Antimicrobials

Question 1

What is the mechanism of action of penicillin?

Answer 1

Bind penicillin-binding proteins (transpeptidases). Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes.

Question 2

What are the clinical uses of penicillin?

Answer 2

Mostly used for gram positive organisms (*S. pneumoniae, S. pyogenes, Actinomyces). *

Also used for gram-negative cocci (N. meningitidis) and spirochetes (*T. pallidum). *

Bactericidal for gram-positive cocci, gram positive rods, gram-negative rods, gram-negative cocci and spirochetes.

Question 3

Name two toxicities of **penicillin. **

Answer 3

Hemolytic anemia

Hypersensitivity reactions

Question 4

What is the mechanism of penicillin resistance?

Answer 4

Penicillinase in bacteria (a type of ß-lactamase) cleaves ß-lactam ring.

Question 5

Name two penicillinase-sensitive penicillins (aminopenicillins).

Answer 5

Ampicillin

Amoxicillin

Question 6

What is the mechanism of action of the aminopenicillins (amoxicillin, ampicillin)?

Answer 6

Bind penicillin-binding proteins (transpeptidases). Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes.

Question 7

What are the clinical uses of the aminopenicillins (amoxicillin, ampicillin)?

Answer 7

Extended spectrum penicillins: H. influenzae, H. pylori, E. coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella, **enterococci. **

HHELPSS kill **enterococci. **

Question 8

Give three toxicities of aminopenicillins.

Answer 8

Hypersensitivity reactions, rash, pseudomembranous colitis.

Question 9

What is the mechanism of resistance for the aminopenicillins?

Answer 9

Penicillinase in bacteria (a type of ß-lactamase) cleaves ß-lactam ring.

Question 10

Name 3 penicillinase-resistant penicillins.

Answer 10

Oxacillin

Nafcillin

Dicloxacillin

Question 11

What is the mechanism of action of the penicillinase-resistant penicillins?

Answer 11

Bind penicillin-binding proteins (transpeptidases). Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes.

Question 12

What makes dicloxacillin, nafcillin, and oxacillin penicillinase-resistant?

Answer 12

These drugs have a bulky R group that blocks access of the ß-lactamase to the ß-lactam ring.

Question 13

What is the clinical use of the penicillinase-resistant penicillins (dicloxacillin, nafcillin, oxacillin)?

Answer 13

S. aureus

(except MRSA–resistant because of altered penicillin-binding protein sight).

Question 14

Give two toxicities of the penicillinase-resistant penicillins (dicloxacillin, nafcillin, oxacillin).

Answer 14

Hypersensitivity reactions and interstitial nephritis.

Question 15

Name two antipseudomonals.

Answer 15

Ticarcillin

Piperacillin

Question 16

What is the mechanism of action of the antipseudomonals (piperacillin, ticarcillin)?

Answer 16

Bind penicillin-binding proteins (transpeptidases). Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes.

Question 17

What are the clinical uses of piperacillin and ticarcillin?

Answer 17

**Pseudomonas **species and gram-natative rods. (Susceptible to penicillinase–use with ß-lactamase inhibitors).

Question 18

Name a toxicity of the antipseudomonals (piperacillin, ticarcillin).

Answer 18

Hypersensitivity reactions

Question 19

Name three ß-lactamase inhibitors.

Answer 19

Clavulonic Acid

Sulbactam

Tazobactam

Question 20

What is the clinical use of clavulonic acid, sulbactam and tazobactam?

Answer 20

Added to penicillin antibiotics to protect the antibiotic from destruction by ß-lactamase (penicillinase).

Question 21

Which drug can we combine with amoxicillin and ampicillin to protect against destruction by ß-lactamase?

Answer 21

Claculanic acid

Question 22

What drug is the prototype ß-lactam antibiotic?

Answer 22

Penicillin

Question 24

What is the mechanism of action of the cephalosporins?

Answer 24

These are bactericidal ß-lactam drugs that inhibit cell wall synthesis but are less susceptible to penicillinases.

Question 25

Which organisms are generally **not** covered by the cephalosporins?

Answer 25

**LAME: *****L**isteria, ***A**typicals (*Chlamydia, Mycoplasma*), **M**RSA and **E**nterococci. [Exception: ceftaroline covers MRSA]

Question 26

Name two first generation cephalosporins.

Answer 26

Cephalexin Cefazolin

Question 27

What are the clinical uses of the first generation cephalosporins?

Answer 27

Gram-positive cocci: ***P**roteus mirabilis, **E. c**oli, **K**lebsiella pneumoniae* *[**PEcK**]*

Question 28

Which cephalosporin is used prior to surgery to prevent *S. aureus* wound infections?

Answer 28

Cefazolin

Question 29

Name three second generation cephalosporins.

Answer 29

Cefaclor Cefuroxime Cefoxitin

Question 30

What are the clinical uses of the second generation cephalosporins?

Answer 30

Gram positive cocci: ***H**aemophilus influenzae, **E**nterobacter aerogenes, **N**eisseria* spp., ***P**roteus mirabilis, **E.** **c**oli, **K**lebsiella pneumoniae, **S**erratia marcescens*. [**HEN PEcKS**]

Question 31

Name three 3rd generation cephalosporins.

Answer 31

Ceftriaxone Cefotaxime Ceftazidime

Question 32

What are the clinical uses of the third generation cephalosprins?

Answer 32

Serious gram-negative infections resistant to other beta-lactams. Ceftriaxone: meningitis, gonorrhea, disseminated Lyme disease Ceftazidime: *Pseudomonas*

Question 33

Name one fourth generation cephalosporin.

Answer 33

Cefepine

Question 34

What are the clinical uses of cefepime?

Answer 34

Gram negative organisms, with increased activity against *Pseudomonas* and gram-positive organisms.

Question 35

Name a 5th generation cephalosporin.

Answer 35

Ceftaroline

Question 36

What are the clinical uses of ceftaroline?

Answer 36

Broad gram-positive and gram-negative organism coverage, including MRSA. [Exception: does not cover *Pseudomonas*]

Question 37

Cephalosporin toxicities (4)

Answer 37

Hypersensitivity reactions, autoimmune hemolytic anemia, disulfram like reaction, vitamin K deficiency.

Question 38

Name two drug-drug interactions seen with cephalosporins.

Answer 38

Exhibit cross-reactivity with penicillins and increase nephrotoxicity of aminoglycosides.

Question 39

What is the mechanism of resistance to cephalosporins?

Answer 39

Structural change in penicillin-binding proteins.

Question 40

Name four carbapenems.

Answer 40

Imipenem, meropenem, ertapenem, doripenem.

Question 41

What is the mechanism of action of imipenem?

Answer 41

Broad specturm, ß-lactamase-resistant carbapenem.

Question 42

Which drug is always administered with imipenem, and why?

Answer 42

Given with cilastatin (inhibitor of renal dehydropeptidase I) to decrease inactivation of the drug in the renal tubules.

Question 43

What are the clinical uses of the carbapenems?

Answer 43

Gram positive cocci, gram-negative rods and anaerobes. [Wide spectrum but many side effects--limit use to life-threatening infections/after other drugs fail]

Question 44

Carbapenem toxicities?

Answer 44

GI distress, skin rash, and CNS toxicity (seizures) at high plasma levels.

Question 45

Which carbapenem has a lower risk of seizures and is stable to dehydropeptidase I?

Answer 45

Meropenem

Question 46

Name a monobactam antibiotic.

Answer 46

Aztreonam