Antibiotics II

Question 1

What is an example of a carbapenam? What is it used for?

Answer 1

Imipenem.

Broadest of all antibacterials (except MRSA). Used mostly in ICUs where there is a high density of resistant organisms.

Question 2

What is an example of a monobactam? What is it used for?

Answer 2

Aztreonam

Used for: gram (-) aerobic bacilli (ESPECIALLY PSEUDOMONAS). No gram (+) or anaerobes.

Question 3

What is vancomycin used for?

Answer 3

Usually only MRSA, coagulase (-) staph, aminopenicllin-resistant enterococcus, oral utility against metronidazole-resistant C. difficile.

Question 4

What does Daptomycin attack? What is it used for?

Answer 4

Forms a pore in the cell membrane.

Used for gram (+) cocci; used for VRE and VRSA.

Question 5

What is the gram (-) version of Daptomycin? What is it used for?

Answer 5

Colistin.

Usually reserved for Pseudomonas species resistant to all other antibacterials.

Question 6

What is a 1st generation fluoroquinolone? What is its mechanism?

Answer 6

Ciprofloxacin.

Inhibits DNA gyrase at low concentrations.

Question 7

What is ciprofloxacin used for?

Answer 7

All gram (-) enterobactericeae, urinary pathogens resistant/allergic to conventional treatment.

Question 8

What is a 2nd generation fluoroquinolone? What is its mechanism?

Answer 8

Levofloxacin.

Inhibits DNA gyrase at low concentrations, inhibits topoisomerase IV at high concentrations.

Question 9

What is levofloxacin used for?

Answer 9

Same spectrum as 1st generation fluoroquinolones, with the addition of Strep. pneumoniae.

Question 10

What is the mechanism of Metronidazole? What is it used for?

Answer 10

Under anaerobic conditions where there is lots of acid, it is reduced to an active free radical, which damages bacterial and certain protozoal DNA.

It’s used for all anaerobic (drug of choice of C. difficile), some protoxoa, H. pylori.

Question 11

What is the drug of choice for C. difficile?

Answer 11

Metronidazole

Question 12

What is the mechanism of Rifampin? What is it used for?

Answer 12

Inhibits DNA-dependent RNA polymerase to halt RNA transcription

Used for: mycobacterium tuberculosis and staph aureus.

Question 13

What are two aminoglycoside/protein synthesis inhibitors? What are their mechanisms?

Answer 13

Gentamicin, tobramycin.

Inhibits 30S ribosome: forms a tight complex with ribosomal protein, causing codon-anticodon misreading and production of inactive proteins (bactericidal). Also inhibits initiation.

Question 14

What are Gentamicin and Tobramycin?

Answer 14

Extremely effective against gram (-) rods, INEFFECTIVE AGAINST ANAEROBES due to an oxygen-dependent uptake mechanism.

Question 15

What should you not take doxycycline with?

Answer 15

Milk and antacids (inactivates drug)

Question 16

What is a tetracycline/protein synthesis inhibitor? What is its mechanism?

Answer 16

Doxycycline.

Inhibits 30S ribosome: blocks access of tRNA anticodon to its codon.

Question 17

What is doxycycline used for?

Answer 17

Gram (+) (S. pneumoniae and MRSA), very effective against intracellular pathogens (mycoplasma, chlamydia, legionella, rickettsia).

Question 18

What is the mechanism of Clindamycin? What is it used for?

Answer 18

Binds to 50S subunit at “A site”, which blocks peptide bond formation.

Used for all anaerobic bacteria (EXCEPT C. DIFFICILE), utility for pneumococci and MRSA.

Question 19

What is an example of a Macrolide? What is its mechanism?

Answer 19

Azithromycin

Binds to 50S subunit and blocks translocation by interference with tRNA release following peptide bond formation (inhibiting the peptide exit tunnel).

Question 20

What is Azithromycin used for?

Answer 20

Effective for intracellular pthogens (mycloplasma, chlamydia, legionella), H. influenza; utility for Gram (+) organisms

Question 21

What is the mechanism of Linezolid? What is it used for?

Answer 21

Binds to 50S ribosome and inhibits peptidyl transferase.

Gram (+) organisms; used primarily for VRSA and MRSA

Question 22

What do you use for aspiration pneumonia?

Answer 22

Clindamycin.