Cell Wall Inhibitors in Antibiotics
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Questions and Answers

Which drugs are classified as aminopenicillins?

  • Nafcillin and oxacillin
  • Ampicillin and amoxicillin (correct)
  • Piperacillin and tazobactam
  • Methicillin and dicloxacillin

What is the role of β-lactamase inhibitors when co-formulated with aminopenicillins?

  • To prevent resistance in gram-positive bacteria
  • To enhance the antimicrobial spectrum (correct)
  • To weaken the bacterial cell wall
  • To reduce toxicity of the penicillins

Which penicillin is used to identify methicillin-resistant Staphylococcus aureus (MRSA)?

  • Methicillin (correct)
  • Amoxicillin
  • Piperacillin
  • Dicloxacillin

What specifically grants resistance to methicillin-sensitive Staphylococcus aureus (MSSA) against ampicillin and amoxicillin?

<p>β-lactamase production (A)</p> Signup and view all the answers

Which of the following is an antipseudomonal penicillin?

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

What is the major mechanism of resistance to β-lactam antibiotics?

<p>β-lactamase production (B)</p> Signup and view all the answers

What type of infections are antistaphylococcal penicillins primarily used to treat?

<p>Infections caused by penicillinase-producing staphylococci (B)</p> Signup and view all the answers

How can β-lactamase be produced by bacteria?

<p>Constitutionally from the bacterial chromosome or by plasmid transfer (A)</p> Signup and view all the answers

What is the primary mechanism of β-lactam resistance in gram-positive bacteria?

<p>Secretion of β-lactamases extracellularly (A)</p> Signup and view all the answers

How do gram-negative bacteria primarily resist β-lactam drugs?

<p>Inactivation of drugs in the periplasmic space (A)</p> Signup and view all the answers

What factor limits the penetration of β-lactam antibiotics in gram-negative bacteria?

<p>Porin channels in the cell wall (B)</p> Signup and view all the answers

What characteristic of modified PBPs in bacteria contributes to antibiotic resistance?

<p>Lower affinity for β-lactam antibiotics (C)</p> Signup and view all the answers

Which of the following β-lactam antibiotics can be administered orally?

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

What happens to the absorption of dicloxacillin when taken with food?

<p>Decreases due to increased gastric emptying (B)</p> Signup and view all the answers

Which of the following carbapenems can reach therapeutic levels in bacterial meningitis without inflammation?

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

What is the primary route of administration for depot forms of penicillin?

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

What is true regarding the distribution of β-lactam antibiotics?

<p>They generally distribute well throughout the body (B)</p> Signup and view all the answers

What is the primary route of administration for Imipenem?

<p>Intravenously (B)</p> Signup and view all the answers

What adverse effect is more likely to occur at high levels of Imipenem?

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

Which of the following agents is exclusively a monobactam?

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

What type of pathogens does Aztreonam primarily target?

<p>Gram-negative pathogens (C)</p> Signup and view all the answers

Which β-lactamase inhibitor contains a β-lactam ring but has no significant antibacterial activity by itself?

<p>Clavulanic acid (D)</p> Signup and view all the answers

What effect does combining Imipenem with cilastatin have?

<p>Prolongs activity in the body (B)</p> Signup and view all the answers

Which of the following is NOT a known side effect of aztreonam?

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

What is the primary route of excretion for penicillins?

<p>Organic acid tubular secretion and glomerular filtration (A)</p> Signup and view all the answers

Which of the following is true regarding the metabolism of penicillin G?

<p>It undergoes insignificant metabolism. (B)</p> Signup and view all the answers

What effect does probenecid have on penicillin levels in the blood?

<p>It inhibits secretion, thereby increasing blood levels. (D)</p> Signup and view all the answers

What is a common adverse reaction associated with penicillin use?

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

Which β-lactam antibiotic is known to cause nephritis?

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

Which of the following statements is correct about cephalosporins?

<p>They are produced semisynthetically via modification of amino acids. (D)</p> Signup and view all the answers

What is a potential hematologic toxicity associated with prolonged penicillin therapy?

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

In which condition are penicillin levels in the prostate deemed insufficient?

<p>Non-inflamed state (B)</p> Signup and view all the answers

Which type of infection is primarily managed with oral vancomycin?

<p>C.difficile infection in the colon (C)</p> Signup and view all the answers

What is a primary action of lipoglycopeptides like telavancin and oritavancin?

