Anti-bacterials

Question 1

Solutions to Penicillin resistance

Answer 1

1. Produce penicillin analogues that are not as easily recognised by b-lactamase.
   
   • Add bulky side-chains
   • Which acts as ‘steric shield’
2. Administrate penicillin in combination with b-lactamase inhibitors such as Clavulanic acid

Question 2

What are the two ways bacteerial cells can form penicillin resistance

Answer 2

• Synthesis of β-lactamase
• Mutations at transpeptidase

Question 3

How does Penicilllin act on bacteria

Answer 3

It inhibits the pentaglycine link between L-lysine and D-alanine

Question 4

How do bacteria avoid natural proteases in the body

Answer 4

They consist of unnatural stereoisomers of amino acids = Resistant to protease catalysed hydrolysis

Question 5

Why is the b-lactam ring reactive

Answer 5

Because the ring consists of 90 degree bonds and not 120 therefore meaning that there is no SP2 hybridisation resulting in no delocalised resonance that would increase stability.

Question 6

What makes an antibiotic a bacteriocidal and give examples

Answer 6

They inhibit cell wall biosynthesis and therefore water diffuses through.
* Influx of water leads to cell membrane rupturing -> Cell lysis

Question 7

What do sulfonamides do

Answer 7

They inhibit dihydropteroate synthase from producing folic acid thereby inhibiting bacterial growth.

It does NOT kill bacteria

Question 8

What are the important units in a sulfonamide

Answer 8

• Para substituted aryl sulfonamide -> Mimics PABA structure and binds to enzyme
• Primary amine -> Allows for hydrogen bonding and is not too big (secondary/tertiary are too big and wont fit)
• Electron withdrawing unit to deprotonate -> Pyrimidine is a good example

Question 9

Drug that inhibits foli acid biosynthesis

Answer 9

Sulfonamides

Question 10

Drugs that inhibit peptidoglycan cell wall

Answer 10

Penicillins, Cephalosporins

Question 11

Genetic transfer of antibiotic resistance

Answer 11

• Transduction -> Bacterial viruses transfer resitant genes in their DNA plasmids by infecting other cells.
• Conjugation -> Genetic material exhanged directly through a conjugation tube

Question 12

Drugs that target protein synthesis in bacteria

Answer 12

• Macroglides (Erythromycin)
• Chloramphenicol
• Aminoglycosides
• Tetracyclines

Question 13

What do tetracyclines target

Answer 13

Target small 30s ribosomes and selectively bind to them thereby preventing tRNA from binding and inhibiting protein synthesis

Question 14

What do macroglides target

Answer 14

Macroglides target inhibit the translocation step of protein synthesis for bacteria

Question 15

What do Aminoglycosides target

Answer 15

They target the translocation step of protein synthesis

Question 16

Macroglides are not stable under acidic conditions

Answer 16

TRUE

Question 17

What is the Antimicrobial stewardship

Answer 17

A package of measures designed to ensure the optimal selection of therapy for patients for the best clinical outcome while minimising toxicity