ISB 1 Intro

Question 0

Penicillin G is used to treat

Admin via

Answer 0

For STIs such syphilis
Via injection

Was the first antibiotic made

Question 1

Why can concentration of antibacterials be high?

Answer 1

Don’t generally have mammalian targets

Question 2

Why is pen G not delivered orally

Answer 2

V reactive square right cleaved by acids and bases

Question 3

Oral alternative to pen g?

Answer 3

Pen v

- more stable we don’t know why, still not 100% BA though

Question 4

If it’s resistant to this it’s resistant to everything…

Why?

Answer 4

Methicillin

It’s bulky and doesn’t fit into the active site that cleaves the ring

Question 5

Contrast four generations of ceplasporins

Answer 5

2 more selective
3 injection only, fantastic gram neg killers
4 attempt to get oral BA but not as good

Question 6

Having a bacterial cell wall makes things more or less resistant?

Answer 6

More - traps beta lactamases

Question 7

Beta lactams have a ……. membered lactam ring

Answer 7

Four

Question 8

Beta lactams fit beautifully where..

Answer 8

Into enzymes building the cell wall

It’s about distance and angle

Question 9

Why are humans not affected by beta lactams

Answer 9

They cannot produce D Ala anyway. And these mimic D

Ala

Question 10

Penicillin binding proteins are actually

Answer 10

Enzymes - what a silly name

Question 11

What happens if cross linking of the cell wall does not occur in time?

Answer 11

Wall imports water and nutrients, swells and explodes

Question 12

What produces delicious diarrhoea with penicillins?

Answer 12

Exploding bacterial cells

Question 13

Why are penicillins more effective?

Answer 13

It’s the last step to make the cell wall so loads of energy has been expended and wasted

Question 14

Basically structural unit of the cell wall

Answer 14

Muropeptides

A repeating disaccharide liked through a lactyl ether to a tetra peptide.

Question 15

Peptides are cross linked by a …. chain

Answer 15

Pentaglycine

Question 16

Penicillins are more effective against gram positive of negative

Answer 16

Positive
( wall is covered with outer membrane
Where as the negative cell wall is lipopolysaccarides)

Question 17

What is the reactive inhibited by beta lactams?

Answer 17

During cross linking the terminal fifth alanine needs to be split off by enzyme

Question 18

How does beta lactam penetrate the membrane of gram neg bacteria?

Answer 18

Through porin channels

some bacteria may be existent due to smaller ones

Question 19

Four main resistance mechanisms?

Answer 19

Pump it out
Don’t allow it in
Metabolise it
Mutate/change target site

Question 20

What is the difference between Dala and DLac ( when beta lactam mimics DAla?)

Answer 20

OH instead of NH2

No H bond is formed

Question 21

How do porins work to be resistant

Answer 21

Reduce drug access or accumulation(by decreasing permiability)

Question 22

How do pumps work to make resistance? (3)

Answer 22

Increasing active efflux if drugs by Pgp (known as MDR1)
Or
ATP binding cassette sub family B member 1 (ABCB1)
Or
Cluster differentiation 243

Question 23

Three metabolic modes of resistance

Answer 23

1 deactivation of ceph/pen with ß-lactamases
2 hydrolysis of amides to break down anti-folate in folic acid mimetic antibiotics
3 oxidative demethylation with CYP

Question 24

How is MRSA resistant?

Answer 24

Mutation of PBP

Question 25

How does mutation cause resistance?

Answer 25

1 alter target site
2 increase no of possible receptors (diluting effect)
3 alter bio synthetic pathways
4 RNA methylation for RNA binding antibiotics

Question 26

E.g. Of an alteration to a biosynthetic pathway to cause resistacne

Answer 26

Sulfonamide resistance:
Bacteria do not require PABA (precursor for synthesis of folic and nucleic acids) - instead they import extracellular folic acid

Question 27

Antibiotics that form chelates

Answer 27

Tetracyclines
Quinolones (ciprofloxacin)
Rifampicin
Some macrloides

Isoniazid and ethambutol