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Cell Wall Inhibitors
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Cell Wall Inhibitors

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Questions and Answers

What is the common structural feature of penicillins and cephalosporins?

  • A 3-member ring
  • A 6-member ring
  • A 5-member ring
  • A 4-member ring (correct)

    • Which of the following is NOT a type of β-Lactam antibiotic?

  • Cephalosporins
  • Penicillins
  • Vancomycin (correct)
  • Daptomycin

    • What is the primary mechanism of action of penicillins and cephalosporins?

  • Inhibiting bacterial cell wall synthesis (correct)
  • Inhibiting DNA replication
  • Inhibiting protein synthesis
  • Inhibiting bacterial membrane function

    • Which of the following antibiotics is available only in oral formulation?

    <p>Fosfomycin</p> Signup and view all the answers

    What is the main classification of antibiotics that includes penicillins and cephalosporins?

    <p>β-Lactam antibiotics</p> Signup and view all the answers

    Which of the following is NOT a cell wall inhibitor?

    <p>Polymyxin</p> Signup and view all the answers

    Why are piperacillin and ticarcillin often used in combination with penicillinase inhibitors?

    <p>To enhance their activity</p> Signup and view all the answers

    Which of the following penicillins can be administered orally?

    <p>Penicillin V</p> Signup and view all the answers

    What is the effect of food on the absorption of penicillinase-resistant penicillins?

    <p>Food decreases the absorption of these penicillins</p> Signup and view all the answers

    What is the role of procaine penicillin G and benzathine penicillin G?

    <p>They serve as depot forms</p> Signup and view all the answers

    Why are the antibacterial effects of piperacillin and ticarcillin limited?

    <p>They are susceptible to penicillinases</p> Signup and view all the answers

    What is the effect of oral administration of penicillins on the intestinal flora?

    <p>It affects the composition of the intestinal flora</p> Signup and view all the answers

    What is the primary use of certain penicillins?

    <p>Treatment of known or suspected staphylococcal infections</p> Signup and view all the answers

    What is a characteristic of methicillin-resistant staphylococcus aureus (MRSA) and S. epidermidis (MRSE)?

    <p>They are resistant to all penicillins</p> Signup and view all the answers

    What is the result of combining ampicillin with inhibitors of penicillinases?

    <p>The antibacterial activity is enhanced</p> Signup and view all the answers

    Which of the following organisms is not susceptible to ampicillin and amoxicillin?

    <p>Pseudomonas</p> Signup and view all the answers

    What is the effect of combining ampicillin with aminoglycosides in enterococcal and listerial infections?

    <p>Synergistic</p> Signup and view all the answers

    Which of the following penicillins has activity against Pseudomonas?

    <p>Piperacillin</p> Signup and view all the answers

    What is a characteristic of third-generation cephalosporins?

    <p>Ability to penetrate the blood-brain barrier</p> Signup and view all the answers

    Which of the following infections is typically treated with second-generation cephalosporins?

    <p>Sinus, ear, and respiratory infections caused by H influenzae or M catarrhalis</p> Signup and view all the answers

    Which of the following cephalosporins is active against penicillin-resistant pneumococci?

    <p>Ceftriaxone</p> Signup and view all the answers

    Which of the following is a clinical use of cephalosporins?

    <p>Surgical prophylaxis in selected conditions</p> Signup and view all the answers

    Which of the following cephalosporins is used to treat gonorrhea?

    <p>Ceftriaxone</p> Signup and view all the answers

    Which of the following organisms is typically susceptible to second-generation cephalosporins?

    <p>H influenzae</p> Signup and view all the answers

    What is the primary mechanism of action of polymyxins?

    <p>Disrupting bacterial cell membrane integrity</p> Signup and view all the answers

    Why is daptomycin not recommended for the treatment of pneumonia?

    <p>It is inactivated by pulmonary surfactants</p> Signup and view all the answers

    What is the advantage of fosfomycin in treating urinary tract infections?

    <p>It maintains high concentrations in the urine over several days</p> Signup and view all the answers

    Which of the following bacteria is NOT typically resistant to polymyxins?

    <p>K.pneumoniae</p> Signup and view all the answers

    What is a potential adverse effect of daptomycin?

    <p>Myopathy</p> Signup and view all the answers

    What is the spectrum of activity of daptomycin?

    <p>Similar to vancomycin, but active against vancomycin-resistant strains</p> Signup and view all the answers

    What is the primary mechanism of action of fosfomycin?

    <p>Inhibition of cell wall synthesis</p> Signup and view all the answers

    Which of the following bacteria is fosfomycin effective against?

    <p>E. coli</p> Signup and view all the answers

    What is the advantage of daptomycin over vancomycin?

    <p>It is active against vancomycin-resistant strains</p> Signup and view all the answers

    What is the primary use of daptomycin?

    <p>Treatment of complicated skin and skin structure infections</p> Signup and view all the answers

    Why should daptomycin not be used to treat pneumonia?

