Questions and Answers
What is the basic functional structure of Penicillin?
Beta lactam ring
How do Beta lactam antibiotics kill bacteria?
They block biosynthesis of peptidoglycan layer by blocking the transpeptidation step resulting in cell lysis.
Penicillins have a structural similarity to what molecule that partially explains their activity?
ACYL-D-ALANYL-D-ALANINE
All cell wall inhibitors are what class of antibiotics with one exception, which is?
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Beta Lactams include?
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What are some of the limitations of Penicillin G?
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Penicillins are soluble in what?
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Penicillins are rapidly excreted in the urine by what mechanism(s)?
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In order to maintain stable plasma levels, how must the drug be dosed/administered?
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Can Penicillin penetrate the meninges to access the CSF? Give an example of when this is not the case.
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The first attempts to extend the half life of Penicillins was by the cocurrent administration of probenecid which acts how?
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By using probenecid to decrease renal tubular secretion, how does this increase the effect of penicillins?
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Benzylpenicillin is an example of what?
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Penicillin salts are often administered how?
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Instead of Na+ or Cl-, what is used as the counter-ion to benzylpenicillin? Why?
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What is the role of benzathine?
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Changing the benzyl to a Phethoxy-methyl improves absorption of penicillins how?
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Penicillin G refers to? Penicillin V?
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Ampicillin and Amoxicillin are examples of what?
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What is an advantage of aminopenicillins?
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Aminopenicillins can be administered in what manner? Why?
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Are aminopenicillins more or less efficient in killing gram - bacteria? Why?
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What are the two main pathways antibiotics can take through the outer membrane?
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What is an example of a general diffusion porin that is a major route of entry for Beta lactam antibiotics?
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Ampicillin docks at what portion of the OmpF porin monomer? Mutation in this area can lead to what?
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In order to treat serious gram negative infections, what two subclasses of penicillins were developed?
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What are the advantages of these extended spectrum penicillins?
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Ticarcillin and Ticarcillin clavulanate are examples of what class of penicillins?
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How must carboxypenicillins be administered? Why?
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Study Notes
Beta Lactam Antibiotics Overview
- Penicillin's functional structure is characterized by a beta lactam ring.
- Beta lactam antibiotics eliminate bacteria by disrupting peptidoglycan layer biosynthesis, leading to cell lysis via transpeptidation blockade.
- They structurally resemble acyl-D-alany-D-alanine, aiding in their antibacterial activity.
Types and Limitations of Penicillins
- All cell wall inhibitors are primarily beta lactams with the exception of vancomycin.
- Beta lactam classes include penicillins, cephalosporins, aztreonam, and carbapenems.
- Limitations of Penicillin G: short half-life, narrow spectrum (mainly gram-positive), acid instability, and susceptibility to beta-lactamases.
Pharmacokinetics of Penicillins
- Penicillins are water-soluble and rapidly excreted in urine, primarily via active tubular secretion and to a lesser extent through glomerular filtration.
- High doses and frequent administration are necessary to maintain stable plasma levels.
- Penicillins can penetrate the meninges during inflammation, but not otherwise.
Enhancements and Forms of Administration
- Probenecid extends penicillin's half-life by blocking renal tubular secretions.
- Benzylpenicillin is classified as a penicillin salt and is typically administered intramuscularly.
- Procaine is used as a counter-ion in benzylpenicillin to reduce pain and enhance IM administration by decreasing solubility.
- Benzathine further reduces salt form solubility of Benzylpenicillin.
Variants of Penicillins
- Phethoxy-methyl modification increases acid resistance of penicillins.
- Penicillin G is known as benzylpenicillin, while Penicillin V is phenoxy-methyl penicillin.
- Ampicillin and amoxicillin belong to aminopenicillins, featuring a broader spectrum that includes more gram-negative bacteria.
Efficiency and Administration Routes
- Aminopenicillins can be taken orally due to their acid stability and are more effective against gram-negative bacteria because they penetrate cell walls more efficiently.
- Antibiotics can penetrate the outer membrane via lipid-mediated pathways for hydrophobic drugs or general diffusion porins for hydrophilic drugs, such as OmpF porrin.
Resistance and Advanced Penicillins
- Ampicillin interacts with the OmpF porrin's constriction zone, where mutations can confer resistance.
- Extended spectrum penicillins developed for serious gram-negative infections include alpha carboxy penicillin (Ticarcillin) and acylamino-penicillin (Piperacillin).
- These provide better penetration across the gram-negative membrane and higher affinity for penicillin-binding proteins (PBPs), also known as "anti-pseudomonal penicillins."
Specific Classes and Administration of Penicillins
- Ticarcillin and Ticarcillin clavulanate are categorized as carboxypenicillins and must be administered intravenously or intramuscularly due to poor oral absorption.
- Piperacillin is another example of a subtype within penicillins, involving mechanisms specific to treatment regimens.
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Description
Test your knowledge on beta lactam antibiotics, including their functional structure, types, and pharmacokinetics. This quiz covers the mechanisms by which these antibiotics work, as well as their limitations and classification. Perfect for students learning about microbiology and pharmacology.
