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MOD II Exam II > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What aspects of bacterial machinery can be inhibited by abx?

A 
Cell wall synthesis
Protein synthesis
DNA/RNA synthesis
Folate synthesis
Membrane integrity
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2
Q

Cell wall synthesis inhibitors

A

Beta-lactams (penicillin, cephalosporin, carbapenems, monobactams)

Glycopeptides and lipoglycopeptides

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3
Q

How do glycopeptides and lipoglycopeptides differ mechanistically from the beta lactams?

A

Beta lactams bind to and inhibit transpeptidase while glycopeptides and lipoglycopeptides bind to cell wall precursors and prevent cross linking/extension

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4
Q

Which abx relies on renal dipeptidase inhibitor celastatin?

A

Imipenem

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5
Q

What differentiates second generation cephalosporins from cephamycins?

A

The bacterial spectrum

Cephamycins are active against B.fragilis and some Serratia spp. and the purely second generation cephalosporins (cefaclor, cefprozil, and cefuroxime) are not

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6
Q

What is the general spectrum of coverage for the monobactam aztreonam

A

Gram-negative aerobes

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7
Q

What are the protein synthesis inhibitors that bind the 50s ribosomal subunit?

A

Oxazolidinones
Macrolides and ketolides
Streptogramins

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8
Q

What are the protein synthesis inhibitors that bind the 30s ribosomal subunit?

A

Tetracyclines
Aminoglycosides
Glycylcyclines

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9
Q

What is the difference in MOA between oxazolidinones and streptogramins?

A

Oxazolidinones bind to P site on ribosome and prevent initiation of protein synth

Streptogramins have 2 headed mechanism as they are given in combined ratio — quinupristin inhibits polypeptide elongation and induces early termination of protein synth; dalfopristin impedes polypeptide chain formation and induces conformational change in 50S ribosomal subunit that enhances quinupristin binding

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10
Q

Why are macrolides grouped with the ketolides? What distinguishes a macrolide from a ketolide?

A

Grouped together bc similar MOAs, chemical structure, and adverse effects

Their bacterial coverage differs; ketolides can be active in macrolide resistant strains

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11
Q

What antibiotic acts as a DNA/RNA synthesis inhibitor?

A

Fluoroquinolones

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12
Q

What proteins do fluoroquinolones inhibit?

A

Topoisomerase II (DNA gyrase) and topoisomerase IV

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13
Q

What are some side effects of fluoroquinolones?

A

Abdominal discomfort, nausea, vomiting, C.diff induced colitis, HA, dizziness

Achilles tendon rupture

QT prolongation (moxifloxacin)

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14
Q

What are the 2 folate synthesis inhibitors?

A

Sulfonamides

Benzylpyrimidines

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15
Q

What is the antibiotic that works as a membrane integrity inhibitor?

A

Polymyxins

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16
Q

Why are sulfonamides and benzylpyrimidines synergistic?

A

Trimethoprim and sulfamethoxazole inhibit subsequent steps in THF biosynthetic pathway

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17
Q

Are polymyxins active against gram positive bacteria? Why?

A

No, because they do not have an outer membrane

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18
Q

Major mechanisms of antibiotic synergism

A

Blockade of sequential steps in metabolic sequence (TMP/SMX)

Inhibition of enzymatic inactivation (beta-lactamase inhibitors)

Enhancement of antimicrobial agent uptake (penicillins and vancomycin can increase uptake of aminoglycosides)

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19
Q

Major mechanisms of antibiotic antagonism

A

Inhibition of cidal activity by static agents (tetracyclines and penicillins)

Induction of enzymatic inactivation (P.aeruginosa and some other bacteria possess inducible beta-lactamases; some beta lactam abx are potent inducers of beta-lactamase production — imipenem, cefoxitin, ampicillin)

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20
Q

Which of the following is a mechanism underlying the resistance of strains of S.pneumoniae to fluoroquinolones?

A. Reduced topoisomerase sensitivity to inhibitors
B. Increased synthesis of PABA
C. Formation of methyltransferases that change receptor structure
D. Structural changes in porins
E. Formation of drug-inactivating hydrolases

A

A. Reduced topoisomerase sensitivity to inhibitors

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21
Q

What is the most likely mechanism of resistance for MRSA to methicillin?