<p>Inhibit bacterial cell wall synthesis (D)</p> Signup and view all the answers

What is a significant adverse effect associated with telavancin?

<p>Nephrotoxicity (B)</p> Signup and view all the answers

What characteristic differentiates oritavancin and dalbavancin from telavancin?

<p>Longer half-life enabling single-dose administration (C)</p> Signup and view all the answers

Daptomycin is primarily used for infections caused by which organisms?

<p>Vancomycin-resistant Enterococcus (VRE) (B)</p> Signup and view all the answers

Which of the following is a unique feature of daptomycin?

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

What is a consequence of the combined actions of lipoglycopeptides?

<p>Minimized selection of resistance (B)</p> Signup and view all the answers

Which property do lipoglycopeptides share with vancomycin?

<p>Poor absorption after oral administration (A)</p> Signup and view all the answers

Which generation of cephalosporins is primarily resistant to staphylococcal penicillinase?

<p>First generation (A)</p> Signup and view all the answers

What is a unique feature of the second generation of cephalosporins?

<p>Activity against anaerobes, including Bacteroides fragilis (A)</p> Signup and view all the answers

Which third-generation cephalosporin is noted for its activity against Pseudomonas aeruginosa?

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

What caution is associated with the use of third-generation cephalosporins?

<p>Increased risk of C. difficile infection (B)</p> Signup and view all the answers

Which fourth-generation cephalosporin must be administered parenterally?

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

What sets the advanced-generation cephalosporin Ceftaroline apart from others?

<p>It is effective against MRSA (D)</p> Signup and view all the answers

Which of the following is not a characteristic of first-generation cephalosporins?

<p>Broad activity against anaerobes (C)</p> Signup and view all the answers

What type of infections is Ceftaroline used to treat?

<p>Complicated skin and skin structure infections (A)</p> Signup and view all the answers

Flashcards

Semisynthetic penicillins

Penicillins modified to treat wider range of bacteria, including certain Gram-negative infections.

Aminopenicillins

A type of semisynthetic penicillin, including ampicillin and amoxicillin, effective against broader range of bacteria.

β-lactamase inhibitors

Chemicals that block the action of bacterial enzymes that destroy penicillins.

Antistaphylococcal penicillins

Penicillins resistant to enzymes that break them down, used to treat staphylococcal infections (e.g., MRSA).

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β-lactamase

Bacterial enzyme that breaks down penicillins, preventing their effectiveness.

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MRSA

Methicillin-resistant Staphylococcus aureus; a type of bacteria resistant to many antibiotics.

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Antipseudomonal penicillins

Penicillins that effectively combat Pseudomonas aeruginosa.

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Antibiotic Resistance Mechanisms

Ways bacteria develop resistance to antibiotics: production of enzymes that break down antibiotics, reduced antibiotic uptake into cells, and changes in antibiotic binding sites.

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Gram-positive β-lactamase secretion

Gram-positive bacteria release β-lactamases outside the cell.

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Gram-negative β-lactam inactivation

Gram-negative bacteria inactivate β-lactam drugs in the periplasmic space.

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Decreased drug permeability to gram-negative

Gram-negative bacteria have more complex cell walls, like porins and efflux pumps, hindering drug penetration.

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Penicillin V absorption

Only a fraction (about one-third) of an oral penicillin V dose is absorbed due to its inability to survive stomach acid.

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Amoxicillin absorption

Amoxicillin is absorbed better compared to penicillin V due to its acid stability.

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PBPs (Penicillin Binding Proteins)

Bacterial enzymes responsible for cell wall synthesis.

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Altered PBPs and resistance

Modified PBPs in some bacteria have reduced affinity for beta-lactams. This explains some resistance, like in MRSA.

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Administration route considerations

The choice of administration route (oral, IV, IM) depends on the antibiotic's stability in acid and infection severity.

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Penicillin & Bone/CSF

Penicillin struggles to reach bone and cerebrospinal fluid (CSF) for treatment unless inflammation is present, making these sites difficult to target.

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Penicillin & Prostate Infections

Penicillin levels in the prostate are typically too low to effectively treat infections.

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Penicillin Metabolism

Penicillins are usually not significantly metabolized, except for penicillin G in patients with kidney issues. Nafcillin and oxacillin are primarily broken down in the liver.

