Antibiotics

Question 1

What are the 4 classes of beta-lactams?

Answer 1

Penicillin
Cephalosporin
Monobactam
Carbapenam

Question 2

How do beta-lactams function?

Answer 2

Transpeptidases catalyse cross-linking of peptidoglycan in cell walls.

Beta-lactams inhibit these enzymes.

Question 3

How can beta-lactams still be effective against resistant bacteria?

Answer 3

Combine the beta-lactam with beta-lactmasae inhibitors.

Question 4

What does rifamycin do?

Answer 4

Inhibits mRNA production in bacteria.

Question 5

What does daptomycin do?

Answer 5

Inserts itself into bacterial membrane, causing depolarisation and cell destruction.

Question 6

What is meant by ‘Minimum Inhibitory Concentration’?

Answer 6

The minimum concentratio of antibiotic required to inhibit visible growth of bacteria in-vitro.

Question 7

What are 4 mechanisms of antibiotic resistance?

Answer 7

1. Active removal of antibiotic from cell (efflux pumps)
2. Inhibition of entry to target site (decreased permeability of membrane)
3. Production of enzymes that destroy antibiotics (e.g. beta-lactamases)
4. Alteration of target

Question 8

Why isn’t penicillin effective against staphylococcus aureus anymore?

Answer 8

Produces beta-lactamases.

Question 9

What makes MRSA resistant to antibiotics?

Answer 9

Beta-lactam drugs target PBP2, a transpeptidase responsible for peptidoglycan cross-linking.

Some strains of S aureus have a mutated gene that codes for PBP2a, a variant of the transpeptidase that isn’t inhibited by beta-lactams.

Question 10

Aside from pencillinases, what else can beta-lactam resistant bacteria produce?

Answer 10

Cephalosporinases

Carbapenemases

Question 11

What are three penicillinase resistant antibiotics?

Answer 11

Methicillin
Flucloxacillin
Dicloxacillin

Question 12

What are two examples of combining beta-lactams with beta-lactamase inhibitors?

Answer 12

AMoxycillin (antibiotic) + clavulanic acid (inhibitor) = Augmentin

Piperacillin (antibiotic) + tazobactam (inhibitor) = Tazocin

Question 13

What antibiotic is recommended in a patient with a penicillin allergy?

Answer 13

Azithromycin.

Question 14

What is the difference between amoxycillin and pencillin?

Answer 14

Amoxycillin has greater activity against Gram negative bacteria

Question 15

What is the relationship between cephalosporins and enterococci?

Answer 15

Enterococci are all resistant to cephalosporins.

Question 16

How does activity against gram positive/negative change with generations of cephalosporins?

Answer 16

As we increase generations, Gram negative activity increases.

Gram positive activity decreases to the 3rd generation and then picks up to the 5th.

Question 17

What is ampC beta-lactamase production ?

Answer 17

Makes cephalosporinases.

Question 18

What is ESBL?

Answer 18

Extended spectrum beta-lactamase production.

ESBL genes are found on plasmids, meaning they can be easily transferred between bacteria.

Question 19

What are aminoglycosides good for treating? Give an example med

Answer 19

Potent against Enterobacteriaceae and Pseudomonas aeruginosa.
Example - Gentamicin

Question 20

What is the issue with using aminoglycosides such as gentamicin?

Answer 20

Very toxic.

Question 21

What is used to treat Neisseria gonorrhoeae?

Answer 21

IMI ceftriaxone

Question 22

What is used to treat Chlamydia trachomatis?

Answer 22

Azithromycin