Antibiotics (Exam V)

Question 1

What are general properties of antimicrobial agent (5)?

Answer 1

1. Selective Toxicity - bactericidal (kills) or bacteriostatic (slow growth)
2. Spectrum of Activity - what types of organism (gram positive, gram negative, wide, narrow)
3. Modes of Action
4. Side Effects
5. Resistance of Microorganisms

Question 2

What are the 5 main modes of action with ABX and given examples. Essay Questions

Answer 2

1. Inhibition of cell wall synthesis (gram +): PCN, bacitracin, cephalosporin, vancomycin)
2. Disruption of cell membrane function (gram -): polymyxin
3. Inhibition of protein synthesis (broadest group): Tetracycline, erythromycin, streptomycin, chloramphenicol
4. Inhibition of Nucleic Acid synthesis: Rifamycin (transcription), Quinolones (DNA replication), Flagyl
5. Block folic acid synthesis and inhibit metabolism: sulfanilamide, trimethoprim, Bactrim

Question 3

Name two beta-lactamase inhibitors?

Why are beta-lactamase inhibitors sometimes given with PCN?

Answer 3

Clavulanic Acid
Sulbactam

Some bacterias can produce an enzyme call beta-lactamase which breaks the beta lactam ring of PCN.

By giving drugs like Sulbactam and Clavulanic Acid, the drug combo will result in bacteria’s sensitivity to penicillin.

Question 4

What structure is highlighted in red below?

What two antibiotic have this structure?

What type bacteria will these drugs act on?

Answer 4

β-lactam ring

Penicillin and Cephalosporin

Gram (+) cocci and Anaerobes

Question 5

How do β-lactam containing ABX’s inhibit cell wall synthesis?

Answer 5

• The β-lactam ring binds to enzymes that cross link the peptidoglycans that form the wall.

Question 6

What drug is indicated by 1 on the figure below?

Answer 6

Penicillin

Question 7

What drug is indicated by 2 on the figure below?

Answer 7

Cephalosporin

Question 8

What type of bacteria do cell wall inhibitors work best on?

What type of bacteria do cell membrane disruptors work best on?

Answer 8

Gram +

Gram -

Question 9

What are allergic reactions to PCN/Cephalosporins (5)?

Answer 9

1. Anaphylactic shock (0.05%)
2. Skin Rash (<1%)
3. Oral Lesions
4. Hemolytic Anemia
5. Interstitial nephritis

Question 10

What is the most common drug allergy that exists?

Answer 10

• Penicillin allergy (urticaria, redness, etc.)
• Can cross react with similar abx

Question 11

What is an alternative to PCN?
Why?

Does it have better activity on gram positive bacteria?

Answer 11

Cephalosporins
Cephalosporins are more resistant to b-lactamase.
Cephalosporins have a broader spectrum.
Cephalosporins have less allergies than PCN.

First Gen Cephalosporins have better gram (+) activity.
Used for UTI and Staph

Question 12

What drug is good alternative for penicillin resistant gram + bacteria (MRSA)? This is also the drug of last resort.

Answer 12

• Vancomycin (resistant to beta-lactamase)

Question 13

What adverse reactions can occur from vancomycin (10% adverse reaction)?

Answer 13

• “Red-neck” Syndrome - neck flushing from histamine release
• Ototoxicity
• Nephrotoxicity
• Chills/fever

Question 14

How do cell membrane disruptors work?

What is polymyxins effective against?

Answer 14

• Act as detergents essentially. Bind to phospholipids in membrane & create pores.

Very effective against gram (-) bacteria

Question 15

How do tetracyclines work?

Pharmacokinetics of tetracyclines?

Answer 15

They inhibit protein synthesis (bacteriostatic)

Readily absorbed and widely distributed.

Question 16

What drug class/antibiotic has the widest spectrum of activity?

What is the downside of this?

Why are tetracyclines not given to children?

Answer 16

Inhibition of Protein Synthesis (Tetracycline)

Tetracycline will destroy the normal intestinal microbiota and often produce severe GI disorders- bone deposition disorder.

Abnormal bone development

Question 17

What kind of structure do tetracyclines have?
Are they bacteriostatic or bactericidal?

Answer 17

• 4-ring structure
• Bacteriostatic

Question 18

Name the three macrolides discussed in lecture.

What advantage does one have over the other?

Spectrum covered with Macrolides?

Answer 18

-Erythromycin
-Azithromycin
-Clarithromycin

Azithromycin has a 4-5 day antibiotic course

Spectrum: (+), (-), atypicals

Question 19

What drug, discussed in lecture, binds to bacterial RNA polymerase?

Answer 19

• Rifamycin

Question 20

How do Fluoroquinolones work?

What characteristics do these drugs have?

Types and Uses of Quinolones?

Answer 20

Inhibition of DNA gyrase (enzyme that unwinds the DNA)

Excellent gram - activity
Good gram + activity

Types: Cipro, Levaquin, Floxin
Uses: UTI, Resp tract infections, bone, joint infections

Question 21

What compound is needed to make folic acid?

What drug looks like this compound?

Answer 21

PABA

Sulfonamides

Question 22

Which drugs are inhibitors of folic acid synthesis/ antimetabolite?

Answer 22

• Sulfonamides and Trimethoprim

Question 23

What is the mechanism of action of bacterial folic acid synthesis inhibitors?

Answer 23

• Prevent conversion of PABA into DHF (dihydrofolic acid) → → folic acid.

Question 24

What are sulfonamides often used for?
What are they often used with?

Answer 24

• Pneumocystitis & toxoplasmosis
• Often paired with Trimethoprim