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Penicillin Excretion

Penicillins are primarily eliminated via the kidneys, either through filtration or active transport.

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Probenecid & Penicillin

Probenecid increases blood levels of penicillin by competing for transport in the kidneys, delaying excretion.

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Penicillin Hypersensitivity

Penicillin allergy is common (about 10%), ranging from mild rashes to severe anaphylaxis. Cross-reactions can occur with other beta-lactam drugs.

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Penicillin & Diarrhea

Diarrhea is a frequent side effect of penicillin, potentially caused by Clostridium difficile (C. difficile) infection.

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Penicillin & Nephritis

Penicillins, particularly methicillin, can cause kidney inflammation (nephritis). Methicillin is no longer used clinically.

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First Generation Cephalosporins

These cephalosporins are like penicillin G but better at fighting staph bacteria that are resistant to regular penicillin. They have some activity against certain common gut bacteria, but not against all types of anaerobes.

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Second Generation Cephalosporins

These cephalosporins work better against a wider range of gram-negative bacteria than the first generation, but are less effective against gram-positive bacteria.

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Third Generation Cephalosporins

Important for treating infections, these cephalosporins are strong against gram-negative bacteria, especially those that make β-lactamases (enzymes that break down antibiotics). They include some medications commonly used in treatment of meningitis.

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Fourth Generation Cephalosporins

These cephalosporins are given by injection and are effective against a wide range of bacteria including staphylococci, streptococci (but only those that are susceptible to methicillin) and several gram-negative bacteria.

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Advanced Generation Cephalosporins

This type of cephalosporin (ceftaroline) is effective against MRSA (a type of bacteria resistant to many antibiotics), is used to treat certain skin and lung infections, and is effective against many types of bacteria.

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What is unique about ceftaroline?

Ceftaroline is the only β-lactam antibiotic in the US that is effective against MRSA. It is also broad-spectrum, meaning it is effective against many different types of bacteria.

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Why are there different generations of Cephalosporins?

Each generation of cephalosporins has been developed to be more effective against different types of bacteria and to overcome resistance mechanisms.

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What is a common side effect of third-generation cephalosporins?

Third-generation cephalosporins are associated with an increased risk of developing C. difficile infection (a serious intestinal infection).

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Carbapenems: CSF penetration

Carbapenems like imipenem, meropenem, and doripenem effectively cross the blood-brain barrier, reaching the cerebrospinal fluid (CSF) when the meninges are inflamed, making them useful for treating meningitis.

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Meropenem: CSF levels

Meropenem can achieve therapeutic levels in the CSF even without inflammation of the meninges, making it particularly effective against bacterial meningitis.

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Imipenem degradation

Imipenem is broken down by a dehydropeptidase enzyme in the kidney, limiting its effectiveness. To prevent this, it's combined with cilastatin.

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Monobactams: unique structure

Monobactams, like aztreonam, differ from other beta-lactams by having a single beta-lactam ring, not fused to another ring, targeting mainly gram-negative bacteria.

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Aztreonam: administration and toxicity

Aztreonam is administered intravenously or intramuscularly. It can accumulate in patients with kidney failure. While relatively safe, it can cause phlebitis, rash, and liver problems.

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β-lactamase inhibitors: function

These compounds, like clavulanic acid, sulbactam, and tazobactam, lack significant antibacterial activity alone. They inactivate β-lactamases, protecting other antibiotics like amoxicillin and ampicillin from destruction.

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Avibactam and vaborbactam: β-lactamase inhibitors

These newer β-lactamase inhibitors, unlike the traditional ones, lack the core β-lactam ring. They still effectively inactivate β-lactamases, safeguarding other antibiotics.

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β-Lactamase inhibitors: combination

β-Lactamase inhibitors are often combined with β-lactam antibiotics susceptible to β-lactamases, like amoxicillin, ampicillin, and piperacillin.

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Vancomycin Absorption

Vancomycin has poor absorption when taken orally. It is mainly used for infections in the colon, such as C. difficile infections.

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Lipoglycopeptides

Lipoglycopeptides (telavancin, oritavancin, dalbavancin) are a type of antibiotic that work against gram-positive bacteria. They are similar to vancomycin but more potent.

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Telavancin's Usage

Telavancin is an alternative to vancomycin for treating infections like skin and skin structure infections (ABSSSIs) or hospital-acquired pneumonia caused by resistant bacteria.

