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PR3151 > Pharmacology - Bacterial Cell Wall Synthesis Inhibitors > Flashcards

Pharmacology - Bacterial Cell Wall Synthesis Inhibitors Flashcards

1
Q

What are the categories of bacterial cell wall synthesis inhibitors?

A
  • Beta lactams (Penicillins, Cephalosporins, Carbapenems, Monobactams)
  • Glycopeptides (Vancomycin)
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2
Q

What are the 4 subclasses of penicillins?

A
  • Natural penicillins
  • Penicillinase-resistant penicillins
  • Aminopenicillins
  • Anti-pseudomonal penicillins
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3
Q

What is the mechanism of action of the beta lactams?

A

Bind to the active site of transpeptidase enzyme (aka penicillin binding protein) which catalyses the cross-linking of the terminal peptide components of linear polymer chains

This inhibits with peptidoglycan synthesis to exert bactericidal effect, by weakening cell wall structure, to build up intracellular osmotic pressure, resulting in cell lysis

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4
Q

What is the route of admin for Penicillin G?

A

Potassium: IV
Procaine: IM
Benzathine: IM

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5
Q

What is the route of admin for Penicillin V?

A

PO

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6
Q

What is the spectrum of action of the natural penicillins?

A

Mostly Gram Positives: Streptococcus spp, Enterococcus fecalis, Finegoldia magna (may work against some strains of MSSA, use AST to determine)

Some Gram Negatives: Meningococci, Gonococci

Must be beta lactamase negative

Pen G Benzathine used for syphilis

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7
Q

Are the natural penicillins able to penetrate the CSF?

A

Acceptable

Penetration increases if meninges are inflammed

Pen G potassium reaches higher concentrations than procaine or benzathine

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8
Q

How are the natural penicillins excreted?

A

Renal, largely by tubular secretion, as unchanged parent drug

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9
Q

How can cloxacillin be administered?

A

IV/IM/PO

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10
Q

What is the spectrum of action of cloxacillin?

A

Cover most penicillinase producing staphylococci especially MSSA
Can also be used as empiric therapy of Streptococcus (except S. pneumoniae)

INEFFECTIVE against Gram negative
All are less effective against microorganisms susceptible to penicillin G

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11
Q

Can cloxacillin penetrate the CSF well?

A

No

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12
Q

How is cloxacillin excreted?

A

Renal

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13
Q

How are the aminopenicillins administered?

A

PO or IV

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14
Q

Which broad spectrum penicillin has better oral bioavailability?

A

Amoxicillin

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15
Q

What is the spectrum of action of the broad spectrum penicillins?

A

Good penetration for Gram negative

Indicatied for B-lactamase negative strains as monotherapy

Empiric use against Streptococcus spp (incl S. pneumoniae), Enterococcus fecalis and Finegoldia magna acceptable

No coverage of Pseudomonas or Klebsiella
(do not use for empiric Gram negative coverage)

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16
Q

Do the broad spectrum penicillins penetrate CSF well?

A

Yes, but only by IV
Penetration increases w inflamed meninges

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17
Q

How are the broad spectrum penicillins excreted?

A

Renal, as unchanged drug in urine

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18
Q

How is piperacillin administered?

A

IV

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19
Q

What is the spectrum of activity of piperacillin-tazobactam?

A

Greater activity than other penicillins against Gram negative - can use as empiric Tx for Bacteriodes fragilis, Hemophilus influenzae, E.coli, Klebsiella, P. mirabilis and Pseudomonas aeruginosa

Gram positives that can be treated empirically: MSSA, Streptococcus spp (incl S.pneumoniae), Enterococcus fecalis and Finegoldia magna

Increased anaerobic coverage

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20
Q

Is piperacillin able to penetrate the CSF?

A

Yes, if meninges are inflamed

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21
Q

How is piperacillin excreted?

A

Primarily renal - 70% excreted unchanged in urine

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22
Q

How do the beta lactamase inhibitors work?

A

Inactivate beta lactamases by binding to the beta lactamase to inactivate it

Clavulanic acid: binds covalently to restructure the beta lactamase to permanently inactivate

Sulbactam and Tazobactam: irreversibily bind to beta lactamase at or near its active site to protect the beta lactam antibiotics

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23
Q

What are the beta lactam and beta lactamase inhibitor pairings?

A
  • Amoxicillin clavulanate
  • Ampicillin Sulbactam
  • Piperacillin Tazobactam
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24
Q

How are the beta lactam and beta lactamase inhibitor pairs administered?

A
  • Amoxicillin clavulanate: PO/IV
  • Ampicillin Sulbactam: IV
  • Piperacillin Tazobactam: IV
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25
Q

What is the spectrum of action of amoxicillin clavulanate?

