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Common Mechanisms Block 2 > Pharmacology -- Antimicrobial Agents > Flashcards

Pharmacology -- Antimicrobial Agents Flashcards

1
Q

What are the four major mechanisms of antibacterial resistance?

A

Alterations in receptor target, Decreased entry or efflux of drug, alterations in metabolic pathways, or drug inactivation

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2
Q

Penicillins are bactericidal or bacteriostatic? Bind ___ to crosslink NAM/NAG

A

Bactericidal; Transpeptidase

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3
Q

Penicillin-Binding Proteins are ____, _____, and ____

A

Transpeptidase, autolysins, and carboxypeptidases + endopeptidases

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4
Q

Resistance to Penicillins occurs in what 4 ways?

A

Modification of PBPs, Active pumping/efflux, cleavage of B-lactam by B-lactamases, and altered porins (prevent drugs from reaching target)

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5
Q

Why would the action of penicillin be antagonized if given alongside a bacteriostatic drug like tetracycline?

A

Need bacteria to actively grow in order to effectively inhibit cell wall synthesis

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6
Q

If penicillins are given in combo with an oral contraceptive, what will occur?

A

Less efficacy of oral contraceptive since antibiotics disrupt normal (gut) flora

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7
Q

What are the four classes of penicillins?

A

Natural penicillins, aminopenicillins, penicillinase-resistant penicillins, and antipseudomonal penicillins

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8
Q

What are the two natural penicillins? They are used to treat gram _____ (positive or negative).

A

Penicillin G, Penicillin V; positive

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9
Q

What are the two possible routes of administration of penicillin G? Why?

A

Intravenous or intramuscular; destroyed in acidic environments like GI tract

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10
Q

What is the route of administration of penicillin V? Timing?

A

Oral; 1 hour before meal or 2-3 hour after

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11
Q

What are the two aminopenicillins? They are primarily used to treat gram _____ (positive or negative)

A

Ampicillin, amoxicillin; negative

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12
Q

Aminopenicillins are administered ______ (enterally, parenterally, or both).

A

Both

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13
Q

What are the four penicillinase-resistant penicillins? They tend to be used to treat gram _____ (positive or negative).

A

Dicloxacillin, methicillin, oxacillin, and nafcillin; positive

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14
Q

Of the four penicillinase-resistant penicillins, which ones are given parenterally?

A

Methicillin, oxacillin, and nafcillin

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15
Q

Of the four penicillinase-resistant penicillins, which is given orally?

A

Dicloxacillin

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16
Q

What are the four antipseudomonal penicillins? They tend to be used to treat gram _____ (positive or negative).

A

Carbenicillin, Ticarcillin, Mezlocillin, and Piperacillin; negative

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17
Q

Antipseudomonal penicillins typically are administered _____ (enterally, parenterally, or both).

A

Parenterally

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18
Q

Which of the antipseudomonal penicillins can be administered orally? Its enteral utility is limited to what type of infections (location)?

A

Carbenicillin; Urinary tract/prostatic infections

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19
Q

What are the three B-lactamase inhibitors? Are they irreversible or reversible? What is their clinical use?

A

Clavulanic acid, sublactam, tazobactam; irreversible; not antimicrobial but provide expanded coverage to B-lactamase-producing organisms when combined w/ penicillin

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20
Q

Cephalosporins structurally resemble _____. What two ways do they differ from this other class of drugs?

A

Penicillins; differ from natural penicillins in their stability under pH change and ability to be taken with or without food

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21
Q

What are the adverse effects of cephalosporins?

A

Penicillin-allergic patients, GI irritation, Parenteral irritation, Renal toxicity, Disulfiram-like Reactions and hypothrombinemia, seizures, secondary infections

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22
Q

What are the carbapenems? Are they bactericidal or bacteriostatic? By what mechanism? Resistant or susceptible to B-lactamases?

A

Imipenem/cilastatin, doripenem, ertapenem, and meropenem; bactericidal; inhibit cell wall synth.; Resistant

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23
Q

What two drugs can interfere with cell wall synthesis by blocking polymerization and cross-linking of peptidoglycan by binding to D-Ala-D-Ala portion of cell walls? Which one also has other mechanisms involving disruption of membrane potential and changes in cell permeability?

A

Telavancin, Vancomycin; Telavancin

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24
Q

Which antimicrobial inhibits cell wall synthesis in both gram positive and gram negative organisms? Usually reserved for treating?

A

Cycloserine; M. tuberculosis when infection resistant to first-line anti-tubercular drugs

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25
Q

Which antimicrobial acts as a cationic detergent that disrupts lipoproteins in bacterial cell wall? It is _____ (bactericidal or bacteriostatic) against nearly all Gram _____ (positive or negative, cocci or bacilli) with exception of Proteus.

A

Polymyxin B; Bactericidal; Gram negative bacilli

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26
Q

What are the 7 aminoglycosides?

A

Amikacin, gentamicin, kanamycin, netilmycin, streptomycin, tobramycin, and neomycin

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27
Q

Aminoglycosides bind to ____ of the ribosome interfere with protein synthesis in what 3 ways? Reliably used only in treating gram ____ (positive or negative) infections.