    <p>It is inactivated by pulmonary surfactants</p> Signup and view all the answers

    What is the mechanism of action of polymyxins?

    <p>Disruption of cell membrane integrity</p> Signup and view all the answers

    Which of the following bacteria is inherently resistant to polymyxins?

    <p>Proteus spp.</p> Signup and view all the answers

    What is the characteristic of polymyxins that makes them concentration-dependent bactericidal agents?

    <p>They have a detergent-like effect on the cell membrane</p> Signup and view all the answers

    What is a common side effect of fosfomycin?

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

    What laboratory test should be monitored when using daptomycin?

    <p>Creatine Phosphokinase</p> Signup and view all the answers

    Study Notes

    Penicillins

    • Susceptible to penicillinases, often used in combination with penicillinase inhibitors (e.g., tazobactam, clavulanic acid) to enhance activity
    • Classification: derivatives of 6-aminopenicillanic acid, contain a beta-lactam ring structure essential for antibacterial activity
    • Mechanism of Action:
      • Binding of the drug to specific enzymes (penicillin-binding proteins [PBPs]) in bacterial cytoplasmic membrane
      • Inhibition of transpeptidation reaction that cross-links linear peptidoglycan chain constituents of the cell wall
      • Activation of autolytic enzymes that cause lesions in the bacterial cell wall

    Narrow-Spectrum Penicillinase-Susceptible Agents

    • Penicillin G: prototype, used for infections caused by common streptococci, meningococci, gram-positive bacilli, and spirochetes
    • Penicillin V: oral drug used mainly for oropharyngeal infections
    • Activity against enterococci is enhanced by coadministration of aminoglycosides

    Very-Narrow-Spectrum Penicillinase-Resistant Drugs

    • Methicillin, nafcillin, and oxacillin: used for treatment of known or suspected staphylococcal infections
    • Methicillin-resistant staphylococcus aureus (MRSA) and S. epidermidis (MRSE) are resistant to all penicillins and often resistant to multiple antimicrobial drugs

    Wider-Spectrum Penicillinase-Susceptible Drugs

    • Ampicillin and amoxicillin: have a wider spectrum of antibacterial activity than penicillin G
      • Clinical uses include indications similar to penicillin G, as well as infections resulting from enterococci, Listeria monocytogenes, Escherichia coli, Proteus mirabilis, Haemophilus influenzae, and Moraxella catarrhalis
      • Synergistic with aminoglycosides in enterococcal and listerial infections
    • Piperacillin and ticarcillin: have activity against several gram-negative rods, including Pseudomonas, Enterobacter, and in some cases Klebsiella species
      • Susceptible to penicillinases, often used in combination with penicillinase inhibitors (e.g., tazobactam, clavulanic acid) to enhance activity

    Routes of Administration

    • Combination of ampicillin with sulbactam, piperacillin with tazobactam, and anti-staphylococcal penicillins nafcillin and oxacillin: administered intravenously (IV) or intramuscularly (IM)
    • Penicillin V, amoxicillin, and dicloxacillin: available only as oral preparations
    • Depot forms: procaine penicillin G and benzathine penicillin G administered IM, slowly absorbed into circulation and persist at low levels over a long time period

    Absorption

    • Most penicillins are incompletely absorbed after oral administration, affecting the composition of the intestinal flora
    • Food decreases absorption of penicillinase-resistant penicillins due to stomach acid, so they should be taken on an empty stomach

    Other Antibiotics

    Fosfomycin

    • Excreted by the kidney, with urinary levels exceeding minimal inhibitory concentrations (MICs)
    • Indicated for urinary tract infections caused by E. coli or E. faecalis
    • Adverse effects include diarrhea, vaginitis, nausea, and headache

    Daptomycin

    • Bactericidal, novel cyclic lipopeptide with spectrum similar to vancomycin but active against vancomycin-resistant strains of enterococci and staphylococci
    • Indicated for treatment of complicated skin and skin structure infections and bacteremia caused by S. aureus
    • Inactivated by pulmonary surfactants, so it should never be used in the treatment of pneumonia
    • Creatine phosphokinase should be monitored since daptomycin may cause myopathy

    Polymyxins

    • Cationic polypeptides that bind to phospholipids on the bacterial cell membrane of gram-negative bacteria
    • Have a detergent-like effect that disrupts cell membrane integrity, leading to leakage of cellular components and cell death
    • Concentration-dependent bactericidal agents with activity against most clinically important gram-negative bacteria, including P. aeruginosa, E. coli, K. pneumoniae, Acinetobacter spp., and Enterobacter spp.
    • However, alterations in the cell membrane, lipid polysaccharides allow many species of Proteus and Serratia to be intrinsically resistant

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    Cell Wall Inhibitors (2).pdf

    Description

    Test your knowledge on cell wall inhibitors, including penicillins, cephalosporins, and other beta-lactam antibiotics, as well as vancomycin, fosfomycin, and daptomycin. This quiz covers the basics of cell wall inhibitors and their mechanisms of action.

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