A. Methylation of the binding site
B. Active efflux of drug from bacteria
C. Beta-lactamase production
D. Phosphorylation of the drug by bacterial enzymes
E. Structural modifications of transpeptidase

A

E. Structural modifications of transpeptidase

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22
Q

37 y/o female presents to clinic with low grade fever and sore throat. PE reveals tonsillar exudate and gram stain reveals high number of bacteria. A dx is made and penicillin G is prescribed because the identified tonsillar exudate has been shown to be sensitive to penicillin G.

Which of the following bacteria is most likely to be causing this patient’s infection?

A. Klebsiella pneumoniae
B. Clostridium difficile
C. Staphylococcus aureus
D. Streptococcus pyogenes
E. Pseudomonas aeruginosa
A

D. Streptococcus pyogenes

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23
Q

67 y/o woman presents to ED with nausea, vomiting, fever, and altered consciousness. Her vitals are BP 90/50 mm Hg, pulse 115 bpm, respirations 20/min and temp 103.6 F. PE reveals pt in distress with nuchal rigidity. Empirical IV therapy is initiated with ampicillin, ceftriaxone, and vancomycin.

Which of the following best explains the common mechanism of action that all 3 of these drugs possess?

A. Inhibition of THF synthesis
B. Misreading of mRNA template code
C. Inhibition of peptidoglycan synthesis
D. Blockade of peptidyl-transfer RNA translocation
E. Enhancement of DNA gyrase activity
A

C. Inhibition of peptidoglycan synthesis

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24
Q

A 5 y/o boy presents with ear pain despite being tx with amoxicillin. Your pediatrician partner suggests changing the pt’s prescription to amoxicillin + potassium clavulanate.

Which of the following best explains the advantage of this proposed drug combo over amoxicillin monotherapy?

A. Extended antibacterial spectrum against P.aeruginosa
B. Inhibition of bacterial inactivation of amoxicillin
C. Inhibition of renal excretion of amoxicillin
D. Increased influx of amoxicillin into bacteria
E. Decreased amoxicillin hypersensitivity

A

B. Inhibition of bacterial inactivation of amoxicillin

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25
Q

Female presents with leg pain and blood cultures reveal MRSA. Treatment is initiated with antibiotic that binds to P site on 50S ribosomal subunit and prevents the formation of ribosomal n-formylmethionine tRNA complex.

Which of the following drugs was most likely given?

A. Linezolid
B. Tigecycline
C. Gentamicin
D. Imipenem
E. Tetracycline
A

A. Linezolid

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26
Q

70 y/o male presents with c/o HA, nausea, vomiting, vertigo, tinnitus, and progressive hearing loss. Medical hx reveals that pt had been receiving an antibiotic for 2 weeks to treat a UTI d/t serratia marcescens.

The drug used was most likely a member of which of the following abx classes?

A. Cephalosporins
B. Polymyxins
C. Tetracyclines
D. Aminoglycosides
E. Glycopeptides
A

D. Aminoglycosides

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27
Q

A 42 y/o female presents with c/o dysuria. Medical hx reveals recurrent UTIs and congenital long QT syndrome. Analysis of clean-catch midstream urine sample shows many gram-negative rods.

Which of the following abx would be contraindicated in this pt?

A. Moxifloxacin
B. Aztreonam
C. TMP/SMX
D. Ceftriaxone
E. Meropenem
A

A. Moxifloxacin

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28
Q

Which drug class does the following list belong to:

Penicillin G

A

Penicillin

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29
Q

Which drug class does the following list belong to:

Ampicillin
Amoxicillin

A

Aminopenicillins

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30
Q

Which drug class does the following list belong to:

Methicillin
Nafcillin
Oxacillin
Dicloxacillin

A

Penicillinase-resistant penicillins

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31
Q

Which drug class does the following list belong to:

Ticarcillin
Carbenicillin
Piperacillin
Mezlocillin

A

Anti-pseudomonal penicillins

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32
Q

Which drug class does the following list belong to:

Cefazolin
Cephalexin

A

First generation cephalosporins

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33
Q

Which drug class does the following list belong to:

Cefuroxime
Cefaclor
Cefprozil

A

Second generation cephalosporins

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34
Q

Which drug class does the following list belong to:

Cefotetan
Cefoxitin

A

Cephamycins

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35
Q

Which drug class does the following list belong to:

