Antibiotics

Question 1

Describe three possible targets for antibiotics and give two examples for each type. (6)

Answer 1

DNA synthesis - ciprofloxacin, trimethoprim
Protein synthesis - gentamicin, erythromycin
Cell wall synthesis - Beta lactams, vancomycin.

Question 2

Describe two reasons for prescribing antibiotics. (4)

Answer 2

Prophylaxis to prevent bacterial infections - peri-operative, short term (meningitis), long term (asplenia or immunodeficiency).
Therapy of significant bacterial infections - empiric or culture proven treatment.

Question 3

Describe the three things it is important for antibiotic therapy to consider. (3)

Answer 3

Minimal impact on commensalism organisms
Clean kill of infecting bacteria or no resistance in remaining bacteria
No unwanted effects in the patient - no DDIs or toxicities.

Question 4

Describe how you would assess antibiotic activity. (2)

Answer 4

Drug sensitivity disc testing.

The minimum inhibitory concentration required to inhibit the growth of bacteria in vitro.

Question 5

Define a “breakpoint” (2)

Answer 5

MIC and pharmacokinetics of an antibiotic to predict the likely susceptibilities.

Question 6

Describe the two pharmacodynamic approaches to antibiotic therapy. (4)

Answer 6

Time dependent killing - prolonged antibiotic presence at the site of infection, but at low concentrations.
Concentration dependent killing - high antibiotic concentration at site of infection, but a short course.

Question 7

Describe the three types of resistance to antibiotics. (6)

Answer 7

Innate - bacteria has always been resistant to that type of antibiotic.
Acquired - through a mutation of their own DNA
Acquired - through the acquisition of pre-formed resistance genes through horizontal gene transfer.

Question 8

Describe the four mechanisms of resistance. (8)

Answer 8

Antibiotic inactivation - Beta lactamase
Alteration of target site - penicillin binding protein
Reduced intracellular antibiotic accumulation - active efflux or decreased permeability.
Altered metabolic pathways - altering use of folic acid to resist folate acid antagonists.

Question 9

Describe two methods for reducing antibiotic resistance. (2)

Answer 9

Proper antibiotic prescribing

Infection control measures eg washing hands, isolations.

Question 10

Describe 5 adverse effects of antibiotics. Name an example for each ADR. (10)

Answer 10

Allergic reactions - penicillin
Nephrotoxicity - aminoglycosides 
Hepatotoxicity - flucloxicillin
Ototoxicity - aminoglycosides
Bone marrow toxicity - aminoglycosides are nephrotoxic so toxins build up, and this myelosuppresses.

Question 11

Give two examples of Beta Lactamase inhibitors. (2)

Answer 11

Co-amoxiclav

Piperacillin

Question 12

Name one cephalosporin and give an example of one use of the drug. (2)

Answer 12

Ceftriaxone 
Enteric fever (typhoid and paratyphoid)

Question 13

Name an antibiotic with good intracellular penetration. (1)

Answer 13

Erythromycin

Question 14

Name two tetracyclines. (2)

Answer 14

Tetracycline

Doxycycline

Question 15

Name two glycopeptides (2)

Answer 15

Vancomycin

Teicollanin

Question 16

Mechanism of action for trimethoprim. (1)

Answer 16

Inhibits folic acid synthesis.

Question 17

What does co-trimoxazole treat? (2)

Answer 17

PCP Pneumonia

MRSA

Question 18

What do Azoles inhibit?(1)

Answer 18

Cell membrane synthesis.

Question 19

Name one carbapenem. (1)

Answer 19

Meropenem.

Question 20

Describe the treatment for thrush. (1)

Answer 20

Flucanazole.

Question 21

Describe why Beta lactamase inhibitors are useful. (3)

Answer 21

Good action against Gran positive, Gram negative and aerobes.

Question 22

Name one aminoglycoside. (1)

Answer 22

Gentamicin

Question 23

Are penicillins more active against Gram negative or Gram positive?

Answer 23

Positive.

Question 24

Name three penicillins. (3)

Answer 24

Pencillin
Amoxicillin
Flucloxacillin

Question 25

Name one macrolide (1)

Answer 25

Erythromycin

Question 26

What are the constituents of co-trimoxazole? (2)

Answer 26

Trimethoprim

Sulphamethoxazole

Question 27

Describe the mechanism of action of quinolones. (1)

Answer 27

Inhibits DNA gyrase.

Question 28

Describe the contraindications of tetracyclines. (2)

Answer 28

Given to under 12s - bone and teeth staining.

Question 29

What is the main concern when prescribing cephalosporins? (1)

Answer 29

Association with C. Diff.

Question 30

Describe the UHL first line for sepsis. (1)

Answer 30

Meropenem.

Question 31

Describe one use for gentamicin. (1)

Answer 31

Severe Gram negative sepsis

Question 32

Describe the common ADRs for vancomycin, and name one alternative. (2)

Answer 32

Nephrotoxic and ototoxic

Teicoplanin

Question 33

Explain why Ceftriaxone is useful. (1)

Answer 33

Good CSF penetration.

Question 34

Describe the common actions of metronidazole. (2)

Answer 34

Active against anaerobes and Protozoa.

Question 35

Name the 4 Beta lactamase subgroups. (4)

Answer 35

Penicillins (including Beta lactamase inhibitors)
Cephalosporins
Carbapenems
Monobactams.

Question 36

Describe the treatment for C. Diff. (2)

Answer 36

Oral vancomycin.

Question 37

Describe three common uses for tetracyclines. (3)

Answer 37

Penicillin allergy
Atypical Pneumonia
Chlamydia