A

Effective against B-lactamase producing strains of staphylococci, H. influenzae, gonococci and E. coli

Empiric use acceptable: MSSA, Streptococcus spp (incl S. pneumoniae), Enterococcus fecalis, Finegoldia magna, Bacteriodes fragills, H. influenzae, E coli, Klebsiella, P. mirabilis

Used in skin, LRTI and UTI

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26
Q

Can amoxicillin clavulanate be used for CSF?

A

Use is discouraged, penetration is only moderate

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27
Q

How is amoxicillin clavulanate excreted?

A

Renal, as unchanged drug in urine

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28
Q

What is the spectrum of action of ampicillin sulbactam?

A

Effective against B-lactamase procuding strains of S. aureus, Gram negative aerobes, and anaerobes
Used in skin, intra-abdominal and gynecologic infections

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29
Q

Can ampicillin sulbactam be used for CSF?

A

Only when there is meningeal inflammation

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30
Q

How is ampicillin sulbactam excreted?

A

Renal, as unchanged drug in urine

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31
Q

Can piperacillin tazobactam be used for CSF?

A

Use is discouraged, penetration is modest only

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32
Q

How is piperacillin tazobactam excreted?

A

Renally
Piperacillin as unchanged drug, Tazobactam as both parent drug and metabolites in urine

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33
Q

Do the penicillins need to be dose adjusted?

A

Yes, for renal function

34
Q

What are the adverse reactions of the penicillins?

A
  1. Allergy/Hypersensitivity
    - contraindicated for previous anaphylactic reactions or serious skin reactions
  2. GI Sx - N/V, CDAD
  3. Neurotoxicity - convulsions, coma at v high doses due to renal failure
35
Q

What generation of cephalosporin does cefazolin belong to?

A

1st

36
Q

How is cefazolin administered?

A

IM/IV/Eye drop

37
Q

What generation of cephalosporins does cephalexin belong to?

A

1st

38
Q

How is cephalexin administered?

A

PO

39
Q

Which generations of cephalosporins are administered orally and parenterally respectively?

A

PO: 1st and 2nd gen
IV/IM: 3rd, 4th, 5th

40
Q

What are the advantages of the 3rd, 4th and 5th generation cephalosporins as compared to the 1st and 2nd generations?

A
  1. Higher CSF penetration
  2. Higher Gram Negative coverage
  3. Greater resistance against beta lactamase producing strains
41
Q

What is the spectrum of coverage of the 1st gen cephalosporins?

A

V active against Gram positives - Streptococci (Except penicillin resistant strains eg S. pneumoniae), S. aureus (Except MRSA)

Poor coverage against Gram negatives and B-lactamase positive bacteria

Also acceptable as empiric therapy for Finegoldia magna, Hemophilus influenzae, E coli, Klebsiella and P mirabilis

42
Q

What are the microbes that 1st and 2nd generation cephalosporins are ineffective against?

A
  1. Pseudomonas aeruginosa AND

LAME
Listeria monocytogenes
Atypicals (Mycoplasma, Chlamydia, Legionella)
MRSA
Enterococcus spp

43
Q

What generation of cephalosporins does cefuroxime belong to?

A

2nd

44
Q

What is the spectrum of action of cefuroxime?

A

Less active than 1st generation against Gram positive, but slightly more active against Gram negatives

Empiric use acceptable: MSSA, Streptococcus spp (incl S. pneumoniae), Finegoldia magna, Hemophilus influenzae, E coli, Klebsiella, P mirabella

45
Q

What generation of cephalosporins does ceftriaxone belong to?

A

3rd

46
Q

What generation of cephalosporins does ceftazidime belong to?

A

3rd

47
Q

What is the spectrum of action of ceftriaxone?

A

MSSA, Streptococcus spp (incl S. pneumoniae), Finegoldia magna, Hemophilus influenzae, E coli, Klebsiella, P mirabilis

Do not cover LAME

48
Q

What is the spectrum of action of ceftazidime?

A

Finegoldia magna, E coli, Klebsiella, P mirabilis, Pseudomonas aeruginosa

Do not cover LAME

49
Q

What generation of cephalosporins does cefepime belong to?

A

4th

50
Q

What is the spectrum of action of cefepime?

A

MSSA, Streptococcus spp (incl S. pneumoniae), Finegoldia magna, Hemophilus influenzae, E. coli, klebsiella , P. mirabilis, Pseudomonas aeruginosa

51
Q

What generation of cephalosporins does ceftaroline belong to?

A

5th

52
Q

What is the spectrum of action of ceftaroline?

A

MRSA, VRSA, MSSA, Streptococcus spp (incl S. pneumoniae), Finegoldia magna, Hemophilus influenzae, E coli, Klebsiella, P. mirabilis, Moraxella catarhalis

53
Q

How are the cephalosporins cleared?

A

Renally, except for ceftriaxone that is cleared hepatically

54
Q

Which cephalosporins do not cover LAME?

A

1st, 2nd, 3rd, 4th generations

55
Q

Which cephalosporins cover Pseudomonas aeruginosa?

