Beta-Lactam Antibiotics: Penicillins and Mechanism of Action
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Questions and Answers

What is the mechanism of action of beta-lactam antibiotics?

  • Inhibition of protein synthesis
  • Inhibition of cell wall synthesis by binding to specific receptors (PBPs) and inhibiting transpeptidase enzymes (correct)
  • Disruption of cell membrane function
  • Inhibition of DNA replication

What is the effect of beta-lactamase on the activity of beta-lactam antibiotics?

  • Increases antibacterial activity
  • Has no effect on antibacterial activity
  • Converts beta-lactam antibiotics to a more active form
  • Decreases antibacterial activity (correct)

Which of the following is a characteristic of penicillin G?

  • It is resistant to gastric acid (correct)
  • It is resistant to beta-lactamase
  • It is primarily excreted in the bile
  • It is a broad-spectrum antibiotic

What is the purpose of combining beta-lactam antibiotics with beta-lactamase inhibitors?

<p>To prevent the degradation of the antibiotic by beta-lactamase (D)</p> Signup and view all the answers

Which of the following is a use of procaine and benzathine penicillin G?

<p>Treatment of syphilis (D)</p> Signup and view all the answers

What is the half-life of penicillin G?

<p>30 minutes to 1 hour (C)</p> Signup and view all the answers

What is the main difference between penicillin and cephalosporins?

<p>Penicillin has a beta-lactam ring, while cephalosporins have a dihydrothiazine ring. (A)</p> Signup and view all the answers

What is the main mechanism of resistance to penicillin?

<p>Hydrolysis by beta-lactamase. (B)</p> Signup and view all the answers

Which of the following antibiotics is used to treat Staphylococcal infections?

<p>Methicillin. (C)</p> Signup and view all the answers

What is the main advantage of using Piperacillin and Ticarcillin over Ampicillin and Amoxicillin?

<p>They are more effective against Gram-negative organisms. (C)</p> Signup and view all the answers

What is the main characteristic of 3rd generation cephalosporins?

<p>They are more effective against Gram-negative organisms. (D)</p> Signup and view all the answers

What is the main route of elimination for most cephalosporins?

<p>Renal tubular excretion. (D)</p> Signup and view all the answers

What is the mechanism of action of Clindamycin?

<p>Binding to the 50S ribosomal subunit (D)</p> Signup and view all the answers

What is the primary route of elimination of Clindamycin?

<p>Hepatic metabolism and renal excretion (D)</p> Signup and view all the answers

Which of the following is a common mechanism of resistance to Clindamycin?

<p>All of the above (D)</p> Signup and view all the answers

What is a common side effect of Clindamycin?

<p>GI irritation (D)</p> Signup and view all the answers

What is a common indication for Clindamycin?

<p>Skin and soft tissue infections (B)</p> Signup and view all the answers

What is the mechanism of action of quinupristin-dalfopristin against gram-positive cocci?

<p>Inhibition of protein synthesis (B)</p> Signup and view all the answers

What is the primary route of excretion for quinupristin-dalfopristin?

<p>Feces (C)</p> Signup and view all the answers

What is the Primary indication for the use of quinupristin-dalfopristin?

<p>MRSA infections (D)</p> Signup and view all the answers

What is the half-life of quinupristin?

<p>0.85 hours (C)</p> Signup and view all the answers

What is the mechanism of resistance to quinupristin-dalfopristin?

<p>All of the above (D)</p> Signup and view all the answers

What is the primary limitation of using linezolid?

<p>Risk of thrombocytopenia (B)</p> Signup and view all the answers

What is the mechanism of action of sulfonamides?

<p>Inhibitors of folic acid synthesis (A)</p> Signup and view all the answers

What is the consequence of displacing bilirubin from plasma protein binding?

<p>Kernicterus in neonates (A)</p> Signup and view all the answers

What is the primary route of excretion for sulfonamides?

<p>Urinary excretion (C)</p> Signup and view all the answers

What is the indication for Sulfasalazine?

<p>Inflammatory bowel diseases (D)</p> Signup and view all the answers

What is the consequence of crystalluria in sulfonamide therapy?

<p>Crystalluria and increased susceptibility to Gram-positive and Gram-negative infections (B)</p> Signup and view all the answers

What is the mechanism of action of Trimethoprim?