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Telavancin's Drawback

Telavancin can cause kidney problems (nephrotoxicity) and interact with medications that prolong the QT interval (like fluoroquinolones and macrolides).

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Oritavancin and Dalbavancin's Advantage

Oritavancin and dalbavancin have long half-lives (over 200 hours), which allows for single-dose treatment of ABSSSIs.

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Daptomycin's Key Feature

Daptomycin is a bactericidal lipopeptide antibiotic effective against resistant gram-positive bacteria, including MRSA and VRE.

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Daptomycin's Limitation

Daptomycin is inactivated by pulmonary surfactants, so it should not be used to treat pneumonia.

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Daptomycin's Dosage

Daptomycin is administered intravenously (IV) once daily.

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Study Notes

Cell Wall Inhibitors

  • Various classes of antibiotics inhibit bacterial cell wall synthesis

  • Penicillins:

    • Basic structure: core four-membered β-lactam ring, thiazolidine ring, and R side chain
    • Differ by the R substituent on the 6-aminopenicillanic acid residue
    • Side chain affects antimicrobial spectrum, stability to acid, cross-hypersensitivity, and susceptibility to β-lactamases

  • Cephalosporins:

    • Closely related to penicillins, both structurally and functionally
    • Mostly semisynthetic, chemically attaching side chains to 7-aminocephalosporanic acid
    • Structural changes on the acyl side chain alter antibacterial activity
    • More resistant than penicillins to some β-lactamases

  • Carbapenems:

    • Synthetic β-lactam antibiotics
    • Differing structure from penicillins: sulfur replaced by carbon in the thiazolidine ring
    • Examples: imipenem, meropenem, doripenem, ertapenem

  • Monobactams:

    • Disrupt bacterial cell wall synthesis
    • Unique: β-lactam ring not fused to another ring
    • Example: aztreonam

  • Other β-lactams:

    • Combinations exist (cephalosporin + β-lactamase inhibitor; carbapenem + β-lactamase inhibitor) to combat resistant bacteria or infections.
      • Examples: ceftolozane-tazobactam; ceftazidime-avibactam; meropenem-vaborbactam

  • Vancomycin:

    • Tricyclic glycopeptide
    • Active against aerobic and anaerobic gram-positive bacteria, including MRSA, MRSE, Enterococcus spp., and C. difficile
    • Binds to peptidoglycan precursors, disrupting polymerization and cross-linking, essential for cell wall integrity
    • Has a bactericidal effect
    • Used in skin and soft tissue infections, infective endocarditis, and nosocomial pneumonia

  • Lipoglycopeptides:

    • Telavancin, oritavancin, and dalbavancin
    • Bactericidal
    • Have a spectrum of similar activity against gram-positive bacteria
    • More potent than vancomycin
    • Inhibit bacterial cell wall synthesis, may also disrupt membrane potential

  • Daptomycin:

    • Cyclic lipopeptide antibiotic
    • Alternative for treating resistant gram-positive infections, including MRSA and VRE
    • Bactericidal, concentration-dependent
    • Used in complicated skin and skin structure infections, and bacteremia

  • Fosfomycin :

    • Synthetic antibacterial drug
    • Inhibits enolpyruvyl transferase, a key step in peptidoglycan synthesis
    • Active against E. coli and E. faecalis
    • First-line therapy for acute cystitis
    • Rapidly absorbed after oral administration
    • Excreted in the urine

  • Polymyxins:

    • Cationic polypeptides
    • Binds to phospholipids on gram-negative bacterial cell membranes, disrupting cell membrane integrity
    • Bactericidal agents, concentration dependent, used topically.
    • High risk of toxicity when used systemically

Resistance Mechanisms

  • β-Lactamase production, decreased permeability, and altered PBPs are common resistance mechanisms for these antibiotics

Pharmacokinetics

  • Administration routes depend on drug's stability to gastric acid and infection severity
  • Absorption, distribution, metabolism, excretion, and adverse reactions differ depending on specific drug class

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Cell Wall Inhibitors PDF

Description

This quiz explores various classes of antibiotics that inhibit bacterial cell wall synthesis, including penicillins, cephalosporins, carbapenems, and monobactams. It covers their structures, mechanisms, and how modifications to their structures influence their effectiveness. Test your understanding of these essential components in pharmacology!

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