Antibiotics IV

Question 1

What are the 3 drug classes that inhibit bacterial nucleic acid synthesis?

Answer 1

1. Fluoroquinolones
2. Rifampin
3. Metronizadole

Question 2

What is the first generation FQ? Mechanism?

Answer 2

Ciprofloxacin; Inhibit DNA gyrase

Question 3

What is the 2nd generation FQ? Mechanism?

Answer 3

Levofloxacin; Inhibit gyrase and bacterial topoisomerase IV

Question 4

Why are FQs typically well-tolerated?

Answer 4

Humans don’t have DNA gyrase and therefore the drugs are well-tolerated

Question 5

What additional spectrum is added in 2nd generation FQs?

Answer 5

Streptococcus pneumoniae

Question 6

Adverse SEs of FQs

Answer 6

• Allergy
• Second Generation FQs may cause polymorphic ventricular tachycardia (Torsades de Pointes)

Question 7

MOA of rifampin?

Answer 7

Inhibition of DNA-dependent RNA polymerase to stop the replication of RNA from the daughter DNA strand

Question 8

Adverse SEs of Rifampin?

Answer 8

• Allergy
• Possible centrolobular hepatitis when used with isonazid

Question 9

AB spectrum of rifampin?

Answer 9

• Mycobacterium tuberculosis
• Staphylococcus aureus

Question 10

What is the MOA of Metronidazole?

Answer 10

Prodrug that is activated in an anaerobic environment to a drug that is toxic to nucleic acids

Question 11

Adverse SE of Metronidazole?

Answer 11

• Allergy
• Inhibits aldehyde dehydrogenase to cause profound vasodilation and tachyarrhythmias due to the accumulation of acetyl aldehyde when metronidazole is taken with ethanol

Question 12

What is the AB spectrum of metronidazole?

Answer 12

• Anaerobic bacteria such as Clostridium difficile
• Selected Protozoa (Entamoeba histolytica, Giardia lamblia)

Question 13

What are the 30S ribosome inhibitors?

Answer 13

1. Aminoglycosides (gentimicin, tobramycin)
2. Tetracyclines (Doxycycline)

Question 14

What are the 50S Ribosome inhibitors?

Answer 14

1. Macrolides (azithromycin)
2. Linezolid

Question 15

What is the mechanism of gentamicin?

Answer 15

The aminoglycoside binds to the 30S ribosome which causes the transfer of the incorrect amino acyl transfer RNA and hence the wrong amino acid

Question 16

To what bugs are aminoglycosides restricted? Why?

Answer 16

Aerobic or facultative aerobic Gram (-) rods; To enter cells, AGs must be uptaken by an oxygen dependent method

Question 17

What is important about the administration of AGs?

Answer 17

They have rapid lethality and superior prolonged AB effect on Gram (-) rods

Question 18

What is the spectrum of AGs?

Answer 18

Gram negative rods (Enterobacteriacaie) because of ESBL and Carbapenemase-producing strains of Enterobacter cloacae; Furthermore, FQs, 3rd gen cephs. and ES penicillins have promoted resistance

Question 19

What is an important consideration in AG administration in regards to SEs?

Answer 19

While AGs are nephrotoxic, they are only nephrotoxic when they accumulate in the kidney. Therefore, nephrotoxicity is not observed if use is < 48hrs

Question 20

When is AG (gentamicin) use most efficacious?

Answer 20

W/i first 12-24 hrs after exposure

Question 21

What is the MOA for Doxycycline?

Answer 21

Tetracycline that blocks the access of the tRNA anticodon to its codon

Question 22

What is the AB spectrum of tetracyclines?

Answer 22

Doxycycline is effective for intracellular pathogens (mycoplasma, chlamydia, legionella, rickettsia); Gram (+) organisms (S. pneumoniae, MRSA) in face of resistance to lactams

Question 23

Adverse SEs of doxycycline?

Answer 23

• Allergy
• Photosensitivity RXN
• Not orally bioavailable when administered w/ di/tri-valent cations due to chelation

Question 24

MOA for azithromycin?

Answer 24

Macrolide that prevents the release and removal of the “naked” transfer RNA from the “A” site into the cytoplasm (inhibits transolcation by inhibiting translocase enzyme)

Question 25

Spectrum of Azithromycin?

Answer 25

Effective for intracellular pathogens (mycoplasma, chlamydia, legionella), H. influenzae, Gram (+) organisms [pneumococci, MRSA] that have lactam resistance

Question 26

Adverse SEs of Macrolides?

Answer 26

* allergy * GI distress with oral administration * Potential of Torsades de pointes

Question 27

What is the most likely method of AB resistance for azithromycin or doxycycline?

Answer 27

Methylation of the target site or efflux pump

Question 28

MOA of Linezolid?

Answer 28

Inhibit transfer of the peptide chain from the "A" site to the P" site via the inhibition of the peptidyl transferase

Question 29

Spectrum of Linezolid?

Answer 29

Gram (+) organisms; It was primarily developed for infections of MRSA and VRSA

Question 30

Adverse Rxns to Linezolid?

Answer 30

* Allergy * Agranulocytosis with prolonged use

Question 31

MOA of clindamycin?

Answer 31

Inhibit incorporation of new AA into growing peptide chain

Question 32

Clindamycin spectrum?

Answer 32

All anerobes **except C. difficile**, pneumococci and MRSA in face of lactam resistance

Question 33

Adverse effects of Clindamycin?

Answer 33

* allergy * AB most closely associated with C. difficile colitis