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Antibiotics Flashcards

1
Q

Sulfonamides: spectrum and static/cidal?

A

broad, static

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2
Q

what general mechanism do sulfonamide inhibit?

A

synthesis of nucleotides - prevention of transcription and DNA replication

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3
Q

what is the exact mechanism of sulfonamides?

A

sulfonamides inhibit dihydropteroate synthetase by acting as a competitive inhibitor against PABA - they therefore inhibit folic acid synthesis

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4
Q

what drug is often used in conjunction with sulfonamides?

A

trimethoprim

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5
Q

what is the mechanism for trimethoprim?

A

it is used in conjunction with sulfonamides to block the folic acid synthesis pathway - it inhibits dihydrofolate reductase by competitively inhibiting DHFA

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6
Q

what is the selective toxicity of sulfonamides?

A

humans get folic acid from diet - we dont make it

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7
Q

what is the combined use of sulfonamide and trimethoprim an example of?

A

synergism

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8
Q

what is p-aminosalicylic acid (PAS)

A

it works similar to sulfonamides but is effective against mycobacterium tuberculosis while sulfonamides are not

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9
Q

what is the spectrum and cidal/static action of rifampin and rifabutin?

A

narrow: G+ (staph and strep), Neisseria, and Mycobacteria

cidal

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10
Q

spec/stat/cidal for quinolones?

A

cidal for narrow spectrum of G- (E. coli, Proteus, Klebsiella, Enterobactor)
often used for UTIs

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11
Q

what is the mechanism of quinolones?

A

block bacterial gyrase and topoisomerase

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12
Q

what are “floxin’s” used for? (spectrum and a specific organism)

A

broad spectrum

active against pseudomonas

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13
Q

what does metronidazole affect?

A

nucleic acid synthesis - DNA breaks and secondary mutations

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14
Q

what is the spect for metronidazole?

A

narrow for anaerobic infections

also for protozoal infections due to Entamoeba histolytica and Giardia lamblia

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15
Q

what is the selevtive toxicity for metridonazole

A

it is a prodrug that is only metabolized by bacterial nitroreductases

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16
Q

what is the spect for polymyxins?

A

narrow - pseudomonas

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17
Q

what is an example of a polymyxin?

A

colistin

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18
Q

mechanism of polymyxin?

A

has hydrophilic head and tail - tail gets inserted into membrane and head binds to phosphatidylethanolamine )PE) and LPS

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19
Q

what is the enzyme that makes special amino acids for peptidoglycans?

A

racemase

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20
Q

what is the antibiotic that targets racemase?

A

cycloserine

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21
Q

what antibiotic prevents transglycosylation?

A

vancomycin - it binds the D-ala-D-ala and sterically hindering the assembly of disaccharide units

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22
Q

what species can you use vancomycin for?

A

MRSA and enterococcus (G+)

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23
Q

what is the conferred resistance that bacteria have developed to vancomycin?

A

use D-ser or D-lac instead of D-ala

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24
Q

what type of cross-linking is present in Gram - bacteria?

A

adjacent D-ala’s

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25
Q

what type of cross-linking is present in Gram + bacteria?

A

adjacent D-ala’s
also pentaglycine bridges

*this makes the cell wall thicker

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26
Q

what enzymes perform transpeptidation?

A

transpeptidases and carboxypeptidases - they recognize D-ala-D-ala and catalyze the cross links

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27
Q

what enzymes work against transpeptidation?

A

beta-lactmas like penicillin which look a lot like D-ala so they sequester transpeptidases and carboxypeptidases

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28
Q

what are some examples of beta-lactams?

A

monobactam, penicillin, cephalosporin, cephamycin, carbapenem

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29
Q

what is the name for the class of molecules that includes transpeptidases and carboxypeptidases?

A

penicillin-binding proteins

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30
Q

what are the two ways bacteria inhibit penicillins/beta-lactams?

A

make substance that inactivates it; alter the target of the beta-lactam

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31
Q

what is an example of a bacterial resistance enzyme against beta-lactams?

A

beta-lactamase (aka penicillinase) - it breaks down the beta-lactam ring of penicillin

also have cephalosporinases

32
Q

what are the first generation penicillins?

A

penicillin G, V

best for GM+

33
Q

what are the 2nd and 3rd generation penicillins

A

ampicillin (GM- too)
amoxacillin (GM+ and -)
methicillin, oxacillin, nafcillin (beta-lactamase resistance)
carbenicillin, ticarcillin, piperacillin ( also works for pseudomonas)

34
Q

how does methicillin resistance work?

A

change the target of the antiobiotic method - so you change the transpeptidase so that methicillin cannot bind to it - it is called penicillin binding protein 2

35
Q

how can you use beta-lactamase inhibitors?

A

use them in conjuction with a penicillin so that the inhibitor can work and then the the anitbiotic can work

36
Q

what is an example of the conjuction of a beta-lactamase inhibitor and a penicillin?