<p>Inhibitor of dihydrofolate reductase (A)</p> Signup and view all the answers

What is the consequence of sulfonamide toxicity on the hematological system?

<p>All of the above (D)</p> Signup and view all the answers

What is the indication for Cotrimoxazole?

<p>All of the above (D)</p> Signup and view all the answers

What is the effect of sulfonamides on mammalian cells?

<p>Cause inability to synthesize folic acid (A)</p> Signup and view all the answers

What is the half-life of Sulfamethoxazole?

<p>10-12 hours (B)</p> Signup and view all the answers

Flashcards

Penicillin V

A penicillin derivative particularly effective against infections in the mouth and throat after tooth removal.

Very-Narrow-Spectrum Penicillinase-Resistant Agents

A group of penicillins resistant to breakdown by penicillinase, an enzyme produced by some bacteria.

Methicillin

The first penicillin to be used against staph infections, now often used as a model drug for this purpose.

Methicillin-induced nephritis

A major concern with methicillin, as it can cause inflammation of the kidneys.

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MRSA & MRSE

Bacteria that have evolved to resist the effects of methicillin, posing a significant challenge for treatment.

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Ampicillin and Amoxicillin

Penicillin derivatives with a broader spectrum of activity, effective against a wider range of bacteria.

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Synergistic effect

A phenomenon where two antibiotics work together to achieve a greater effect than when used alone.

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Piperacillin and Ticarcillin

Penicillin derivatives that primarily target gram-negative bacteria, which often cause infections in the lungs and urinary tract.

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Cephalosporins

A class of antibiotics chemically distinct from penicillin.

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Dihydrothiazine ring

A key structural feature of cephalosporins, differentiating them from penicillin.

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Cephalosporin Generations

A common way to classify cephalosporins based on their development, from 1st to 5th generations, with greater effectiveness against specific bacteria as they evolve.

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Cephalexin

A representative drug of the 1st generation of cephalosporins, effective mainly against gram-positive bacteria.

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Pharmacokinetics

A detailed description of how a drug enters the body, circulates, and is eliminated.

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Hepatic metabolism of cephalosporins

Cephalosporins are primarily processed by the liver before being removed from the body.

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Renal tubular excretion of cephalosporins

The main route of elimination for most cephalosporins, involving excretion through the kidneys.

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Ceftriaxone and Cefoperazone

Two cephalosporins that are uniquely eliminated through bile, rather than the kidneys.

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Cephalosporin resistance

The ability of bacteria to develop resistance mechanisms against cephalosporins, often increasing with higher generations.

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Clindamycin

A potent antibiotic binding to the ribosome, disrupting protein synthesis.

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Bacteriostatic Activity

The primary mechanism by which clindamycin exerts its antibacterial effect.

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Anaerobic Infections

Severe infections caused by anaerobic bacteria, which thrive in oxygen-deprived environments.

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Superinfection

One of the potential risks of using clindamycin, where harmful bacteria overgrow, leading to further complications.

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Lincosamides

A class of antibiotics that includes clindamycin, with similar mechanisms and effects.

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Quinupristin/Dalfopristin

A combination of two antibiotics, quinupristin and dalfopristin, specifically effective against resistant bacteria.

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Bactericidal Activity

These antibiotics specifically target the ribosome to disrupt protein synthesis, leading to bacterial death.

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Arthralgia-myalgia syndrome

A serious side effect of quinupristin/dalfopristin, involving pain in joints and muscles.

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CYP3A4

A group of enzymes involved in processing many drugs.

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Oxazolidinones

Antibiotics that inhibit the formation of new proteins in bacteria by binding to the ribosome.

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23S rRNA

A crucial component of the ribosome, the site where oxazolidinones bind to exert their effects.

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Sulfonamides

A subclass of antibiotics that specifically target the synthesis of folic acid, a crucial nutrient for bacterial growth.

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PABA (para-aminobenzoic acid)

A key chemical compound essential for bacterial growth, a target for sulfonamide antibiotics.

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Trimethoprim

Another type of antibiotic that inhibits folic acid synthesis in a different way.

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Cotrimoxazole

A combined therapy using trimethoprim and sulfamethoxazole, enhancing effectiveness against infections.

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Hypersensitivity Reactions

A common side effect of sulfonamides, characterized by an immune response to the drug.

