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Respiratory Medicine-Unit 1 > Beta lactams and cell wall synthesis inhibitors (Fitz) > Flashcards

Beta lactams and cell wall synthesis inhibitors (Fitz) Flashcards

1
Q

Because B-lactams resemble ___, they inhibit cross-linking enzyme(s)/Transpeptidases

A

D-ala-D-ala

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2
Q

Which enzyme is a target of Pencillins (and other B lactams)?

A

transpeptidase

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3
Q

These penicillins are narrow spectrum but potent and effective drugs against sensitive strains of gram + cocci, certain gram - cocci, certain gram + anaerobic species, spirochetes

A

Natural penicillins –> G and V

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4
Q

What gram + cocci and diseases are clinically indicated for use of natural penicillins?

A

S. pneumo –> pneuomococcal pneumonia (resistant)
S. pypgenes –> pharyngitis, scarlet fever
S viridans group –> endocarditis

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5
Q

What are routes of Penicillin G? Penicillin V?

A

G –> IV, IM, PO (low bioavailability); distributed into CNS with inflamed meninges

V–> PO, stable at gastric, acidic pH and has good oral bioavailability

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6
Q

What is a complication of natural penicillins?

A

Hypersensitivity –> includes life-threatening anaphylaxis

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7
Q

This enzyme produced by bacterial pathogens renders them penicillin resistant

A

B lactamase –> cleaves B lactam rings, inactivating penicillin G and conferring drug resistance

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8
Q

B lactamase enzymes efficiently degrades these natural penicillins:

A

Penicillin G and V

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9
Q

B lactamase enzymes efficiently degrades these extended spectrum abx:

A

ampicillin, amoxicillin

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10
Q

B lactamase enzymes efficiently degrades these anti-pseudomonals:

A

ticarcillin and piperacillin

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11
Q

Name the anti-staphylococcal penicillins:

A

Methicillin, Nafcillin, Oxacillin, Dicloxacillin

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12
Q

Methicillin, Nafcillin, Oxacillin, and Dicloxacillin are drugs of choice for ___

A

penicillin-resistant BUT methicillin-sensitive organisms S aureus (MSSA)

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13
Q

Methicillin is not used clinically d/t this toxicity:

A

interstitial nephritis

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14
Q

What is the route, clearance, and toxicity associated with Nafcillin/

A

IV

hepatic, biliary

Hypersensitivity, Increase P450 induction

Oxacillin and Dicloxacillin each are PO, Renal/biliary, and both cause hypersensitivity

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15
Q

Methicillin and related anti-staphylococcal penicillins bind to __ involved in cell wall synthesis in MSSA

A

penicillin binding proteins

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16
Q

Alteration of __ gene and __ in S. aureus confers high-level resistance to Methicillin, oxacillin and other anti-staph penicillins despite the fact that they are not substrates for B lactamase. This is known as MRSA

A

mec A

PBP2

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17
Q

MRSA is due to alteration of ___ and not caused by B lactamase enzymes

A

PBPs (PBP2)

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18
Q

what is the drug of choice for MRSA?

A

Vancomycin

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19
Q

what are vancomycin uses for Gram +?

A

MRSA (S aureus)
MRSE (S epidermidis)
Enterococci (E faecalis, E faecium) –> avoid overuse to avoid vancomycin resistance
Special use to treat C difficile –> oral admin for topical effect in bowel (if metronidazole failed)

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20
Q

what activity does vancomycin have against gram - aerobes or anaerobes

A

no activity

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21
Q

Vancomycin binds to D-ala-D-ala blocking ___ elongation and cross-linking

A

peptidoglycan

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22
Q

list some vancomycin adverse effects:

A

Vanc-induced erythroderma or shock
Neprhotoxicity and ototoxicity
Dermatologic-rash
Phlebitis at injection site

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23
Q

These penicillins enter via porins, bind to PBPs in periplasm and disrupt cell wall integrity

A

extended spectrum Aminopenicillins –> Ampicillin and Amoxicillin

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24
Q

What gram + cocci and diseases are clinically indicated for extended spectrum aminopenicillins?