A

Formation of initiation complex, misread mRNA/miscoding of AA, and cause ribosome to separate from mRNA; negative

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28
Q

Aminoglycosides are usually given _____ (enterally, parenterally, or both). Their toxic effects are _____ and _____. They exhibit what is known as the _____ effect, where they continue to have effects after the antibiotic has been eliminated.

A

Parenterally; Nephrotoxicity, ototoxicity; Postantibiotic

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29
Q

_____ (anaerobes or aerobes) acquire resistance to aminoglycosides by alteration in receptor proteins on ribosomes. Others can enzymatically or posttranslationally alter through _____, _____, or _____.

A

anaerobe; phosphorylation, acetylation, or adenylation

30
Q

What are the six tetracyclines?

A

Tetracycline, minocycline, doxycycline, demeclocycline, oxytetracycline, and tigecycline

31
Q

Tetracyclines inhibit protein synthesis through _____ (reversible or irreversible) binding to ____ (30S or 50S) ribosomal subunit, thus making them _____ (bactericidal or bacteriostatic).

A

Reversible; 30S; Bacteriostatic

32
Q

Glycyclines are antibiotics derived from tetracycline designed to overcome what two common mechanisms of resistance?

A

Resistance mediated by efflux pumps and ribosomal protection

33
Q

Tigecycline is most closely related to what other tetracycline?

A

Minocycline

34
Q

Tetracyclines penetrate gram negative bacteria by _____ (passive diffusion or active transport), and they penetrate gram positive bacteria by _____ (passive diffusion or active transport).

A

Passive diffusion; active transport

35
Q

Gastric absorption of tetracyclines is inhibited by chelation to ____ or ____. Tetracyclines are best administered on a _____ (full or empty) stomach.

A

divalent cations, bile acid resins; empty

36
Q

Which tetracycline is the safest option for patients with renal dysfunction? Why?

A

Doxycycline; because it is metabolized hepatically and excreted via the feces

37
Q

Gram positive bacteria acquire resistance to tetracyclines via _____, while gram negative organisms acquire resistance to tetracyclines via _____. Which tetracycline is not affected by resistance mechanisms?

A

Efflux Pumps; Outer membrane proteins; Tigecyline

38
Q

Chloramphenicol is a _____ (bactericidal or bacteriostatic) agent. It binds to the ____ (30S or 50S) ribosomal subunit and blocks linkage of incoming AA to growing peptide chain by interfering with _____.

A

Bacteriostatic; 50S; Peptidyl transferase

39
Q

Chloramphenicol is metabolized via _____. Accumulation due to inefficiency in this process in both adults and children can result in what is known as _____

A

Glucuronidation; Gray Baby/Gray adult

40
Q

The common lincosamide drug is known as _____, and it acts to interrupt protein synthesis by binding to the ___ (30S or 50S) ribosomal subunit and preventing the _____.

A

Clindamycin; 50S; translocation of incoming AAs from A site to P site

41
Q

What are the 6 macrolides we need to know?

A

Erythromycin base, erythromycin estolate, erythromycin stearate, erythromycin ethylsuccinate, clarithromycin, and azithromycin

42
Q

Macrolides act to inhibit protein synthesis by binding the same site on prokaryotic ____ (30S or 50S) ribosomal subunits as _____ and ____ bind, thus preventing _____.

A

50S; clindamycin, chloramphenicol; translocation of AA from A to P site

43
Q

How might macrolides develop cross-resistance?

A

Share same binding site as clindamycin and chloramphenicol and may interfere with one another

44
Q

What is unique about the toxic effects of macrolides on bacteria?

A

Can be both bacteriostatic or bactericidal depending on drug concentration

45
Q

By what 3 mechanisms does resistance to macrolides occur?

A

Permeability alteration, methylation of bacterial 50S ribosomal subunit, development of mechanisms to enzymatically destroy the drug

46
Q

Which macrolides are most associated with GI distress? Which one may cause cholestatic hepatitis? What are two other important adverse effects?

A

Erythromycins; Estolate salt; Inhibition of CYP3A4; QT prolongation

47
Q

What other macrolide other than the erythromycins can cause QT prolongation?

A

Clarithromycin

48
Q

Which macrolide does not cause QT prolongation or inhibition of CYP3A4

A

Azithromycin

49
Q

The ketolide drug we need to know is ____. It acts to inhibit the ___ (30S or 50S) ribosomal subunit. What is unique about its action? Is it a good or poor substrate for efflux pumps?

A

Telithromycin; 50S; it binds to two separate domains; Poor

50
Q

Which inhibitor of antimicrobial protein synthesis is available as a topical ointment and is structurally considered to be a pleuromutilin antibiotic? It inhibits protein synthesis by interfering with ____ by binding to a site on the ___ (30S or 50S) ribosomal subunit. This binding allows what three results?

