-Inhibits DNA gyrase
-UTIs