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Antimicrobial Families Flashcards

1
Q

Physiochemical properties of beta-lactams

A
  • water soluble, organic acids (extracellular)
  • low to high protein binding
  • acid labile
  • metal ions can accelerate degradation process
  • chemically incompatible with aminoglycosides in vitro
  • initial fermentation product
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2
Q

Mechanism of action for beta lactams

A

Inhibit bacterial cell wall synthesis by binding to penicillin binding proteins
- cross linkage of peptidoglycan cell wall does not occur

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3
Q

Beta-lactams are typically ______ due to osmotic imbalance

A

Bacteriocidal

- bacteria cytoplasm is hypertonic compared to host isotonic environment

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4
Q

When does static action occur with beta lactams?

A

If bacteria treated with beta-lactams are in an environment isotonic to their cytoplasm

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5
Q

Which antibiotic class has decreased activity in the presence of purulent debris?

A

Beta lactams

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6
Q

MRSA implies resistance to _______

A

The entire beta lactam family

- resistance factors also carry resistance to a variety of other antibiotics

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7
Q

How does cefazolin differ from other first‐generation cephalosporins?

A

Is the only injectable 1st generation cephalosporin

  • has better activity against E coli
  • must be tested for gram neg susceptibility
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8
Q

Mechanisms of beta lactam resistance

A
  • degradation by bacterial enzymes
  • penicillin binding site alteration
  • reduced penetration (impaired crypticity)
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9
Q

What allows passage of resistance between species of bacteria and between genera?

A

Plasmids and transposons

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10
Q

What is the pharmacodynamics of penicillins?

A

Time-dependent killing

- you are not looking at how high peak concentration is

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11
Q

What beta-lactam is measured in units?

A

Penicillin G

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12
Q

All beta lactams concentrate in _______

A

Urine

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13
Q

What is the drug of choice for most streps and anaerobes?

A

Penicillin

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14
Q

What are the 3 forms of penicillin G and their concentrations?

A 
Crystalline (IV,IV,SQ)
- rapid high conc
- short duration
Procaine (IM,SQ)
- flip-flop kinetics
- lower conc, prolonged duration
Benzathene (IM)
- flip flop kinetics
- extremely low conc, prolonged duration (increased residue in food animals)
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15
Q

Penicillin G - adverse reactions

A

Nontoxic, primarily allergic rxns due to degradation product of penicilloic acid
- may have toxicity with salt (potassium pen G) or ester (procaine)

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16
Q

Why should pen G not be used in guinea pigs, hamsters, or rabbits?

A

Will disrupt hind gut flora

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17
Q

How is penicillinase-resistant penicillins similar to pen G?

A

Similar in structure, but is not inactivated by penicillinase
- use against staph that are resistant due to penicillinase

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18
Q

What 2 drugs are used to test bacteria against penicillinase-resistant penicillins?

A

Oxacillin or cefoxitin

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19
Q

Dicloxacillin

A 
Acid stable (can be given orally)
- approved for use in dogs, but 1st gen cephalosporins are used instead
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20
Q

Cloxacillin

A

Intramammary infusion for dairy cows

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21
Q

What are the 2 narrow spectrum penicillins?

A

Pen G and Penicillinase-resistant penicillin

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22
Q

What allows broad spec penicillins better penetration of gram negs?

A

Increased crypticity

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23
Q

What are the 3 broad spec penicillins

A
  • ampicillin
  • amoxicillin
  • hetacillin
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24
Q

