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ID > Penicillins & Cephalosporins > Flashcards

Penicillins & Cephalosporins Flashcards

1
Q

beta lactams target ______ by interfering with ______

A

cell wall synthesis, transpeptidase

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2
Q

bacterial cell wall is a cross-linked polymer called _______ which allows a bacteria to maintain its shape despite the internal pressure caused by ______

A

peptidoglycan, osmotic pressure differences

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3
Q

if the peptidoglycan fails to _____, the cell wall will lose its strength which results in cell lysis

A

crosslink

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4
Q

the cross linking reaction is catalyzed by a class of transpeptidases known as ________

A

penicillin binding proteins (PBPs)

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5
Q

a critical part of the cross linking process is the recognition of the ________ sequence of the NAMA peptide side chain by the PBP

A

D-Ala-D-Ala

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6
Q

beta lactams mimic the structure of the _______ link and bind to the active site of _____, disrupting the cross-linking process

A

D-Ala-D-Ala, PBPs

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7
Q

the ____ of the beta lactam ring is unusually reactive due to ring strain

A

amide

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8
Q

beta lactams acylate the _____ group on the serine residue of PBP active site in an irreversible manner

A

hydroxyl

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9
Q

what is the “secondary” mechanism of beta lactams that cannot occur without the primary mechanism

A

the bacteria detect a “defect” in its cell wall so it produces more peptidoglycan. in doing so, it produces autolysin, which is an enzyme produced by the bacteria to remove damaged cell wall for repair (slices off its own cell wall)

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10
Q

what are 3 mechanisms of bacterial resistance

A

efflux pumps, beta lactamases, mutation at genes that control PBP production

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11
Q

how do beta lactamases render beta lactams useless

A

they hydrolyze the amide bond of the beta lactam ring

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12
Q

beta lactams can easily penetrate _____ bacteria

A

gram positive

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13
Q

the outer membrane of ____ bacteria makes diffusion of beta lactams to the site of activity challenging

A

gram negative

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14
Q

any bacteria which lack ____ will not be affected by beta lactams

A

peptidoglycan

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15
Q

why are beta lactams relatively non toxic

A

they target PBPs exclusively, human cell membranes don’t have PBPs

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16
Q

penicillin __ is not orally active due to gut acidity

A

G

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17
Q

penicillin __ is orally viable and acid stable because of an added oxygen

A

VK

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18
Q

caution with high potassium/ESRD for which natural penicillin

A

VK

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19
Q

what was oral penicillin historically used for

A

dental prophylaxis in patients w/ prosthetic heart valves

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20
Q

when is oral penicillin actually used now

A

dental infections (soft tissue impacted molar), IM for syphilis, IV for susceptible severe streptococcal infections

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21
Q

______ are enzymes that hydrolyze the beta lactam ring, deactivating the drug

A

beta lactamases

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22
Q

beta lactamases can be present in both gram positive and negative bacteria, but they are a significant focal point in _____

A

gram negative, particularly those causing nosocomial infections

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23
Q

________ penicillins have a notable large R group which can block the beta-lactamases which hydrolyze the beta lactam ring

A

anti-staphylococcal

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24
Q

what are the oral anti-staphylococcal penicillins

A

cloxacillin, dicloxacillin

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25
Q

what are the IV anti-staphylococcal penicillins

A

oxacillin, nafcillin

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26
Q

what is the downside to anti-staphylococcal penicillins

A

due to the bulky side group, they have difficulty penetrating the cell membrane and are less effective against gram negative bacteria (no clinically relevant activity)

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27
Q

staphylococcus produces _____

A

penicillinase (beta lactamase)

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28
Q

Pen VK/G activity against staphylococci

A

extremely limited

29
Q

Pen VK/G activity against streptococci

A

good activity against some: pyogenes is always susceptible, pneumoniae is mostly susceptible

30
Q

anti-staphylococcal penicillin activity against staphylococcus

A

excellent activity against MSSA, no activity against MRSA

31
Q

anti-staphylococcal penicillin activity against streptococci

A

little to no activity

32
Q

_________ have more hydrophilic groups, allowing the drug to penetrate into gram negative bacteria via the outer membrane porins

