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Exam ASC306 > AB II - classes & use > Flashcards

AB II - classes & use Flashcards

1
Q

What is penicillins MOA?

A

Mechanism of action: interfere/block bacterial enzymes essential for assembly of bacterial cell wall peptidoglycan (only effective against actively dividing bacterial colony)

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2
Q

Why is penicillin effective against gram +ves but not gram -ves?

A

gram +ves have more peptidoglycan that penicilin disrupts -> osmotic lysis of bacteria
while gram -ves have far less

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3
Q

describe penicillins spectrum of activity. Eg’s…

A

Normal - narrow spectrum: (penicillin-G) target mainly gram +ves & anaerobes
Broad-spectrum: (amoxicillin, ampicillin) same as ‘normal’ but also some gram -ves, E.coli, proteus
Others - Extended-spectrum (ticarcillin); Beta-lactamase stable penicillins eg. methicillin

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4
Q

Species considerations of penicillin…?

A 
Amoxycillin-clavulanic acid 'clavulox' (smallies) NOT for small herbivores
Procaine penicillin (horses, cattle, dogs, cats)
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5
Q

Resistance status of beta-lactams?

A

gram -ves - cell wall is less permeable

beta-lactamases & penicillinases - both of which Staphylococcus aureus have

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6
Q

What is MRSA?

A

Methicillin Resistant S. aureus - a common nosocomial infection

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7
Q

Approaches to combating β-lactamase positive bacteria?

A

beta-lactamase inhibitors such as clav -> irreversibly binds to beta-lactamase thus sparing the first active beta-lactam “suicide inhibitor”
combined as amoxyclav

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8
Q

toxicity and residue concerns of β-lactams…?

A

very safe for oldies, juvies, during preg. and lactation
SE via dysbiosis: GIT signs, diarrhoea, vomiting
small herbivores

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9
Q

Define dysbiosis…

A

microbial imbalance inside body (digestive tract) from killing ‘good’ bacteria

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10
Q

The most commonly dispensed AB in humans & small animals?

A

Amoxyclav

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11
Q

Describe Staphylococcus aureus (“Golden Staph”) historical resistance to Penicillin G

A

1940- 100% susceptible1944- 1st beta-lactamase strains appear1967- 1st methicillian resistant S.aureus (MRSA)1993- MRSA widely distributed

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12
Q

do beta-lactams have a high toxicity?why or why not.

A

no.very safe can be sued in geriatrics, juveniles, pregnancy and during lactation.because side effects usually come about through dysbiosis- killing good bacteria, toxins, GIT signs (diarrhoea and vomiting most common)

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13
Q

One of the most commonly dispensed ABs in largie practice?

A

procaine penicillin

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14
Q

For gentamicin (aminoglycoside), describe the mechanism and spectrum of activity, species application, route and frequency of administration, indications/contraindications for use and potential side-effects

A
  • Mechanism of action: inhibits bacterial ribosomes & prevents normal amino acid synthesis
  • Spectrum of activity: highly effective against aerobic bacteria; ineffective against anaerobic bacteria
  • Species application: equine med
  • Route & freq. of admin: mostly parenterally (injected); some are orally administered & need to stay in intestinal tract. Once daily dose (q24h)
  • Indications: highly effective against aerobic bacteria
  • contraindications/side effects: neonates, food animals, animals with hypomotility, animals with intestinal disease as increased time in the gut; nephrotoxic & ototoxic (ear)
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15
Q

Which largie is gentamycin most commonly used in?

A

horse

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16
Q

Chemistry, pharmacokinetics and effects on clinical use of aminoglycosides?

A
  • hydrophillic at most physiological pH levels thus -> administered parenterally (via injection) as absorption across GI tract limited after oral admin -> stays in GIT longer
  • well absorbed thru abraded (damaged) skin also stays in uterus & bladder if treating infections there
  • remains mostly in extracellular fluid thus >in neonates & young
  • hydrophillic glycosides don’t cros BBB thus -> high in bronchial secretions used to treat pneumonia
  • accumulate in kidneys & inner ear -> toxicity
  • most excreted via kidney (kidney disease = increase t1/2 = [plasma drug] = toxicity; IV fluid therapy = decreased t1/2)
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17
Q

2 common classes of aminoglycosides and indications?

