Antimicrobials

Question 1

Detail the mechanism of action of sulfonamides.

Answer 1

Inhibit folic acid synthesis
Compete with PABA for dihydropteroate synthase
Bacteriostatic

Question 2

Detail the mechanism of action of fluoroquinolones.

Answer 2

Inhibit DNA gyrase

Bactericidal

Question 3

Define an antimetabolite.

Answer 3

A drug, through chemical similarity, inhibits normal cellular metabolism

Question 4

What compound do sulfonamides mimic?

Answer 4

PABA

Question 5

What enzyme is inhibited by trimethoprim?

Answer 5

Dihydrofolate reductase

Question 6

Define sequential blockade.

Answer 6

Combined action of 2 drugs that inhibit sequential steps in a pathway of bacterial metabolism

Question 7

Is the combination of trimethoprim + sulfamethoxazole bactericidal or bacteriostatic?

Answer 7

Bactericidal

Question 8

Trimethoprim-sulfamethoxazole is established to be effective against what opportunistic protozoal infection in an AIDS patient?

Answer 8

Toxoplasmosis

Question 9

What drug class is effective at treating diarrhea caused by gram - pathogens?

Answer 9

Fluoroquinolones

Question 10

List 3 fluoroquinolones.

Answer 10

Ciprofloxacin
Levofloxacin
Moxifloxacin

Question 11

What compounds interfere with fluoroquinolone absorption?

Answer 11

Multivalent cations

Question 12

What effect do fluroquinolones and aminoglycosides have on normal flora after the plasma concentration of the drug has fallen below the minimum inhibitory concentration?

Answer 12

Postantibiotic effects- continued inhibition of bacterial growth

Question 13

What infections are fluroquinolones effective at treating?

Answer 13

Urogenital and GI tract infections due to gram negative organisms

Question 14

What are the major antibiotics that inhibit bacterial wall synthesis?

Answer 14

Penicillins
Cephalosporins
Carbapenems
Monobactams
Vancomycin

Question 15

Define bactericidal.

Answer 15

Kills bacteria

Question 16

Define bacteriostatic.

Answer 16

Does not kill bacteria, but inhibits growth

Question 17

What drug classes are considered beta-lactam antibiotics?

Answer 17

Penicillins
Cephalosporins
Carbapenems

Question 18

Define beta-lactmases.

Answer 18

Bacterial enzymes that hydrolyze the beta-lactam ring of certain beta-lactam antibiotics

Question 19

Define minimal inhibitory concentration.

Answer 19

Lowest concentration of a drug capable of inhibiting growth of an organism

Question 20

Penicillins are polar compounds and are not metabolized extensively; usually, they are excreted in the urine via glomerular filtration and tubular secretion. What drug inhibits the latter process?

Answer 20

Probenecid- used to treat gout

Question 21

Are beta-lactam antibiotics bactericidal or bacteriostatic?

Answer 21

Bactericidal

Question 22

What are inhibitors of bacterial penicillinases?

Answer 22

Clavulanic acid
Sulbactam
Tazobactam

Question 23

What is the mechanism of penicillin resistance responsible for MRSA and PRSP?

Answer 23

Structural changes in PBP

Question 24

Which penicillin is administered parenterally? Which penicillin is administered orally?

Answer 24

Parenterally- Penicillin G

Orally- Penicillin V

Question 25

Penicillin G is clinically useful in the treatment of infections caused by what organisms?

Answer 25

Common streptococci Meningococci Gram positive rods Spirochetes

Question 26

Is penicillin used to treat gonorrhea? Syphilis?

Answer 26

Gonorrhea- no | Syphilis- yes

Question 27

What drugs have a wider spectrum of antibacterial activity than penicillin G, but remain susceptible to penicillinases?

Answer 27

Extended spectrum penicillins- Ampicillin, Amoxicillin | Antipseudomonal penicillins- Piperacillin (adds coverage for gram negatives)

Question 28

What toxicities are associated with the penicillins?

Answer 28

Allergy | GI disturbances

Question 29

Interstitial nephritis is associated with what penicillin?

Answer 29

Methicillin

Question 30

What penicillin is associated with neutropenia?

Answer 30

Nafcillin

Question 31

Penicillin can cause a rash and hemolytic anemia, contrast the hypersensitivity reactions associated with each.

Answer 31

Rash- type 1 | Hemolytic anemia- type 2

Question 32

Detail the mechanism of action of the cephalosporins.

Answer 32

Bind to PBPs- bactericidal

Question 33

Are MRSA strains resistant to cephalosporins?

Answer 33

Yes

Question 34

What are examples of first generation cephalosporins?

Answer 34

Cephalexin (po) | Cefazolin (parenteral)

Question 35

What are examples of second generation cephalosporins?

Answer 35

Cefuroxime | Cefaclor

Question 36

What are examples of third generation cephalosporins?

Answer 36

Ceftriaxone Ceftazidime Cefdinir Cefepime

Question 37

What are examples of fourth generation cephalosporins?

Answer 37

Cefepime | Ceftaroline

Question 38

Sinus, ear, and respiratory infections caused by H. influenzae or M. catarrhalis can be treated with what class of drugs?

Answer 38

Second generation cephalosporins

Question 39

What generation of cephalosporins have good penetration of the BBB?

Answer 39

Third

Question 40

A patient has a history of anaphylaxis to penicillins, can they be treated with a cephalosporin?

Answer 40

No

Question 41

What are examples of carbapenems?

Answer 41

Imipenem | Ertapenem

Question 42

Why is cilastatin given with imipenem IV?

Answer 42

Inhibits dehydropeptidase- enzyme in kidney that degrades imipenem

Question 43

Carbapenems are useful for what types of infections?

Answer 43

Infections caused by organisms resistant to other antibiotics

Question 44

Where does vancomycin bind?

Answer 44

D-Ala-D-Ala terminal of bacterial wall peptidoglycan

Question 45

What confers vancomycin resistance in strains of enterococci and staphylococci?

Answer 45

Replacement of terminal D-Ala by D-lactate

Question 46

Bacitracin inhibits cell wall synthesis in gram-positive organisms, however, it is reserved for topical use, why?

Answer 46

Nephrotoxic

Question 47

Daptomycin is active against vancomycin resistant strains of enterococci and staphylococci, why should creatine phosphokinase me monitored in a patient being treated with this drug?

Answer 47

Daptomycin can cause myopathy

Question 48

A 33-year-old man was seen in a clinic with a complaint of dysuria and urethral discharge of yellow pus. He had a painless clean-based ulcer on the penis and nontender enlargement of the regional lymph nodes. Gram stain of the urethral exudate showed gram-negative diplococci within PMNs. What is the most appropriate treatment of gonorrhea in this patient?

Answer 48

Ceftriaxone IM as single dose

Question 49

You want to start a patient with renal failure on imipenem, why must the dosing be adjusted for this patient?

Answer 49

Imipenem is hydrolyzed by renal dehydropeptidase, in the setting of renal failure toxic levels of the drug can cause CNS toxicity (seizures)

Question 50

What is the mechanism by which pneumococci are resistant to penicillin G?

Answer 50

Changes in chemical structure of penicillin binding protein