A

aminopenicillins

33
Q

downside to aminopenicillins

A

without the bulky R group of the anti-staphylococcal PCNs, they are once again susceptible to attack by beta lactamases

34
Q

the hydrophilic groups of aminopenicillins also allow for greater absorption in the ____

A

GI tract

35
Q

aminopenicillins are the drugs of choice for _____

A

enterococcus and listeria

36
Q

acronym for aminopenicillin activity

A

HELPS: hemophilus, enterococcus, listeria, proteus, salmonella/shigella

37
Q

PO frequency of administration for ampicillin

A

4x/day

38
Q

PO frequency of administration for amoxicillin

A

3x/day

39
Q

which aminopenicillin is more bioavailable

A

amoxicillin, less frequency of diarrhea too

40
Q

ampicillin with regards to food?

A

should be administered PO on an empty stomach, food decreases absorption and peak plasma concentration

41
Q

amoxicillin with regards to food?

A

may be taken without regards to meal

42
Q

what are the IV beta lactamase inhibitors

A

sulbactam, tazobactam

43
Q

what is the PO beta lactamase inhibitor

A

clavulanic acid

44
Q

what are the first generation cephalosporins

A

cefazolin, cephalothin, cephalexin, cefadroxil

45
Q

which first generation cephalosporins are PO

A

cephalexin, cefadroxil

46
Q

what is the spectrum of activity for first generation cephalosporins

A

excellent against MSSA and streptococci, no activity against enterococcus, limited activity against gram negative, no activity against gram negative obligate anaerobes in the gut

47
Q

first generation cephalosporins are excreted by the _____ unmetabolized

A

kidney

48
Q

dose adjustments for first generation cephalosporins are made for patients with _____

A

poor kidney function

49
Q

what are the second generation cephalosporins

A

cefaclor, cefuroxime, cefprozil

50
Q

what second generation cephalosporins are PO

A

cefaclor, cefuroxime, cefprozil

51
Q

what second generation cephalosporins are IV

A

cefuroxime

52
Q

spectrum of activity for second generation cephalosporins

A

slightly less potent against gram positive, increased activity against gram negatives

53
Q

given the spectrum of first generation cephalosporins, what are they good for

A

skin and skin structure infections, clean surgical procedures

54
Q

given the spectrum of second generation cephalosporins, what are they good for

A

URTIs (bacterial sinusitis, otitis media), UTIs

55
Q

the PO form of cefuroxime is a ____ that increases absorption by increasing lipophilicity

A

prodrug

56
Q

______ possess a methoxy group at the 7-alpha position of the cephem ring instead of a carboxylic acid

A

cephamycins

57
Q

what are the cephamycins

A

cefoxitin and cefotetan

58
Q

cefoxitin and cefotetan possess ______ activity whereas other 2nd generation cephalosporins do not

A

gram-negative obligate anaerobic

59
Q

_______ contains an N-methylthiotetrazole side chain (NMTT or 1-MTT) that can lead to inhibition of vitamin K epoxide reductase and increase prothrombin times and risk for bleed

A

cefotetan

60
Q

if the cephamycins have anaerobic activity why are they not used in the setting of active infection where obligate anaerobes are present

A

due to resistance. so they are used for peri-operative prophylaxis

61
Q

what are the third generation cephalosporins

A

cefotaxime, ceftriaxone, ceftazidime, cefpodoxime, cefixime, ceftibuten, cefdinir, cefditoren

62
Q

spectrum for third generation cephalosporins

A

broad spectrum gram negative

63
Q

the third generation cephalosporins are mostly excreted by the kidney except for ______ which undergoes enterohepatic recycling

A

ceftriaxone

64
Q

therapeutic uses for third generation cephalosporins in the community

A

otitis media (recurrent/frequent), URTI

65
Q

cefpodoxime PO form is a ______ that increases absorption by increasing lipophilicity

A

prodrug

66
Q

bioavailability of cefpodoxime proxetil is ____

A

50%

67
Q

what is different about ceftazidime

A

gram negative coverage includes pseudomonas aeruginosa

68
Q

what is pseudomonas aeruginosa

A

nosocomial pathogen typically causing infections in hospitalized patients

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