A

used in equine…gentamycin (most common) & amikacin (less resistance) streptomycin (banned in Aus)

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18
Q

For enrofloxacin (quinolone), describe the mechanism and spectrum of activity, species application, route and frequency of administration, indications/contraindications for use and potential side-effects

A
  • Mechanism of action: interfere with DNA gyrase -> preventing bacterial DNA supercoiling (DNA storage form) -> disrupting DNA function
  • Spectrum of activity: common gram -ve & gram +ve bacteria in skin, resp, urinary infections; beta-lactamase bacteria (Pseudomonas, staph, E.coli, Salmonella spp.); inconsistent against Streptococcus spp.; ineffective against anaerobic bacteria
  • Species application: dogs & cats & any species really! bacterial DNA gyrase different from human gyrase thus safe for use in humans
  • Route & freq. of admin: oral or injectable q24h
  • Indications: common gram -ve & gram +ve bacteria in skin, resp, urinary infections; beta-lactamase bacteria (Pseudomonas, staph, E.coli, Salmonella spp.)
  • contraindications/side effects: small & medium sized dogs aged 2 & 8 months; young horses; oral admin. with antacids; bubbles in joint cartilage/degeneration (growing young animals); seizures; blindness (cats)
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19
Q

What bacteria are fluoroquinolones not effective against?

A

Streptococcus spp.

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20
Q

Which animals should fluoroquinolones not be used in? why?

A

livestock animals for eating because development of resistance to quinolones in human bacteria and impact of drug residues in human food

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21
Q

describe approaches to combating beta-lactamase positive bacteria

A

1.Beta-lactamase inhibitors- use of 2nd beta-lactam that will irreversibly bind to the 2.beta-lactamase- used as a beta-lactamse inhibitor

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22
Q

Info about macrolide tylosin?

A

bacteriostatic AB for bovine pneumonia; targets + ve bacteria & mycoplasma Pasteurella spp. & moderate efficacy against anaerobes
can be bacteriocidal at [high]
MOA: inhibit protein synthesis via tRNA & also bind to P site of subunit 50s ribosome
Admin. route: IM or SC and in-feed

23
Q

list the there classes of beta-lactam penicillin antibiotics and some examples

A
  1. Natural penicillins - narrow spectrum; predominantly gram positives and anaerobes (e.g. staphylococcus)- Penicillin G, benzylpenicillin2. Aminopenicillins- broader spectrum, as above plus some gram negatives; E-coli and proteus - amoxycillin, ampicillin3. Others- beta-lactamase stable penicillins, e.g. methicillin, cloxacillin, extended spectrum.
24
Q

list penicillin toxicity and residual concerns

A

..

25
Q

Describe Staphylococcus aureus (“Golden Staph”) historical resistance to Penicillin G

A

1940- 100% susceptible1944- 1st beta-lactamase strains appear1967- 1st methicillian resistant S.aureus (MRSA)1993- MRSA widely distributed

26
Q

do beta-lactams have a high toxicity?why or why not.

A

no.very safe can be sued in geriatrics, juveniles, pregnancy and during lactation.because side effects usually come about through dysbiosis- killing good bacteria, toxins, GIT signs (diarrhoea and vomiting most common)

27
Q

what is the most commonly dispensed antibiotic in humans and small animals?

A

amoxycillin- clavulanic acid

28
Q

list some considerations with clavulanic acid and if it is still affective in the presence of beta-lactamse

A

yes it is affective in presence of beta-lactamsekeep refrigerated, can be given IM and SC NEVER IVlabel dose is often considered too low.

29
Q

describe penicillins basic chemistry and pharmacokinetics

A

Pharmacokinetics:- rapid absorption - t1/2 usually short (under hr) therefore repository salts utilised in parenteral formulations- good distribution except for eye, prostate and non-inflamed CNS

30
Q

describe penicillins spectrum of activity

A

Spectrum of activity: normal-spectrum (penicillin-G); broad-spectrum (amoxicillin, ampicillin); extended-spectrum (ticarcillin)

31
Q

list some of penicillins species considerations

A

-horses if given orally die, IM ok (as with other larger herbivores)- cannot be given to small herbivores; cecum to small t diffuse out slowly and all of their good bacteria in their digestive tract is killed rapidly - easier with non-fermemnters.

32
Q

describe penicillins resistance status

A

..

33
Q

what is beta-lactamse?