A

Ceftazidime, Cefepime

56
Q

What are the adverse effects of the cephalosporins?

A
  1. Hypersensitivity - low frequency of cross reactions with penicillins, but avoid if pt has Hx of serious hypersensitivity reactions with penicillin eg anaphylaxis, serious skin reactions
  2. GI Sx - V/D, colitis/CDAD
57
Q

What is cilastatin?

A

DHP1 inhibitor

Used with Imipenem as imipenem is hydrolysed rapidly by DHP1

58
Q

What do carbapenems mainly cover

A

Extended Spectrum B Lactamase (ESBL) producing bacteria

59
Q

How are the carbapenems administered?

A

IV

60
Q

List the names of the 3 carbapenems.

A

Imipenem
Meropenem
Ertapenem

61
Q

Which carbapenem can penetrate the CSF?

A

Meropenem

62
Q

What is the spectrum of action of imipenem?

A

Active against Streptococci (incl penicillin-resistant S. pneumoniae), Enterococci (excl E. faecium), staphylococci (incl penicillinase-producing strains), most strains of Pseudomonas, Finegoldia magna and anaerobes incl Bacteriodes fragilis

CTeng: Also can use as empiric Tx for Haemophilus influenzae. E. coli, Klebsiella, Enterobacter (Amp-C producign GNR)

63
Q

What is the spectrum of action of meropenem?

A

Activity similar to imipenem, w activity against some imipenem-resistant P. aeruginosa strains, but less activity against Gram positive cocci
Can use in children w meningitis >3months old

CTeng: Also can use as empiric Tx for Haemophilus influenzae. E. coli, Klebsiella, Enterobacter (Amp-C producign GNR)

64
Q

What is the spectrum of action of ertapenem?

A

Similar activity to imipenem except it lacks activity agains P. aeruginosa and Enterococcus species

65
Q

How are the carbapenems excreted?

A

Renal

Imipenem as metabolite (which can be nephrotoxic)
Meropenem and Ertapenem excreted mostly unchanged

66
Q

What are the adverse effects of the carbapenems?

A
  1. Hypersensitivity - cross allergy to penicillins possible but suggested to be potentially low, avoid w Hx of anaphylaxis or serious skin reactions to penicillins
  2. GI Sx - V/D, possible CDAD
  3. Neurotoxicity - seizures with high blood concentrations of carbapenems, resulting from high doses and renal impairments
67
Q

How is aztreonam administered?

A

IM/IV

68
Q

What is the spectrum of activity of aztreonam?

A

ONLY AGAINST GRAM NEGATIVES
NO ACTIVITY AGAINST GRAM POSITIVE AND ANAEROBES
Useful against many B-lactamase positive gram negative bacteria

69
Q

Is aztreonam able to penetrate the CSF?

A

Yes, if the patient has inflammed meninges

70
Q

How is aztreonam excreted?

A

Renal, unchanged in urine

71
Q

What are the adverse reactions of aztreonam?

A

Generally well tolerated but can cause occasional skin rashes and transaminasemia

72
Q

Which of the beta lactams exhibit cross reactivity with penicillin?

A

Cephalosporins, carbapenems

73
Q

How is vancomycin administered?

A

IV

PO only for problems in GIT, eg CDAD - v poor PO bioavailability

74
Q

What is the spectrum of activity of vancomycin?

A

Primarily acts on Gram positives - MSSA, MRSA, Streptococci (incl penicillin resistant & sensitive strains), Bacillus species, Clostridium species, Enterococcus

Not active against all Gram negatives - molecule too large to enter cell

Commonly used for osteomyelitis, endocarditis, pts w serious infections but allergic to penicillins, prophylaxis where MRSA is expected, CDAD (via PO, 1st line)

75
Q

How is vancomycin excreted?

A

Renally, mostly as unchanged drug

76
Q

What are the adverse reactions for vancomycin?

A
  1. Thrombophlebitis w fever, chills (swelling at admin site)
  2. Red man syndrome - rash above nipple line, can be accompanied by hypotension, infuse over longer time of 1-2h to avoid
  3. Nephrotoxicity and ototoxicity - rare but risk increaed when used w other nephro/ototoxic agents
77
Q

What is the mechanissm of resistance underlying MRSA?

A

Altered penicillin binding protein, which most of the beta lactams do not have a good affinity for

78
Q

What is the mechanism of action of vancomycin?

A

Inhibits cell wall peptidoglycan synthesis by acting against NAM-NAG transglyccosylation

79
Q

What are the mechanisms of resistance to penicillin?

A
  1. Altered PBP w reduced affinity for penicillins
  2. Production of beta lactamases
  3. Decreased ability of antibiotic to reach PBP when bacteria decreases porin production
  4. Efflux pumps
80
Q

What are the mechanisms of resistance to vancomycin?

A

expression of enzymes that modify bacterial cell wall precursors

PR3151 (14 decks)

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