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31 Cards in this Set
- Front
- Back
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What are the three broad classes of beta-lactams? |
Penicillins Cephalosporins Carbapenems |
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What is the MOA of the beta-lactams? |
Transverses cell wall and reaches plasma membrane. Once there binds to penicillin-binding protein leading to disrupted cell wall synthesis. Bacteria then loses capacity to osmoregulate and thus lysis occurs. |
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Are the beta lactams dose or time-dependant? |
Time-dependant |
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Are the beta lactams bactericidal or bacteriostatic? |
Bactericidal |
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What types of bacteria are beta lactams inherently less effective against and which classes are the exception to that rule? |
Gram negative bacteria 3rd generation cephalosporins and extended specturm penicillins |
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How do some bacteria avoid being killed by beta lactams? |
Production of beta lactamases (or penicillinases) Mutation of penicillin-binding protein leading to decreased beta lactam affinity (MRSA) |
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How can the effects of the beta lactamase producing bacteria be overcome? |
Producing beta lactamase-stable beta lactams (methicillin) Combining beta lactams with beta lactamase inhibitiors (amoxycillin-clavulonic acid) |
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What are the 4 classes of penicillins? |
Natural penicillins Aminopenicillins Beta lactamase-stable penicillins Extended spectrum penicillins |
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What is an example of a natural penicillin and what type of bacteria are they not effective against? |
Procanine penicillin, benzylpenicillin Gram -ve aerobes (ie E. coli, Salmonella, Yersinia, Pseudomonas, Campylobacter) Resistant gram +ves (penicillinase producing Staph. spp) |
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What is an example of a aminopeinicillin and how do they differ from natural penicillins? |
Amoxycillin, ampicillin Capacity to kill some common gram -ve aerobes (E. coli, Proteus) |
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What is an example of a beta lactamase-stable penicillin? |
Methicillin, cloxacillin |
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What is an example of an extended spectrum penicillin and what is confusing about this class' name? |
Ticarcillin, piperacillin Doesn't actually have an extended spectrum. Has increased efficacy against gram -ves (esp. Pseudomonas) but decreased efficacy against gram +ves. |
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Which class of cephalosporins is not commonly used? |
Second generation cephalosporins |
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What is an example of a first generation cephalosporin and what class is it comparable to? |
Cephalexin, cefazolin Aminopenicillins (decreased anaerobic activity but increased staphylococcus activity) |
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What is an example of a third generation cephalosporin and what types of bacteria is it effective against? |
Ceftiofur, ceftazidime, cefovecin Effective against gram -ves but less effective against gram +ve |
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What is the significance of the carbapenems and what is their spectrum of activity? |
Reserve drug class Effective against all types of bacteria except those with mutated penicillin-binding proteins (ie MRSA or VRE) |
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Describe the significant pharmacokinetic properties of the beta lactams? |
- Rapid absorption (often have insoluble salts added to increase DOA) - Short half life (as above) - Good distribution (useful for treating UTI as often passed through urine in un-metabolised form) |
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What concerns are there for toxicity with the beta lactams? |
Generally safe to humans due to selective toxicity of MOA Dysbiosis (very concerning in small herbivores with reliance on gut flora) IV administration (additives ie procaine or coconut oil can be lethal if given IV) |
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What is Amoxycillin-Clavulanic Acid and what preparations does it come in? |
Aminopenicillin with beta lactamase-inhibitor added to avoid resistance Injectible (not IV due to coconut oil), oral tablet and liquid |
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What is Ampicillin and what preparation does it come in? |
Aminopenicillin Powder that is reconstituted into liquid which can then be given IV |
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What is Benzylpenicillin and what preparation does it come in? |
(similar to procaine penicillin but in SA) Natural penicillin Powder that is reconstituted into liquid which can then be given IV |
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What is cephazolin and what preparation does it come in? |
1st generation cephalosporin Powder that is reconstituted into liquid which can then be given IV (similar to aminopenicillins but with decreased anaerobic activity and increased staph activity |
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What is Ticarcillin-clavulanic acid and what is it effective against? |
Extended-spectrum penicillin Narrow specrum of activity, essentially just Pseudomonas spp. |
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What is procaine penicillin and what is it used against? |
Natural penicillin with procaine added to increased DOA - Acidic so doesn't concentrate in mammary tissue. Procaine also makes it toxic if given IV (causes fatal arrhythmias) Gram +ve aerobes and all anaerobes |
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What is the significance of combining benzathine penicillin with procaine penicillin? |
Benzathine increases DOA even further than procaine, leading to upto 3 day DOA |
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What is cephalexin and what is it used for? |
1st generation cephalosprorin (similar to aminopenicillin - less effective against anaerobes but more effective against staph.) Often used for treatment of secondary Staph. psedintermedius infection |
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What is cefovecin and what is its significance? |
3rd generation cephalosporin (effective more so against gram -ves) Extremely long DOA (2 wks) due to decreased clearance caused by high degree of protein binding. Only effective in cats and dogs |
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What is ceftiofur, what is it used for an what is the significance of its WHP? |
3rd generation cephalosporin used in LAs More effective against gram -ves than procaine penicillin 0-day milk WHP due to not being able to reach mammary tissue. If given intramammary than WHP is void. |
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What are the risks of using long-acting antibiotics and why is this more so an issue in long-acting ceftiofur than in cefovecin? |
May lead to selection for resistance as long-acting antibiotics are often in sub-MIC concentrations while they are wearing off. Ceftiofur more so an issue as is used in production animals which may lead to introduction of resistant bacteria into food chain. |
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What is Penethamate and what about its composition makes it well suited for providing targeted therapy? |
Penicillin Is an alkaline penicillin and so concentrates and persists in the acidic environment created during mastitis |
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What is the difference between dry-cow intramammaries and lactating-cow intramammaries? |
Dry-cow intramammaries often has much longer milk WHP (50 days compared to 1-3). If accidentally given to a lactating cow, milk from that cow will have to be discarded for much longer than would otherwise have to be. |
