Micro - Antimicrobials (Penicillins)

Question 1

What are the major forms of Penicillin? Into what broader class of antibiotics are Penicillins classified?

Answer 1

Penicillin G (IV and IM form); Penicillin V (oral); Prototype Beta-lactam antibiotics.

Question 2

What is the mechanism of Penicillin? More specifically, list the 3 major components of its mechanism of action.

Answer 2

(1) Bind penicillin-binding proteins (transpeptidases) (2) Block transpeptidase cross-linking of peptidoglycan (3) Activate autolytic enzymes

Question 3

What is Penicillin mostly used for clinically? What are its other clinical uses?

Answer 3

Mostly used for gram-positive organisms (S. pneumoniae, S. pyogenes, Actinomyces); Also used for Neisseria meningitidis and Treponema pallidum

Question 4

What enzyme is particularly relevant to Penicillin, and what is the impact of this enzyme?

Answer 4

Penicillin is not penicillinase resistant

Question 5

Against what kinds of bacteria is Penicillin bactericidal?

Answer 5

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

Question 6

What 2 toxicities are associated with Penicillin?

Answer 6

(1) Hypersensitivity reactions (2) Hemolytic anemia

Question 7

What kind of resistance should be considered with Penicillin?

Answer 7

Penicillinase (a type of Beta-lactamase) cleaves Beta-lactam ring

Question 8

What type of Penicillin are oxacillin, nafcillin, and dicloxacillin?

Answer 8

Penicillinase-resistant penicillins

Question 9

What are 3 examples of Penicillinase-resistant Penicillins?

Answer 9

(1) Oxacillin (2) Nafcillin (3) Dicloxacillin

Question 10

Again, what are the penicillinase-resistant penicillins? What is their mechanism of action and spectrum?

Answer 10

Oxacillin, Nafcillin, Dicloxacillin; Same as penicillin (i.e., block peptidoglycan cross linking), Narrow spectrum

Question 11

Are oxacillin, nafcillin, and dicloxacillin penicillinase-resistant? Why or why not?

Answer 11

Yes; Penicillinase resistant because bulky R group blocks access of Beta-lactamase to Beta-lactam ring

Question 12

For what are penicillinase-resistant penicillins (i.e., oxacillin, nafcillin, dicloxacillin) clinically used?

Answer 12

S. aureus (except MRSA; resistant because of altered penicillin-binding protein target site); Think: “Use NAF (Nafcillin) for STAPH”

Question 13

What are the 2 toxicities associated with penicillinase-resistant penicillins (i.e, oxacillin, nafcillin, dicloxacillin)?

Answer 13

(1) Hypersensitivity reactions (2) Interstitial nephritis

Question 14

What are the aminopenicillins?

Answer 14

(1) Ampicillin (2) Amoxicillin

Question 15

What kind of drugs are Ampicillin and Amoxicillin?

Answer 15

Aminopenicillins

Question 16

What is the mechanism of action for Aminopenicillins (i.e., Ampicillin and Amoxicillin) and spectrum?

Answer 16

Same as penicillin (i.e., block peptidoglycan cross linking), Wider spectrum; Think: “AMinoPenicillins are AMP-ed up penicillin”

Question 17

Are Aminopenicillins pencillinase resistant?

Answer 17

No, Penicillinase sensitive

Question 18

What are Aminopenicillins combined with for therapy, and why?

Answer 18

Also combine with cavulanic acid to protect against Beta-lactamase

Question 19

Compare of the oral bioavailability of the Aminopenicillins.

Answer 19

AmOxicillin has greater Oral bioavailability than ampicillin

Question 20

How are Aminopenicillins used clinically?

Answer 20

Extended-spectrum penicillin - Haemophilus influenzae, E. coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella, enterococci; Think: Coverage: “ampicillin/amoxicillins HELPSS kill enterococci”

Question 21

What 3 toxicities are associated with Aminopenicillins?

Answer 21

(1) Hypersensitivity reactions (2) Rash (3) Pseudomembranous colitis

Question 22

What is important to note with regard to resistance of Aminopenicillins?

Answer 22

Penicillinase sensitive; Penicillinase (a type of Beta-lactamase) cleaves Beta-lactam ring

Question 23

What are 2 of the Antipseudomal penicillins?

Answer 23

(1) Ticarcillin (2) Piperacillin

Question 24

What kind of drugs are Ticarcillin and Piperacillin?

Answer 24

Antipseudomonal Penicillins

Question 25

What is the mechanism of action of Antipseudomonal Penicillins? What is their spectrum?

Answer 25

Same as penicillin (i.e., block peptidoglycan cross linking), Extended spectrum

Question 26

How are Antipseudomonal Penicillins (e.g., Ticarcillin, Piperacillin) used clinically?

Answer 26

Pseudomonas spp. and gram-negative rods

Question 27

Are Ticarcillin and Piperacillin resistant to penicillinase?

Answer 27

No; Susceptible to penicillinase;

Question 28

What is combined with Antipseudomonal Penicillin therapy, and why?

Answer 28

Use with Beta-lactamase inhibitors (e.g., clavulanic acid); Antipseudomonal Penicillins are susceptible to penicillinase

Question 29

What toxicity is associated with Antipseudomonal Penicillins (i.e., Ticarcillin, Piperacillin)?

Answer 29

Hypersensitivity reactions

Question 30

What are examples of Beta-lactamase inhibitors?

Answer 30

Include Clavulanic Acid, Sulbactam, Tazobactam; CAST

Question 31

What is the clinical use for clavulanic acid, sulbactam, and tazobactam?

Answer 31

Beta-lactamase inhibitors; Often added to penicillin antibiotics to protect the antibiotic from destruction by Beta-lactamase (penicillinase)