Notes on Roy's Antimicrobials Slides

Question 1

Penicillins not inactivated by Staphylococcal beta-lactamases

Answer 1

Flucloxacillin, dicloxacillin

Question 2

Is flucloxacillin effective against MRSA?

Answer 2

No

Question 3

Differing spectrum among 1st-4th generations of cephalosporins

Answer 3

1st generation are effective against G+ bacteria.
As generations increase, G+ spectrum decreases and G- spectrum increases.
As generations increase, beta-lactamase resistance increases

Question 4

Bacterial groups resistant to all cephalosporins
1)
2)
3)

Answer 4

1) MRSA
2) Enterococci
3) Bacteroides fragilis

Question 5

Antimicrobials used to treat bacterial meningitis

Answer 5

3rd generation cephalosporins.

These have excellent CSF penetration

Question 6

Anti-pseudomonal antimicrobials

Answer 6

Ticarcillin, piperacillin

Question 7

Spectrum of flucloxacillin, dicloxacillin

Answer 7

Narrow. Anti-Staphylococcal

Question 8

Amoxycillin, ampicillin spectra

Answer 8

Broad spectrum, but beta-lactamase susceptible

Question 9

Common targets of amoxycillin and ampicillin

Answer 9

G- rods.
Enterococci.
Listeria

Question 10

Carbapenems

Answer 10

Very broad-spectrum beta lactams.

Given parenterally

Question 11

Main use of aminoglycosides

Answer 11

G- infections

Question 12

Example of a G- bacterium that aminoglycosides are ineffective against

Answer 12

Salmonella, as this is an intracellular pathogen

Question 13

Toxicity of aminoglycosides

Answer 13

High.

Nephro-, ototoxic

Question 14

Streptomycin

Answer 14

Aminoglycoside, rarely used today except for TB (rarely)

Question 15

Gentamycin and tobramycin

Answer 15

Aminoglycosides.

Wide G- spectrum.

Question 16

Amikacin

Answer 16

Aminoglycoside.

Broader spectrum than gentamycin, but more expensive

Question 17

Quinolones

Answer 17

Bactericidal

Inhibit topoisomerase II, which allows transcription and translation.

Question 18

Anti-Pseudomonas quinolone

Answer 18

Ciprofloxacin

Question 19

Caution with use of quinolones

Answer 19

Animalstudies indicate that they can damage growing joints, so care when prescribing to children

Question 20

Macrolides

Answer 20

Large lactone ring
Binds 50S subunit of RNA, preventing ribosomal translocation.
Bacteriostatic, but can be bacteriocidal at high concentrations.

Question 21

What are macrolides used for?

Answer 21

G+ cocci.

Intracellular pathogens such as TB, chlamydia, legionella.

Question 22

Examples of macrolides

Answer 22

Erythromycin, azythromycin

Question 23

Chloramphenicol

Answer 23

Inhibits peptidyl transferase activity of bacterial ribosome, preventing chain elongation.
Quite toxic.
Used to treat Salmonella typhi

Question 24

Trimethoprim

Answer 24

Dihydrofolate reductase inhibitors.
Affinity for bacterial dihydrofolate reductase is several thousand times that of human.
DFR involved in formation of thymidine from folate.
Interferes with DNA synthesis

Question 25

Tetracyclines

Answer 25

Bind reversibly to 30S ribosome subunit.

Blocks binding of aminoacyl tRNA to ribosome binding site.

Question 26

What is metronidazole used to treat?

Answer 26

C. difficile.

Protozoal infections