A

augmentin

combo of amoxicillin and clavulanic acid

37
Q

what is the spect/cidial/static foe daptomycin?

A

narrow for GM+ and cidal

38
Q

what is chemical composition of daptomycin?

A

it is a cyclic amino acid structureq

39
Q

what is the mechanism of daptomycin action?

A

it aggregates on the cell membrane of the bacteria and the lipid tail inserts into the cell membrane, making a pore that causes loss of membrane potential - cell death

40
Q

what is daptomycin a good alternative for?

A

vancomycin use against MRSA

41
Q

list the drugs that inhibit cell wall synthesis

A

penicillin, cephalosporing, carbepenums, monobactams (transpeptidation)
bacitracin (inhibits export of PG components)
vancomycin (inhibits transglycosylation)

42
Q

list the drugs that disrupt the cell membrane

A

polymyxins, daptomycin

43
Q

what are the antibiotics that target amino acid activation in bacterial protein synth?

A

none!

44
Q

what are the antibiotics that target formation of the initiation complexes of ribosomes

A

linezolid

45
Q

what does linezolid do?

A

it inihibits the formation of the 70S initiation complex (tRNA, mRNA, 70S complex) by binding peptidyltransferase center

46
Q

what is the spectrum/static/cidal for linezolid?

A

static for staph and enterococci
cidal for strep
ONLY approved for G+
can be lethal when given for G-

47
Q

what do aminoglycosides inhibit?

A

targets specific proteins in 30S subunit, blocking codon/anticodon interaction

48
Q

what are some aminoglycosides?

A

streptomycin, kanamycin, paramomycin, amikacin, tobramycin, neomycin, gentamycin

49
Q

what is the spectrum/static/cidal for aminoglycosides?

A

broad (G+,-)

cidal

50
Q

what is one important thing about aminoglycosides?

A

it functions against tuberculosis

51
Q

what are the three mechanisms of action of streptomycin?

A

misreading: incorrect aa inserted
cyclic polysomal blockade: 70S complex forms but falls apart due to instability
faulty outer membrane proteins: due to misreading, faulty membrane proteins disrupt the membrane

52
Q

what are some bad side effects of streptomycin?

A

ototoxicity and nephrotoxicity

53
Q

what can make aminoglycosides less effective?

A

anaerobisis, low pH, ions

54
Q

what is spectinomycin?

A

an aminocyclitol antibiotic that affects codon/anticodon reaction

55
Q

is spectinomycin static or cidal?

A

static

56
Q

what is the mechanism of action of spectomycin?

A

it causes unstable formation of 70S initiation complexes

57
Q

what do we use spectomycin for?

A

gonorrhea caused by beta-lactamase producing gonococci

58
Q

spectrum/static/cidal for tetracycline?

A

broad, static

59
Q

what is the mechanism of action for tetracycline?

A

interrupts codon/anticodin interactions -it binds to 30S ribosomal subunit preventing binding of first tRNA

60
Q

what do we use tetracycline for?

A

chlamydia, mycoplasma, rickettisa and intercellular pathogens

61
Q

spect/cidal/static for chloramphenicol?

A

broad spectrum, static

62
Q

what is the mechanism for chloramphenicol?

A

it blocks peptiyl transfer by binding to the 50S subunit and altering the tRNA structure

63
Q

spect/cidal for lincomycin and clindamycin?

A

static

narrow - good for G+ bacterial infections, staph, and anaerobic G-

64
Q

what is the mechanism for lincomycin and clindamycin?

A

similar to cloramphenicol - binds to 50S subunit and alters tRNA, preventing peptidyl transfer

65
Q

spect/cidal/static for macrolides?

A

medium spectrum, static
good against intracellular pathogens - mycoplasma, legionella, chlamydia, campylobacter and G+ in pts allergic to penicillin

66
Q

what are some examples of macrolides?

A

azithromycin and clarithromycin

67
Q

mechanism for macrolides?

A

block translocation

68
Q

spect/cidal/static for ketolides?

A

cidal or static depending on bacterium and strength of interaction

69
Q

what is the mechanism of ketolides?

A

works by binding within the exit tunnel of 50S unit, blocking exit of nascent polypeptides; it strongly binds to two domains of RNA of ribosome

70
Q

what is an example of a ketolide?

A

telothromycin

71
Q

what is streptogramin?

A

a cyclic peptide antibody that is produced by subspecies of streptomyces

72
Q

what is the mechanism of streptogramin?

A

blocks translocation

73
Q

what are some examples of streptgramins?

A

dalfopristin, quinupristin, and synercid (quinupristin &dalfopristin together - they are cidal together, static alone)

74
Q

what organisms can you use streptogramins against?

A

staph, strep, enterococcus, but primarily for treating vancomycin resistant enterococcus

75
Q

what is the mechanism for rifampin/rifabutin

A

binds to beta-subunit of RNA polymerase, inhibiting transcriptional initiation

Musculoskeletal (21 decks)

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