A

Gram + cocci: S pneumo, S pyogenes, S viridans, Enterococci

Respiratory infx –> CAP, sinusitis, bronchitis, pharyngitis. Amoxicillin is active against penicillin sensitive S pneumonia and often used for pharyngitis in children because of “taste”

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25
Q

what gram - org and diseases are clinically indicated for extended spectrum aminopenicillins?

A

H influenza: bronchitis in COPD

26
Q

what would you add to ampicillin if there is resistance d/t B lactamase?

A

Sulbactam –> irreversibly inactivates enzyme; depletes B lactamase activity; spares ampicillin; Sulbactam has no inrinsic Abx effect

Ampicillin plus sulbactam - IV

27
Q

what would you add to amoxicillin if there is resistance d/t B lactamase?

A

Clavulanic acid

Amoxicillin plus clavulanic acid - PO

28
Q

List the antipseudomonal penicillins:

A

Ticarcillin

Piperacillin

29
Q

What populations are at risk for Pseudomonas aeruginosa infx?

A

Burn pts
CF pts
Injection drug users
immunosuppressed

30
Q

Ticarcillin and Piperacillin cover these orgs in addition to pseudomonas aeruginosa

A

Gram - rods

Enterobacter spp., E coli, proteus mirabilis, H influenza

31
Q

which anti-pseudomonal is most potent?

A

piperacillin

32
Q

what are some resistance mechanisms employed by pseudomonas aeruginosa?

A

altered PBPs

porin deficit- multi-drug resistance (MDR)

33
Q

In what clinical scenarios would you use ticarcillin and piperacillin together with a B lactamase inhibitor?

A

Severe pneumonia in hospitalized pt with structural lung disease (COPD)
Neutropenic fever-sepsis
Aspiration pneumonia in hospitalized pt, or stroke victim

For empirical therapy of serious infx

34
Q

Which B lactamase inhibitor can you add to Ticarcillin? Pipericillin?

A

Ticarcillin plus clavulanic acid

Pipericillin plus tazobactam

35
Q

All Gen 1-3 cephalosporins are ineffective and lack activity against:

A
  • Listeria monocytogenes
  • Legionella spp
  • Atypical mycoplasma
  • MRSA
  • Enterococci
36
Q

what are the 1st generation cephalosporins?

A

Cefazolin (parenteral, IV, IM) –> penetrates well into bone
CEPHALEXIN (PO) –> 2x daily for pharyngitis
Cephradrine (Parenteral and PO)

37
Q

1st generation cephalosporins have a useful spectrum of activity against:

A

gram + cocci, streptococci and staph aureus

NOT active against: MRSA, MRSE, enterococci

38
Q

what are clinical uses of 1st generation cephalosporins?

A

Surgical prophylaxis if skin flora are likely pathogens; soft tissue and skin infx d/t S aureus, S pyogenes

39
Q

what are the 2nd generation cephalosporins?

A

Cefoxitin (IV, IM)–> active vs anaerobes, eg, B fragilis
Cefotetan (IV, IM) –> same as above
CEFACLOR (PO) –> serum sickness in peds
CEFUROXIME AXETIL (PO) –> poor substrate for B lactamase

40
Q

2nd generation cephalosporins have a useful spectrum of activity against

A

Enhanced activity against Gram - orgs, i.e., E coli, Klebsiella, H influenza; Moraxella cattharalis, proteus spp

41
Q

what are clinical uses of 2nd generation cephalosporins?

