28 - 186 - SYSTEMIC AND TOPICAL ANTIBIOTICS

Question 1

first line options for empiric therapy for mild and moderate nonpurulent SSTIs

Answer 1

β-Lactam antibiotics (penicillins and cephalosporins) and clindamycin

Question 2

tetracycline interfere with bacterial protein synthesis by binding to what ribosomal subunit?

Answer 2

30s

Question 3

lincosamides (clindamycin), macrolides, streptogramins, and oxazolidinones interfere with bacterial protein synthesis by binding to what ribosomal subunit?

Answer 3

50s

Question 4

this classification of penicillin are susceptible to β-lactamases and thus have a narrow spectrum of activity

Give an example of this class.

Answer 4

Natural penicillins

Penicillin G

• Administered parenterally, penicillin G is active against Streptococcus spp., Clostridium spp., spirochetes, Pasteurella multocida, Eikenella corrodens, Erysipelothrix rhusiopathiae, and nonβ-lactamase producing staphylococci.

Question 5

Aminopenicillins are oral agents with a broad spectrum of activity.

Give examples of this classification

Answer 5

ampicillin, amoxicillin

• they are still susceptible to β-lactamase, have** limited activity against staphylococci and enteric organisms,** and lack activity against Pseudomonas
• commonly used for community-acquired infections of the upper airway and head and neck (bronchitis, sinusitis, otitis).

Question 5

It is the treatment of choice for all Treponema pallidum infections

Answer 5

Penicillin G

Penicillin V is adminstered orally, is less potent than penicillin G, and is indicated for minor infections

Question 6

examples of Extended-spectrum penicillins

Answer 6

• carboxypenicillins (carbenicillin, ticarcillin)
• ureidopenicillins (piperacillin)

• broad spectrum and susceptibility to β-lactamase
• Carboxypenicillins have some activity against Pseudomonas spp. and Proteus spp.
• They are often administered concomitantly with aminoglycosides for serious pseudomonal infections
• ureidopenicillins, derived from ampicillin with similar Gram-positive coverage, have greater activity against Gram-negative organisms including Pseudomonas
• Amoxicillin, ticarcillin, and piperacillin are often combined with β-lactamase inhibitors (tazobactam, clavulanic acid, sulbactam) to increase activity against Staphylococcus aureus.

Question 7

• examples of antistaphylococcal penicillins

Answer 7

oxacillin, dicloxacillin, nafcillin

• β-lactamase resistant with good activity against S. aureus, but without activity against enterococci or Gram-negative organisms.

Question 8

drug of choice for methicillin-sensitive S. aureus SSTIs and are a good empiric therapeutic choice for **mild nonpurulent SSTIs **such as cellulitis where community-acquired MRSA is not suspected

Answer 8

antistaphylococcal penicillins (oxacillin, dicloxacillin, nafcillin)

Question 9

pregnancy category of penicillins

Answer 9

category B

Question 10

Indications for Penicillin Therapy

Answer 10

Question 11

**Increased penicillin **levels are associated in with what drugs?

Answer 11

probenecid and disulfiram

Question 12

**Enhanced effect **of penicillin is observed if combined with what drugs?

Answer 12

methotrexate and warfarin

Question 13

Contraindications and Precautions of Penicillin Therapy

Answer 13

Question 14

most common adverse events reported with penicillins with manifestations ranging from mild to severe

Answer 14

Hypersensitivity reactions

Question 15

leading cause of drug-induced anaphylaxis

Answer 15

penicillin

Question 16

Question 17

1st generation cephalosporins and their coverage

Answer 17

• cephalexin, cefadroxil, and the parenteral agent cefazolin
• good activity against methicillin-sensitive S. aureus and Streptococcus spp. with limited activity against Gram-negative organisms such as Escherichia coli and Klebsiella spp.

Question 18

Second-generation cephalosporins and their coverage

Answer 18

• **cefprozil, cefaclor, cefuroxime axetil, **and the parenteral agents cefotetan, cefoxitin, and cefuroxime
• expanded Gram-negative activity over the first-generation agents, namely Haemophilus influenzae and Moraxella catarrhalis

Question 19

Third-generation cephalosporins and their coverage

Answer 19

• cefdinir and the parenteral agents cefotaxime, ceftriaxone, and ceftazidime.
• Gram-negative coverage is expanded with the third generation but less effective against Gram-positive organisms.