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Beta-lactam Antibiotics

A broad category of antibiotics that target the cell wall of bacteria.

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Transpeptidase enzymes

The primary enzyme inhibited by beta-lactam antibiotics, responsible for building the bacterial cell wall.

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Enzymatic hydrolysis

The breakdown of beta-lactam antibiotics by certain bacteria, leading to resistance to therapy.

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Study Notes

Penicillin and its Derivatives

  • Penicillin V: Effective for oropharyngeal infections following dental extraction.
  • Very-Narrow-Spectrum Penicillinase-Resistant Agents: Includes Methicillin, Nafcillin, and Oxacillin; resistant to penicillinase.
  • Methicillin: Prototype agent for treating staphylococcal infections; known to cause nephritis.
  • Resistance: MRSA (methicillin-resistant Staphylococcus aureus) and MRSE (methicillin-resistant Staphylococcus epidermis) are resistant to methicillin.
  • Ampicillin and Amoxicillin: Broader spectrum; effective against Enterococci, E. coli, H. influenzae, L. monocytogenes (dangerous for pregnant women), P. mirabilis, and M. catarrhalis. Synergistic effect with aminoglycosides.
  • Piperacillin and Ticarcillin: Target gram-negative bacteria, including Pseudomonas, Enterobacter, and Klebsiella species; also show synergy with aminoglycosides.

Cephalosporins

  • Structural Characteristics: Cephalosporins differ from penicillins with a dihydrothiazine ring and acyl side chains (R1 and R2).
  • Generations: Classified based on their development; 1st Generation (Cephalexin, Cefazolin) generally targets Gram-positive bacteria.
  • Pharmacokinetics: Metabolized in the liver, mainly excreted via renal tubular excretion, except Ceftriaxone and Cefoperazone (excreted in bile).
  • Resistance: Cephalosporins exhibit varying resistance profiles from 1st to 3rd Generation, increasing coverage against Gram-negative organisms.

Clindamycin and Lincosamides

  • Clindamycin: Binds to the 50S ribosomal subunit, exhibiting bacteriostatic activity; effective against Gram-positive cocci and anaerobic bacteria.
  • Toxicities: Can lead to severe anaerobic infections, skin rashes, toxic shock syndrome, and superinfections.
  • Combination Therapy: Often paired with aminoglycosides for serious infections such as necrotizing fasciitis.

Streptogramins

  • Quinupristin/Dalfopristin: Bactericidal against most Gram-positive cocci; effective against MRSA and vancomycin-resistant E. faecium.
  • Mechanism: Binds to the 50S ribosomal subunit, causing protein synthesis disruption.
  • Toxicities and Drug Interactions: May cause arthralgia-myalgia syndrome; interacts with drugs metabolized by CYP3A4.

Oxazolidinones

  • Linezolid and Tidezolid: Bind to the 23S rRNA of the 50S ribosomal subunit; prevent ribosome formation and exhibit bacteriostatic activity against streptococci.

Sulfonamides and Trimethoprim

  • Sulfonamides: Bacteriostatic agents that inhibit folic acid synthesis by competing with PABA; used for uncomplicated UTIs and ocular infections.
  • Trimethoprim: Inhibits dihydrofolate reductase, blocking the formation of active tetrahydrofolate.
  • Cotrimoxazole: Combination of trimethoprim and sulfamethoxazole; provides synergistic inhibition of folate synthesis and expanded activity against various infections.
  • Toxicities: Potential for hypersensitivity reactions, gastrointestinal disturbances, and hematologic toxicity.

General Pharmacokinetics and Resistance

  • Basic Mechanism of Action (MOA): Beta-lactam antibiotics disrupt cell wall synthesis by inhibiting transpeptidase enzymes, leading to bacterial cell lysis.
  • Resistance: Common mechanisms include enzymatic hydrolysis by beta-lactamases and modifications in target sites.

Important Considerations

  • Drug Interactions: Some antibiotics displace other drugs from plasma proteins, potentially increasing their free concentrations and toxicity.
  • Adverse Effects: Includes skin toxicity, gastrointestinal upsets, and possible renal implications, necessitating cautious use in specific populations, such as the elderly or with pre-existing conditions.

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Description

This quiz covers the characteristics and mechanism of action of beta-lactam antibiotics, specifically penicillins, including their MOA, pharmacokinetics, resistance, and drug interactions.

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