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44 Cards in this Set
- Front
- Back
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State the mechanism of action of the B-lactams:
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-3D analogs of d-Ala-D-Ala linkage in PG side chains, -competitive ligand inhibitors of Transpeptidases (PBPs) by covalently binding them.
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What effect does inhibition of the Transpeptidase PBPs in bacteria have?
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It prevents crosslinking of Peptidoglycan, which weakens the cell wall and results in osmotic lysis.
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What additional mechanism do the B-lactams have?
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Stimulate murein hydrolases - lytic enzymes - which enhances crosslink breakdown.
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What are 3 main properties of B-lactams as a group?
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-Bactericidal (static under some conditions)
-Effective against both GP/GN -Activity is maximal on actively growing bacteria |
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What is the implication of the fact that the B-lactam's action is maximal on actively growing bacteria?
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If it is given as part of a drug combo with a static agent and the B-lactam is discontinued, the static drug won't likely be effective.
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What are 3 mechanisms of resistance to B-lactams? Which is most prevalent?
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-B-lactamase (most prevalent)
-Altered target PBPs -Prevention of B-lactam from getting to target site |
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Is one organism's b-lactamase equal to another's?
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No - there are differences in how they're encoded; some are inducible.
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How does Alteration of PBPs confer resistance to B-lactam drugs?
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It prevents the B-lactam from effectively BINDING to the transaminase PBPs
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What organisms often prevent the B-lactam drugs from even reaching PBPs?
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Gram negatives - this is their intrinsic resistance.
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What are the 4 subclasses of B-lactam antibacterials?
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-Penicillins
-Cephalosporins -Imipenem -Aztreonam |
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What is the distribution of penicillins in the body like in general?
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They distribute well to most areas, but have low CSF penetration.
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When does CSF penetration by the penicillins increase?
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During meningitis
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What is the half-life of the Penicillins like in general?
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Short
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How are the penicillins eliminated/metabolized?
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30% - liver
20% - glom filtration 80% - tubular excretion (OAT) |
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What do you have to be careful in giving Penicillins?
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Adverse reactions!
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What are 8 toxic side effects that can be seen with Penicillins?
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FRENDLAS
-Fever -Rash -Enterocolitis -Nephritis -Diarrhea!!! 25% -Liver enzyme elevation -Allergy/anaphylaxis -Seizures |
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What is the incidence of anaphylactic reactions to penicillins?
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Low incidence - but very important to remember because it does occur in some people.
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Which toxic side effect of Penicillins has the highest incidence?
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Diarrhea
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What antibacterials actually cause diarrhea/enterocolitis?
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All of those that have access to the GI tract.
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Which penicillin is especially associated with causing nephritis?
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Methicillin
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What 2 penicillin drugs are only administered by IV or IM?
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-Penicillin G
-Ticarcillin |
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What 4 penicillin drugs are administered ORALLY?
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-Penicillin V
-Amoxicillin -Ampicillin -Oxacillin |
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Though the penicillins generally have short half-lives, what 2 forms increse the half-life substantially?
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-Procaine
-Benzathine penicillin |
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Why is Penicillin V able to be administered orally, where Penicillin G cannot be?
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Pen V is more acid stable
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What organisms are Penicillin G/V effective against?
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Both gram pos and gram negs (if the latter don't produce B-lactamase)
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For what 4 bugs are Penicillin G/V the drugs of CHOICE for?
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-Anaerobes (except B. fragilis)
-Strep pneumo/most streps -Neisseria meningitidis -T. pallidum, syphilis (think of PANTS) |
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For what 3 other organisms do the penicillins have GOOD activity against?
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-Anthrax
-Listeria -Actinomyces |
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Which penicillin is for B-lactamase producing staphylococci?
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Oxacillin
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What is Oxacillin less effective for?
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Streps that can be treated with Penicillin G, and gram negatives.
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Which penicillins are effective for treating various B-lactamase NEGATIVE gram pos AND gram neg organisms?
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Ampicillin
Amoxicillin |
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What gram negs are included in the spectrum of Ampicillin and Amoxicillin?
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-Neisseria
-E. coli -Salmonella -Haemophilus |
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What b-lactamase neg gram pos organisms are included in the spectrum of Ampicillin and Amoxicillin?
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-Streptococci
-Listeria |
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Which penicillin has BROAD gram neg effectiveness?
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Ticarcillin
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What is another important thing to remember about Ticarcillin?
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It is only administered by IV/IM like Penicillin G.
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What are 3 gram negs included in the spectrum of Ticarcillin?
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-Pseudomonas aeruginosa
-Enterobacter -Proteus |
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What other penicillin has broad gram-neg spectrum including those bugs that resist Ticarcillin?
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Piperacillin
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Which of the broad-spectrum GN penicillins can also kill gram positives?
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Only Ticarcillin - not Piperacillin.
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What should you always do for a patient prior to giving them a penicillin drug for the first time?
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A pre-penicillin skin test to determine if they are allergic.
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What type of drugs will decrease the elimination of penicillins in general? Why?
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Anionic drugs like Probenecid; because they compete for the organic anion transporter at the renal tubules.
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What penicillin drug is the drug of choice for otitis media in otherwise healthy children?
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Amoxacillin
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What would make you pick Amoxacillin over Ampicillin?
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Amoxacillin is better absorbed orally
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What would make you pick Ampicillin over Amoxacillin?
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-Ampicillin can treat Meningitis bc it is available for IV infusion (amox is not)
-Ampicillin can treat GI infections via low absorption so it stays in GI tract longer |
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How is Piperacillin administered?
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By injection
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What is a specific bug that Piperacillin can treat that Ticarcillin doesn't?
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Klebsiella
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