Cefotaxime
Cefixime
Cefdinir
Ceftibuten
Ceftazidime
Ceftriaxone
Cefpodoxime proxetil
Cefditoren pivoxil
A

Third generation cephalosporins

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36
Q

Which drug class does the following list belong to:

Cefepime

A

Fourth generation cephalosporin

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37
Q

Which drug class does the following list belong to:

Ceftaroline fasamil
Ceftolozane

A

Fifth generation cephalosporins

38
Q

Which drug class does the following list belong to:

Imipenem
Meropenem
Doripenem
Ertapenem

A

Carbapenems

39
Q

Which drug class does the following list belong to:

Aztreonam

A

Monobactam

40
Q

Which drug class does the following list belong to:

Vancomycin

A

Glycopeptides

41
Q

Which drug class does the following list belong to:

Telavancin
Dalbavancin
Oritavancin

A

Lipoglycopeptides

42
Q

Which drug class does the following list belong to:

Clavulanic acid
Sulbactam
Tazobactam

A

Beta-lactamase inhibitors

43
Q

Which drug class does the following list belong to:

Linozolid
Tedizolid

A

Oxazolidinones

44
Q

Which drug class does the following list belong to:

Erythromycin
Clarithromycin
Azithromycin
Fidaxomicin

A

Macrolides

45
Q

Which drug class does the following list belong to:

Telithromycin

A

Ketolides

46
Q

Which drug class does the following list belong to:

Quinupristin
Dalfopristin

A

Streptogramins

47
Q

Which drug class does the following list belong to:

Doxycycline
Tetracycline
Minocycline
Demeclocycline

A

Tetracyclines

48
Q

Which drug class does the following list belong to:

Tigecycline

A

Glycylcylines

49
Q

Which drug class does the following list belong to:

Streptomycin
Gentamycin
Tobramycin
Amikacin
Neomycin
Paromomycin
Kanamycin
Netilmicin
A

Aminoglycosides

50
Q

Which drug class does the following list belong to:

Moxifloxacin
Ciprofloxacin
Enoxacin
Ofloxacin
Pefloxacin
Gatifloxacin
Gemifloxacin
Levofloxacin
A

Fluoroquinolones

51
Q

Which drug class does the following list belong to:

Sulfamethoxazole

A

Sulfonamides

52
Q

Which drug class does the following list belong to:

Trimethoprim

A

Benzylpyrimidines

53
Q

Which drug class does the following list belong to:

Polymyxin B
Colistin

A

Polymyxins

54
Q

MOA of penicillins

A

Inhibit growth of bacteria by interfering with transpeptidation reaction - thus inhibiting bacterial cell wall synthesis

55
Q

___ = gateway for penicillin to access cell wall in gram- bacteria

A

Porins

56
Q

Penicillin G fights what bacteria?

A

Gram+ cocci = S.pneumo, S.pyogenes, S.viridans

Certain gram-negative cocci = N.meningiditis

Spirochetes like T.pallidum

C.perfringens

57
Q

Adverse effects of penicillin G

A

Anaphylaxis (d/t HSR to beta lactam ring)

Nausea, vomiting, diarrhea

58
Q

Bacteria killed by aminopenicillins

A

E.coli
Proteus
Salmonella
Shigella

With beta lactamase inhibitors, can fight H.influenzae, E.coli, Klebsiella spp., proteus spp., and B.fragilis

59
Q

What bacteria are penicillinase resistant penicillins effective against

A

S.aureus

S.epidermidis

60
Q

Major mechanism of abx resistance to anti-pseudomonal penicillins

A

Beta-lactamase production

61
Q

What bacteria are anti-pseudomonal penicillins effective against?