A

If facultative gram - bacteria and anaerobes are likely pathogens, i.e., intra-abdominal and gynecological sepsis, surgical prophylaxis for intra-abdominal & colorectal surgery

42
Q

List the 3rd generation cephalosporins:

A

Ceftriaxone –> Long t1/2 ~8 hrs, 1x daily; Penetrates CSF and bone; Activate vs N gonorrhea; Biliary clearance
Cefotaxime –> Enters CSF; useful for meningitis d/t H influenza, S pneumonia, N meningitidis
Cetazidime –> active vs pseudomonas aeruginosa
Cefaperzone –> Disulfiram like alcohol intolerance

43
Q

3rd generation cephalosporins have a useful spectrum of activity against:

A

comparable to 1st generation vs S aureus, S pneumo, S pyogenes. Enhanced activity vs Gram - rods, enteric orgs

44
Q

This 3rd gen cephalosporin is given IV, IM with a t1/2 ~8 hrs, recommended for therapy of penicillin-resistant gonorrhea, Lyme disease involving the CNS or joints, meningitis d/t ampicillin-resistant H influenza and meningitis in children

A

Ceftriaxone

Biliary excretion

45
Q

This 3rd gen cephalosporin is given IV, IM, penetrates well in CNS and is useful for bacterial meningitis from covered orgs such as H influenza, S pneumo, N meningitis, and Gram - enteric bacteria

A

Cefotaxime

renal elimination tubular secretion

46
Q

This 3rd gen cephalosporin is particularly active against P aeruginosa and is an effective therapy for serious infx d/t P aeruginosa when the org is resistant to anti-pseudomonal penicillins or the pt is penicillin allergic.

A

Ceftazidime

47
Q

Ceftazidime should generally be given in combo with __ for tx of serious P aeruginosa

A

aminoglycoside (Tobramycin)

48
Q

What is a 4th generation cephalosporin?

A

Cefepime (IV, IM) –> activity greater than or equal to cefotaxime vs Gram - bacteria, H influenza, N gonorrhea, N meningitidis; Excellent penetration into CSF; Its activity is about = to Ceftazidime vs pseudomonas aeruginosa

49
Q

What is Cefepime (4th gen cephalosporin) insensitive to?

A

many B lactamases

50
Q

why is Cefepime able to better penetrate through outer membrane of gram - bacteria?

A

+charged quaternary ammonium

51
Q

What are adverse effects of cephalosporins?

A

Hypersensitivity (immediate=anaphylaxis, bronchospasm, urticaria; DTH=rash)

Disulfiram-like rxn: nausea, flushing, headache; Disulfirm inhibits aldehyde dehydrogenase

52
Q

Cefotetan and Cefaperazone should be used with caution in these pts:

A

pts taking warfarin or with coagulation abnormalities –> MTT side chain causes reduction in vitamin K-producing bacteria in GI tract - Hypoprothrombinemia and bleeding

53
Q

Name a Monobactam:

A

Aztreonam

54
Q

Aztreonam binds to __ of gram - rods

A

PBP3

55
Q

What is the activity spectrum (which Gram - rods) of Aztreonam and when are they taken?

A

Gram - rods: Klebsiella, Pseudomonas, Serratia, etc

Substitute for extended spectrum penicillin or gen 3,4 cephalosporins if these are contraindicated b/c of hypersensitivity

56
Q

what are your options for empirical therapy covering serious gram - infections if the pt has a severe allergy to penicillins?

A

Aztreonam (IV, IM; it is a monobactam)

inactive vs Gram + spp and anaerobes

57
Q

Name Carbapenems:

A

Imipenem/Cilastatin (not a carbepanem but given alongside to avoid nephrotoxicity)

58
Q

This type of abx is the broadest spectrum of abx available and cover gram + (including Enterococcus faecalis and listeria); gram - orgs (including H influenza, N gonorrhea, Enterobacteriaceae and P aeruginosa); anaerobes, including B fragilis

A

Carbapenems

not degraded by B lactamases

59
Q

This carbapenem is metabolized by the kidney to a nephrotoxic metabolite

A

Imipenem

60
Q

what are adverse effects of Carbapenems?

A

Hypersensitivity and rash
CNS toxicity-seizures, confusion
Nephrotoxicity-Imipenem. Always used with cilastatin

61
Q

This drug is used in combo with Imipenem and inhibits the dipeptidase enzyme in the proximal tubule to minimize nephrotoxicity of Imipenem

A

Cilastatin

Respiratory Medicine-Unit 1 (6 decks)

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