A

Retapamulin; Peptidyl transferase; 50S; Prevention of formation of active subunit, inhibition of peptidyl transferase, and blockage of P-site interactions

51
Q

Which antimicrobial is available as a topical cream and ointment, results in no cross-resistance, and inhibits the tRNA that transports isoleucine?

A

Mupirocin

52
Q

Which antimicrobial protein synthesis inhibitor interferes with synthesis by binding to a unique RNA site on the 50S subunit, thus preventing formation of functional 70S?

A

Linezolid

53
Q

Streptogramins are a combination of what two compounds? They ____ (reversibly or irreversibly) block ribosomes and inhibit ____ (early or late) phases of protein synthesis.

A

Quinupristin, dalfopristin; Irreversibly; late

54
Q

What are the 6 sulfonamides we need to know?

A

Sulfadiazine, silver sulfadiazine, sulfisoxazole, sulfamethoxazole, sulfacetamide, and sulfasalazine

55
Q

Sulfonamides act to compete with _____ at the first step of the folic acid synthesis pathway and inhibit _____.

A

Para-aminobenzoic acid (PABA); Dihydropteroate Synthetase

56
Q

What is important about the pharmacokinetics of sulfonamides? Metabolized hepatically by _____, _____, and/or _____. Genetically slow metabolizers are at increased risk for what? Which biotransformation is likely responsible for many of the adverse effects. After biotransformation, how are the sulfonamides excreted?

A

Highly bound protein that can have DDI with warfarin, NSAIDs, and sulfonylureas; acetylation, oxidation, and/or glucuronidation; acetylators at inc. risk for hypersensitivity reaction; oxidation; Renally

57
Q

What drug inhibits folic acid synthesis by inhibiting dihydrofolate reductase? What mechanisms do bacteria use to develop resistance to this drug?

A

Trimethoprim; Reduced uptake, alteration or mutation of dihydrofolate reductase, or overproduction of dihydrofolate reductase

58
Q

What are the 8 fluoroquinolones that we need to know?

A

Besifloxacin, norfloxacin, gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, norfloxacin, and ofloxacin

59
Q

Fluorquinolones are _____ (bactericidal or bacteriostatic) and interfere with ____ by inhibiting one of two enzymes: ____ or ____. Which fluoroquinolone is effective at inhibiting both?

A

Bactericidal; DNA synthesis; DNA gyrase; Topoisomerase IV; Gemifloxacin

60
Q

____ or ____ may impair absorption of fluoroquinolones. ____ also interferes with absorption. Distributes to _____.

A

Food, cations; Sucralfate; Nearly all body compartments

61
Q

The lipopeptide drug we need to know is ____. Acts by binding to bacterial membrane and causing what? Does it develop cross-resistance? It is primarily eliminated ____.

A

Daptomycin; rapid depolarization; No; unchanged in urine

62
Q

Metronidazole is selectively absorbed by what microbes: ____ and ____? It is _____ (enzymatically or nonenzymatically) reduced by reacting with _____, thus causing what? Does it distribute to CNS?

A

anaeobic bacteria, sensitive protozoa; nonenzymatically; reduced ferredoxing; production of metabolites toxic to anaerobic cells; Yes

63
Q

Which antimicrobial interferes with pyruvate/ferredoxin oxidoreductase enzyme-dependent electron transfer essential for anaerobic metabolism?

A

Nitazoxanide

64
Q

Which antimicrobial is believed to cause cytotoxicity by damaging DNA and further inhibiting synthesis?

A

Tinidazole

65
Q

Which antimicrobial is an inhibitor of RNA synthesis by binding to bacterial DNA-dependent RNA polymerase? What drug is it related to? How does it differ from that drug?

A

Rifaximin; Rifampin; Not absorbed from GI/excreted unchanged from feces and does not interfere with CYP450

66
Q

Mycobacteria are ____ (morphology), ____ (gram positive or negative), ____ (anaerobic or aerobic) bacteria.

A

Rodlike; Gram positive; aerobic

67
Q

Why are mycobacterial infections difficult to treat (5 reasons)?

A

Grow slowly, can lie dormant, thick/impermeable cell walls, can reside in host cells, and develop resistance quickly

68
Q

Which anti-mycobacterial inhibits synthesis of mycolic acids?

A

Isoniazid

69
Q

Isoniazid distributes to ____ (location), ____ (excluding or including CNS). It is metabolized via ____.

A

Total body water; including; acetylation

70
Q

Which anti-mycobacterial agent inhibits bacterial RNA polymerase and prevents transcription by suppressing initiation of RNA chain formation? What is unique about its pharmacokinetics?

A

Rifampin; potent inducer of drug metabolism/DDI is a major concern

71
Q

Which anti-mycobacterial agent inhibits RNA synthesis and acts to decrease replication of tubercle bacilli? (Vague, I know)

A

Ethambutol

72
Q

Which anti-mycobacterial agent acts by binding to mycobacterial DNA and inhibiting RNA polymerase reactions? Is it bactericidal or bacteriostatic?

A

Clofazimine; bactericidal

Common Mechanisms Block 2 (5 decks)

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