A 
P.aeruginosa
Klebsiella pneumoniae
E.coli
H.influenzae
B.fragilis
62
Q

T/F: cephalosporins have an almost identical MOA to penicillins

A

True

63
Q

Mechanisms of bacterial resistance to cephalosporins

A

Beta-lactamase production
Altering porins
Altering transpeptidase
Upregulation of efflux pumps

64
Q

First gen cephalosporins generally have better coverage against gram ____ organisms, while third generation have better coverage against gram ____ organisms

A

Positive; negative

[note that second gen fall somewhere in the middle with 50/50 +/- coverage]

65
Q

Most common side effect to cephalosporin use

A

HSR to beta lactam ring = maculopapular rash several days after therapy; sometimes accompanied by eosinophilia and fever

66
Q

Only 3rd gen cephalosporin effective against p.aeruginosa

A

Ceftazidime

67
Q

______ is an abx that may displace bilirubin d/t its high affinity for serum albumin. This can potentially lead to jaundice in neonates, thus, ____ is the preferred agent

A

Ceftriaxone; cefotaxime

68
Q

Due to its high affinity for Ca, ceftriaxone can lead to ____

A

Biliary pseudolithiasis (gallstones)

69
Q

Which generation cephalosporin fights p.aeruginosa as well as provides excellent coverage against enterobacter spp, but has POOR activity against B.fragilis?

A

Fourth gen cephalosporin (cefepime)

70
Q

Which 5th gen cephalosporin is active against MRSA since it has increased binding to transpeptidase?

A

Ceftaroline

[this drug also effective against pseudomonas spp. - hard to tx! — note this one has gram+ coverage]

71
Q

T/F: all carbapenems require combination with a renal dipeptidase inhibitor: celastatin

A

False; only imipenem requires this

72
Q

MOA of carbapenems

A

Inhibition of transpeptidase - inhibiting cell wall synth (same as cephalosporins and penicillin)

73
Q

T/F: like penicillin and cephalosporins, carbapenems have the issue of abx-resistance d/t degradation by beta-lactamases

A

False

74
Q

Mechanisms of abx resistance to carbapenems

A

Porin alteration

Upregulation of enzymes toxic to carbapenems

75
Q

Carbapenems as a class are good agents for targeting gram ___ bacteria

A

Negative

76
Q

Adverse rxns to carbapenems

A 
Reactions at infusion site
Skin rash
Diarrhea
Vomiting
Nausea
Renal failure
Seizures
77
Q

MOA of monobactams

A

Binds and inhibits gram-negative specific sub-type of transpeptidase —> cell wall loses its rigidity

78
Q

T/F: aztreonam has no activity against gram positives or anaerobes

A

True

79
Q

T/F: penicillin allergic pts are able to tolerate aztreonam

A

True

80
Q

Aztreonam should not be given to pts allergic to what drug?

A

Ceftazidime

81
Q

Adverse effects of aztreonam

A

Hepatotoxicity

Skin rash

82
Q

MOA of glycopeptides

A

Bind D-alanyl-D-alanine terminus of cell wall precursor units with very high affinity —> prevents peptidoglycan synth

83
Q

Primary glycopeptide resistant strain of enterococci

A

E.faecium

84
Q

How must vancomycin be administered?

A

IV

85
Q

Vancomycin is effective against what?

A

Many gram+ bacteria

[Almost all gram negative bacilli and mycobacteria are RESISTANT to vancomycin]

86
Q

Adverse effects of vancomycin

A

Hypotension
Tachycardia
Flushing (“red man syndrome”)

Nephrotoxicity

87
Q

MOA of oxazolidinones

A

Bind P site on 50S ribosomal subunit, preventing initiation of protein synth by preventing formation of n-fMet tRNA complex

Primarily bacteriostatic, but bactericidal against streptococci!

88
Q

Mechanisms of resistance to Oxazolidinones

A

Point mutations on 23S rRNA that makes up Oxa. binding site on 50S subunit

89
Q

Oxazolidinones are acitve against a large majority of what type of bacteria

A

Gram+

[they have poor coverage of gram-neg]

90
Q

Adverse effects of oxazolidinones

A

Myelosuppression, thrombocytopenia, lactic acidosis, optic neuritis, peripheral neuropathy (mitochondrial toxicity), drug-drug interactions (MAOs, SSRIs)

91
Q

MOA of macrolides and ketolides

A

Bind reversibly to 50S subunit of bacterial ribosome, preventing translocation of tRNA from A site to P site, thus halting protein synth

They can also elicit conformational change in bacterial ribosome which can result in indirect inhibition of transpeptidation

Lastly, they can inhibit the formation of the 50S subunit

Bacteriostatic!

92
Q

4 main mechanisms of resistance to macrolides and ketolides

A

Drug efflux

Production of methylase

Degradation

Mutations in 50S ribosomal subunit

MOD II Exam II (7 decks)

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