A

a mechanisms of resistance produced by bacteria. can chop up and knock out penicillin G

34
Q

describe approaches to combating beta-lactamase positive bacteria

A

1.Beta-lactamase inhibitors- use of 2nd beta-lactam that will irreversibly bind to the 2.beta-lactamase- used as a beta-lactamse inhibitor

35
Q

What are the two beta-lactam antibiotics used

A
  1. Penicillins 2. Cephalosporins
36
Q

list the there classes of beta-lactam penicillin antibiotics and some examples

A
  1. Natural penicillins - narrow spectrum; predominantly gram positives and anaerobes (e.g. staphylococcus)- Penicillin G, benzylpenicillin2. Aminopenicillins- broader spectrum, as above plus some gram negatives; E-coli and proteus - amoxycillin, ampicillin3. Others- beta-lactamase stable penicillins, e.g. methicillin, cloxacillin, extended spectrum.
37
Q

list penicillin toxicity and residual concerns

A

..

38
Q

Describe Staphylococcus aureus (“Golden Staph”) historical resistance to Penicillin G

A

1940- 100% susceptible1944- 1st beta-lactamase strains appear1967- 1st methicillian resistant S.aureus (MRSA)1993- MRSA widely distributed

39
Q

do beta-lactams have a high toxicity?why or why not.

A

no.very safe can be sued in geriatrics, juveniles, pregnancy and during lactation.because side effects usually come about through dysbiosis- killing good bacteria, toxins, GIT signs (diarrhoea and vomiting most common)

40
Q

list some considerations with clavulanic acid and if it is still affective in the presence of beta-lactamse

A

yes it is affective in presence of beta-lactamsekeep refrigerated, can be given IM and SC NEVER IVlabel dose is often considered too low.

41
Q

describe penicillins basic chemistry and pharmacokinetics

A

chemistry: penicillin has a beta-lactan ring (bacteria like staph have resistance as they have enzymes (beta-lactamases) that attacks the ring)
Pharmacokinetics:
- rapid absorption
- t 1/2 usually short (under hr) therefore repository salts utilised in parenteral formulations
- good distribution except for eye, prostate and non-inflamed CNS

42
Q

Species considerations of penicillin…?

A 
Amoxycillin (smallies)
Procaine penicillin (horses, cattle, dogs, cats)
43
Q

Approaches to combating β-lactamase positive bacteria?

A

beta-lactamase inhibitors such as clav -> irreversibly binds to beta-lactamase thus sparing the first active beta-lactam “suicide inhibitor”

44
Q

toxicity and residue concerns of β-lactams…?

A

very safe for oldies, juvies, during preg. and lactation

45
Q

The most commonly dispensed AB in humans & small animals?

A

Amoxyclav

46
Q

Info about β-lactam amoxyclav… lots

A 
gram +ve & excellent anaerobic coverage
works against many β-lactamase producing bacteria
convenient dosing (SID)
keep in fridge
good tissue dist.
IM or SC NEVER IV!
20mg/kg
not reg'd in horses or prod. animals
47
Q

Info about β-lactam procaine penicillin… lots

A

gram +ve & excellent anaerobic coverage
does NOT work against β-lactamase producing bacteria
convenient dosing (SID)
keep in fridge
IM or SC NEVER IV!
long acting (with procaine or benzathine as insoluble salts) 3day action

48
Q

One of the most commonly dispensed ABs in largie practice?

A

procaine penicillin

49
Q

Which largie is gentamycin most commonly used in?

A

horse

50
Q

2 common classes of aminoglycosides and indications?

A

used in equine…gentamycin (most common) & amikacin (less resistance) streptomycin (banned in Aus)

51
Q

What bacteria are fluoroquinolones not effective against?

A

Streptococcus spp.

52
Q

Which animals should fluoroquinolones not be used in? why?

A

livestock animals for eating because development of resistance to quinolones in human bacteria and impact of drug residues in human food

53
Q

For oxytetracycline, describe the mechanism and spectrum of activity, species application, route and frequency of administration, indications/contraindications for use and potential side-effects

A
  • Mechanism of action: bind to bacterial ribosomes & prevent tRNA linking to it -> disrupt protein synthesis
  • Spectrum of activity: broad spectrum (bacteriostatic antimicrobial - ie does not directly kill bacteria)
  • Species application: production animals
  • Route & freq. of admin: injection (IM), q2-3 days
  • Indications: Rickettsial disease; Mycoplasma pneumonia, chlamydial infection
  • contraindications/side effects: not to give with bacteriocidals (eg. penicillins or cepholasporins); 1st few weeks of animals life (tooth issues); oral admin. -> superinfections; horses -> cardiac problems, collapse & death
54
Q

Safety concerns of macrolide tilmicosin? target & duration of effect?

A

injection may be fatal to humans

72h activity against Pasteurella single injection

Exam ASC306 (2 decks)

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