Question 20

These 3rd gen cephalosporines cross the bloodbrain barrier; as such, they are effective treatment for meningitis caused by H. influenzae, Neisseria meningitidis, and penicillin-sensitive Streptococcus pneumoniae

Answer 20

Cefotaxime and ceftriaxone

Question 21

This 3rd gen cephalosporin is active against Pseudomonas aeruginosa

Answer 21

Ceftazidime

Question 22

This 3rd gen cephalosporin is useful in the treatment of SSTIs because of its activity against** S. aureus and Streptococcus spp.**

Answer 22

Cefdinir

Question 23

Fourth-generation cephalosporins and their coverage

Answer 23

* cefepime * increased activity against Gram-positive bacteria compared to third-generation cephalosporins * active against Gram-negative bacteria such as **Pseudomonas**, **Enterobacteriaceae**, **Neisseria**, and** H. influenzae** but has greater activity against Gram-negative organisms that produce extended spectrum β-lactamase

Question 24

Fifth-generation cephalosporin and its coverage

Answer 24

* ceftaroline * given parenterally with broad-spectrum activity against Gram-positive organisms, including MRSA, resistant S. pneumoniae, and Gram-negative organisms such as H. influenzae and M. catarrhalis, but **not P. aeruginosa.** * indicated for the use of complicated SSTIs, including those caused by MRSA and is an option for empiric therapy for severe purulent SSTIs

Question 25

pregnancy category of cephalosporins

Answer 25

B

Question 26

Pregnancy category of tetracyclines

Answer 26

D

Question 27

Pregnancy category of fluoroquinolones

Answer 27

C

Question 28

Pregnancy category of Trimethoprim - sulfamethoxazole

Answer 28

D

Question 29

Pregnancy category of Lincosamides (clindamycin)

Answer 29

B

Question 30

Indications of Cephalosporin Therapy

Answer 30

Question 31

Contraindications and Precautions of Cephalosporin Therapy

Answer 31

Question 32

Indications for Tetracycline Therapy

Answer 32

Question 33

Contraindications and Precautions of Tetracycline Therapy

Answer 33

Question 34

lincosamide antibiotic derived through chemical modification of lincomycin

Answer 34

Clindamycin

Question 35

Indications for Clindamycin Therapy

Answer 35

Question 36

Contraindications and Precautions of Clindamycin Therapy

Answer 36

Question 37

life threatening complications that may occur in clindamycin therapy

Answer 37

C. difficile-associated diarrhea and pseudomembranous colitis

Question 38

macrolide with highest to least activity against Gram-positive pathogens

Answer 38

**clarithromycin** > erythromycin > azithromycin

Question 40

most active macrolide against Mycobacterium leprae

Answer 40

Clarithromycin ## Footnote * used for skin infections with several other nontuberculous mycobacteria, notable Mycobacterium chelonae, Mycobacterium abscessus, and Mycobacterium fortuitum.

Question 41

pregnancy category of Clarithromycin and erythromycin and azithromycin

Answer 41

* Clarithromycin - C * Erythromycin and azithromycin - B

Question 42

Indications for Macrolide Therapy

Answer 42

Question 43

Contraindications and Precautions of Macrolide Therapy

Answer 43

Question 44

They inhibit the action of bacterial **topoisomerase II (DNA gyrase) and topoisomerase IV**, leading to disruption of DNA replication, transcription, and repair What is the primary target in G(+) and G(-) organisms?

Answer 44

Fluoroquinolones * Gram-positive: topoisomerase IV * Gram-negative: topoisomerase II

Question 45

Ciprofloxacin is most active against what bacteria?

Answer 45

P. aeruginosa

Question 46

Indications for Fluoroquinolone Therapy

Answer 46

Question 47

Contraindications and Precautions of Fluoroquinolone Therapy

Answer 47

Question 49

They work synergistically to inhibit bacterial nucleic acid synthesis by i**nhibiting dihydrofolate reductase** and **dihydropteroate synthetase**

Answer 49

Trimethoprim-sulfamethoxazole (cotrimoxazole, TMPSMX) ## Footnote inhibiting dihydrofolate reductase (trimethoprim) and dihydropteroate synthetase (sulfamethoxazole)

Question 50

Indications for TrimethoprimSulfamethoxazole Therapy

Answer 50

Question 51

Contraindications and Precautions of Trimethoprim-Sulfamethoxazole Therapy

Answer 51

Question 52

“Red man syndrome” and Drug-induced linear immunoglobulin A disease are possible cutaneous adverse reactions of what drug?

Answer 52

vancomycin

Question 53

**oxazolidinone** approved for the treatment of complicated SSTIs caused by MRSA, VRE, and vancomycin-resistant S. aureus

Answer 53

Linezolid and Tedizolid

Question 54

Oxazolidinones inhibit protein synthesis by binding to what portion of the 50S ribosomal subunit, a unique mechanism that minimizes cross-resistance to other antibiotics.

Answer 54

**23S portion** of the 50S ribosomal subunit,

Question 55

**streptogramin antibiotics** combined in a fixed ratio of 3:7

Answer 55

Quinupristin and dalfopristin

Question 56

Daptomycin, a member of the lipopeptide antibiotic class derived from the fermentation of Streptomyces roseosporus, exerts its activity via a multistep process involving the disruption of bacterial cell wall function What is the primary serious adverse event of this drug?

Answer 56

**myopathy**, which is usually transient and reversible, without progression to rhabdomyolysis

Question 58

mechanism of action of mupirocin

Answer 58

Reversibly binds to **isoleucyl-transfer RNA synthetase;** inhibits protein synthesis

Question 59