1 Intro to antibacterial agents

Question 1

Differentiate between antibiotics and antimicrobial agents

Answer 1

Antibiotics are organically produced by bacteria.

Antimicrobials are antibiotics/synthetic/semi-synthetic compounds that kill organisms.

Question 2

Differentiate between bacteriostatic and bactericidal

Answer 2

Bacteriostatic: inhibits bacterial growth through protein synthesis.
Bactericidal: kills bacteria (cell wall-active agents)

Question 3

Define MIC

Answer 3

Minimum inhibitory concentration: minimum conc of antibiotic at which visible growth is inhibited

Question 4

What is the structure of a bacterial cell wall?

Answer 4

Made of peptidoglycans. These are polymers of NAM (n-acetyl muramic acid) and NAG (N-acetly glucosamine). These are cross-linked by Gly5. Terminal D-ala is lost on cross linking

Question 5

What types of antibiotics are cell wall synthesis inhibitors?

Answer 5

Beta-lactams.

Glycopeptides.

Question 6

What is the structure of B-lactams and how do they work?

Answer 6

Beta lactam ring is analogue of D-alanyl-D-alanine.

Interferes with penicillin binding proteins that cross link peptidoglycans in bacterial cell wall.

Question 7

Name the four classes of beta-lactams.

Answer 7

Penicillins.
Cephalosporins.
Carbapenems.
Monobactams.

Question 8

Explain how glycopeptides work, give one example and explain their activity limitations.

Answer 8

Bind to D-alanyl-Dalanine on NAM, inhibiting cross-linking.
Vancomycin.
Only act on gram+ves as unable to penetrate outer membrane porins.

Question 9

How is protein synthesised in bacteria?

Answer 9

Ribocnucleotin complexes catalyse peptide bond formation and synthesise polypeptides.
50S and 30S units join to form 70S initiation complex.

Question 10

Name the four classes of protein synthesis inhibitors.

Answer 10

Aminoglycosides.
Macrolide’s, Lincosamides, Sterptomycins.
Tetracyclines.
Oxazolidinones

Question 11

How do aminoglycosides work? 1 example.

Answer 11

Bind to 30S. Gentamicin.

Question 12

How do MLS antibiotics work?

Answer 12

Bind to 50S and block exit tunnel.

Question 13

How do tetracyclines work? 1 example.

Answer 13

Bind to 30S and interfere with tRNA binding. Inhibit RNA translation.
Doxytetracycline.

Question 14

How do oxazolidinone work? 1 example.

Answer 14

Binds to 50S preventing 70S formation.

Linezolid.

Question 15

Name the two types of DNA synthesis inhibitors.

Answer 15

Trimethoprim and sulphonamides.

Quinolones and fluoroquinolones.

Question 16

What is co-tramoxizole and how does it work?

Answer 16

Sulphonamides and trimethoprim. Inhibit folate synthesis.

Question 17

How do quinolones and fluoroquinolones work?

Answer 17

Inhibit DNA gyrase and topoisomerase IV. Preventing DNA supercoiling.

Question 18

What is rifampicin and how does it work?

Answer 18

RNA polymerase inhibitor.

Prevents mRNA synthesis.

Question 19

What is daptomycin and how does it work?

Answer 19

Cyclic lipopeptide. Inserts lipophilic tail into membrane, depolarising it.

Question 20

What are the specific adverse effects of ahminoglycosides, beta-lactams and linezolid?

Answer 20

Amino- reversible renal impairment.
Beta- allergic reactions.
Linezolid - bone marrow depression

Question 21

Which antibiotics are safe to use in penicillin allergy?

Answer 21

Non-severe: cephalosporins and carbapenems.

Any: aztreonam

Question 22

Which antibiotics commonly precipitate a C.diff infection?

Answer 22

Cephalosporins.
Ciprofloxacin.
Clindamycin.

Question 23

What is empiric therapy?

Answer 23

Best guess at antibiotics based on local policies and predicted susceptibility.

Question 24

Which antibiotics have good availability in CSF?

Answer 24

Beta lactams.

Question 25

Which antibiotics have good availability in urine?

Answer 25

Trimethoprim.

Beta-lactams.

Question 26

What are the pharmacodynamic considerations for antibiotic prescription?

Answer 26

Conc dependant. Intermittent high dose. Amino glycosides.

Time dependant. Frequent dose. Beta-lactams

Question 27

Which synergistic combination of antibiotics is used for streptococcal endocarditis?

Answer 27

B lactams and aminoglycosides.

Question 28

Name a cephalosporin.

Answer 28

Cefuroxime.

Question 29

Name a carbapenem.

Answer 29

Meroprenem.

Question 30

Name a monobactam.

What is it’s activity limitation?

Answer 30

Aztreonam.

Gram -ve only.

Question 31

Two examples of MLS antibiotics.

Answer 31

Erythromycin. Clindamycin.

Question 32

Name a quinolone.

Answer 32

Ciprofloxacin.

Question 33

Which antibiotics have poor availability in CSF?

Answer 33

Aminoglycosides.

Vancomycin.

Question 34

Which antibiotics have poor availability in urine?

Answer 34

MLS.

Question 35

What is the spectrum of activity of daptomycin?

Answer 35

Only effective in g+ves.

Question 36

How does trimethoprim work?

Answer 36

Binds to dihydrofolate reductase - preventing folate synthesis.

Question 37

How do sulfonamides work?

Answer 37

Binds to dihydropteroate synthetase - preventing folate synthesis.

Question 38

What type of allergic reactions can β-lactams cause?

Answer 38

Intolerance: nausea, diarrhoea.
Minor skin rash.
Anaphylaxis, urticaria, angio-oedema, bronchospasm, Stevens-Johnson syndrome.

Question 39

What is flucloxacillin commonly used for?

Answer 39

Staph aureus.

Question 40

What is benzylpenicillin commonly used for?

Answer 40

Strep pyogenes.

Question 41

What are cephalosporins commonly used for?

Answer 41

Gram -ve bacilli.

Question 42

What is vancomycin commonly used for?

Answer 42

Gram positives (MRSA).

Question 43

What is metronidazole commonly used for?

Answer 43

Anaerobes.