Hetacillin

A

Prodrug converted to ampicillin by metabolism

- used as intramammary infusion

25
Ampi and amoxicillin
Used interchangeably - acid stable (oral) - similar D, M, E as narrow specs
26
Which broad spec is absorbed twice as well orally in dogs and cats as ampicillin?
Amoxicillin
27
No _______ are absorbed orally in horses
Penicillins
28
Injectable broad spec penicillins
Sodium ampi and sodium amoxi are given by all parenteral routes - rapid absorption and elimination (given every 8 hrs) - repository trihydrate formulation used in vet med
29
How effective are the broad spec penicillins against enteric gram-neg?
Ampi/amoxicillin is unlikely to reach effective concentrations - S breakpoint in dogs/cats: 0.25 mcg/ml - S breakpoint in cattle: 0.03 mcg/ml
30
Adverse reactions to broad spectrum penicillins
- large doses of ampi can cause diarrhea in horses (entry into bile) - disrupts flora if given orally to ruminants - trihydrate form too irritating to use in horses
31
When is it okay to give oral amoxi (extra-labelly) to a ruminant?
Only give to calves in their first 24 hrs while they are still considered to be a monogastric
32
Extended spectrum penicillins
Anti-pseudomonal penicillins - increased crypticity, bind to altered PBP - ticarcillin, piperacillin - acid labile (6-8 hr dosing interval)
33
Potentiated penicillins
Penicillinase inhibitor is added to formulation to "release" penicillin (ticarcillin, piperacillin) - clavulanic acid, sulbactam - inhibitor looses stability once hydrated, so need to have tablets well wrapped - only works in bacteria resistant by virtue of penicillinase - ineffective against bacterial strains containing type 1 beta-lactamases
34
What potentiated penicillin is effective against chlamydia in cats?
Clavamox
35
With cephalosporins, activity against anaerobes is ______
Erratic | - clostridia are highly resistant
36
1st generation cephalosporins
Not affected by penicillinase, good activity against staph - used in skin and bone infections - not reliable against anaerobes
37
1st gen cephalosporin agents
- cephalothin - nepthrotoxic! still used for in vitro susceptibility test - cephalexin and cefadroxil - used as orals in small animals - cefazolin - better e coli activity than other 1st gens - cephapirin - intramammary infusion for dairy cows
38
Which 1st gen ceph is injectable?
Cefazolin
39
2nd generation cephalosporins
- cefoxitin | - cefotetan
40
Cefoxitin and cefotetan
Have good anaerobic acitivty! - 4 quadrant coverage!! - are structurally considered to be cephamycins (other cephalosporins are cephems) making them less suceptible to cephalosporinase produced by anaerobes - injectable only (IV, IM)
41
What is an injectable, 4 quadrant drug of choice in a non-critical patient
Cefoxitin
42
What 3rd gen cephalosporin is effective against pseudomonas?
Ceftazidime
43
What causes resistance to 3rd gen cephalosporins to pseudomonas?
Extended spectrum beta-lactamases | - increasing public health concern
44
Common 3rd gen injectables
- cefotaxime - ceftriaxone (standard for meningitis) - ceftazidime
45
What allows 3rd gens to cross the BBB?
Low MICs and low to moderate protein binding | - considered drug of choice for bacterial meningitis
46
What cephalosporins are not effective against carbapenem-resistant enterobacteriaceae?
4th gen, 5th gen, and potentiated cephalosporins | - not used in vet med
47
New-gen cephalosporins
Extensively protein bound causing long elimination half-lives and long dosing intervals - goon non-enteric gram neg activity
48
Ceftiofur
Rapidly metabolized to desfuroylceftiofur | - most activity comes from metabolite
49
Cefpodoxime proxetil
Prodrug converted by intestinal wall esterases to active cefpodoxime
50
Cefovecin
Structurally is a 3rd gen, but high protein binding
51
Naxcel
Ceftiofur sodium - requires reconstitution with a limited shelf life - 4 day withdrawal for slaughter * no withdrawal for milk*
52
Excenel
Ceftiofur HCL - shelf stable formulation - 2 day slaughter withdrawal *no milk withdrawal* - exception: spectramast intramammary infusion that does have a milk withdrawal
53
Excede
Ceftiofur crystalline free acid - approved for cattle for 1 or 2 doses - -> 13 day slaughter withdrawal, no milk withdrawal - approved in swine (14 day slaughter withdrawal) and horses
54
Cefpodoxime proxetil
Once daily oral dosing | - dogs used to treat skin and soft tissue infections
55
Cefovecin
Labelled for skin and soft tissue infections due to staph, strep, and pasturella and for UTI due to e coli - long duration due to high protein binding and long half life
56
Monobactams
Spectrum limited to aerobic gram-neg bacilli
57
Carbapenems
Broadest spectrum of activity of any antibiotics - penetrates BBB, inflammation enhances penetration - imipenem and meropenam
58
Meropenem
Does not cause seizures or nephrotoxicity | - given SQ and IV
59
Carbapenem-resistant enterobacteriaceae
Enterobacteriaceae resistant to all beta-lactams including carbapenems - reported in all 50 states - resistant mechanisms: carbapenemases, decreased crypticity, active efflux pump - horizontal transmission

Pharmacology 1 (15 decks)

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