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Questions and Answers
What is the primary advantage of anti-staphylococcus penicillins?
What is the primary advantage of anti-staphylococcus penicillins?
Which combination is used to enhance the effectiveness of amoxicillin?
Which combination is used to enhance the effectiveness of amoxicillin?
Which of the following anti-staphylococcus penicillins has been withdrawn from use due to MRSA?
Which of the following anti-staphylococcus penicillins has been withdrawn from use due to MRSA?
What defines anti-pseudomonal penicillins?
What defines anti-pseudomonal penicillins?
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What is the role of clavulanate when used with amoxicillin?
What is the role of clavulanate when used with amoxicillin?
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What is the primary mechanism by which β-lactamases confer resistance to bacteria?
What is the primary mechanism by which β-lactamases confer resistance to bacteria?
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How can plasmid-encoded β-lactam resistance be spread among bacterial strains?
How can plasmid-encoded β-lactam resistance be spread among bacterial strains?
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What role do penicillin binding proteins (PBPs) play in bacterial resistance to β-lactams?
What role do penicillin binding proteins (PBPs) play in bacterial resistance to β-lactams?
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Which amino acid is specifically mentioned as being crucial for the binding of β-lactams to PBPs?
Which amino acid is specifically mentioned as being crucial for the binding of β-lactams to PBPs?
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What is a PBP mutation and how does it lead to antibiotic resistance?
What is a PBP mutation and how does it lead to antibiotic resistance?
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Which class of antibiotics is primarily affected by β-lactamases?
Which class of antibiotics is primarily affected by β-lactamases?
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What happens when a bacterial PBP mutates to have a lower affinity for a β-lactam antibiotic?
What happens when a bacterial PBP mutates to have a lower affinity for a β-lactam antibiotic?
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How many different classes of β-lactamases have been characterized according to the content?
How many different classes of β-lactamases have been characterized according to the content?
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What is a potential side effect of excessive vancomycin infusion?
What is a potential side effect of excessive vancomycin infusion?
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How does resistance to vancomycin occur in bacteria?
How does resistance to vancomycin occur in bacteria?
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Which bacteria serves as a reservoir for antibiotic resistance traits due to cephalosporin and vancomycin use?
Which bacteria serves as a reservoir for antibiotic resistance traits due to cephalosporin and vancomycin use?
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What is a major concern regarding vancomycin-resistant Enterococcus faecalis?
What is a major concern regarding vancomycin-resistant Enterococcus faecalis?
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What can help narrow the chances of antibiotic resistance spreading?
What can help narrow the chances of antibiotic resistance spreading?
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What structural feature is common to all penicillins?
What structural feature is common to all penicillins?
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How do β-lactam antibiotics inhibit bacterial growth?
How do β-lactam antibiotics inhibit bacterial growth?
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What is a major reason for the rapid development of bacterial resistance to penicillin?
What is a major reason for the rapid development of bacterial resistance to penicillin?
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Which component of bacterial cells is primarily affected by penicillins?
Which component of bacterial cells is primarily affected by penicillins?
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What is a consequence of the β-lactam ring's structural instability?
What is a consequence of the β-lactam ring's structural instability?
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In what year was penicillin first clinically trialed in humans?
In what year was penicillin first clinically trialed in humans?
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What causes bacterial cells to burst when treated with β-lactams?
What causes bacterial cells to burst when treated with β-lactams?
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Which statement is true regarding bacterial β-lactamase enzymes?
Which statement is true regarding bacterial β-lactamase enzymes?
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Which of the following is a characteristic of cefepime?
Which of the following is a characteristic of cefepime?
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What should be done for patients with renal dysfunction when administering cephalosporins?
What should be done for patients with renal dysfunction when administering cephalosporins?
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Which organisms are effectively targeted by cefepime?
Which organisms are effectively targeted by cefepime?
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In which situation should cephalosporins be avoided?
In which situation should cephalosporins be avoided?
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What is a common adverse drug effect (ADE) associated with cephalosporins?
What is a common adverse drug effect (ADE) associated with cephalosporins?
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What is the reason for the reduced effectiveness of cephalosporins against certain bacteria?
What is the reason for the reduced effectiveness of cephalosporins against certain bacteria?
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What distinguishes carbapenems from other β-lactams?
What distinguishes carbapenems from other β-lactams?
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Which statement about cefazolin is correct?
Which statement about cefazolin is correct?
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Study Notes
Penicillin Discovery and Properties
- Alexander Fleming discovered penicillin by observing clear zones of inhibition around a fungal colony in a bacterial culture.
- Penicillin was purified and trialed clinically in humans in 1943.
- Penicillin is a β-lactam antibiotic that inhibits bacterial cell wall synthesis by forming a covalent bond with the bacterial transpeptidase enzyme, inactivating it and preventing cross-linking.
- Penicillins are prone to degradation by bacterial β-lactamase enzymes.
Bacterial Resistance to Penicillin
- Bacterial resistance to penicillin arose within 15 years of its clinical use.
- Resistance develops via spontaneous random mutation, with resistant strains having a selective growth advantage over susceptible ones.
- β-lactamase enzymes, encoded by genes within bacterial plasmids, can be spread between strains through conjugation.
- β-lactamases hydrolyze the β-lactam ring, rendering the antibiotic ineffective.
- Bacteria can also mutate their own penicillin-binding protein (PBP), changing its affinity for the antibiotic.
Modified Penicillins to Overcome Resistance
- Modified penicillins, like flucloxacillin, dicloxacillin, and oxacillin, were designed to resist β-lactamase degradation.
- Methicillin, another β-lactamase-resistant penicillin, has been withdrawn due to the emergence of MRSA.
- MRSA strains are resistant to flucloxacillin, dicloxacillin, and oxacillin.
Broad Spectrum Penicillins and Combinations
- Amoxicillin and ampicillin are broad-spectrum penicillins.
- Amoxicillin can be combined with a β-lactamase inhibitor, clavulanic acid, to form Augmentin, which increases its effectiveness against β-lactamase producing bacteria.
Anti-pseudomonal Penicillins
- Piperacillin and ticarcillin are anti-pseudomonal penicillins with a wide spectrum of activity, especially effective against Pseudomonas aeruginosa infections.
- Piperacillin is often combined with tazobactam, and ticarcillin with clavulanic acid, to overcome β-lactamase resistance.
Cephalosporins
- Cephalosporins are a class of β-lactam antibiotics with a similar mechanism of action to penicillin.
- They are generally well tolerated but can cause allergic reactions.
- They are divided into generations, with newer generations having broader spectrum activity.
- Resistance to cephalosporins can arise through the production of extended-spectrum β-lactamases (ESBLs).
- Cephalosporins can be administered intravenously or intramuscularly due to poor oral absorption.
Carbapenams
- Carbapenams are synthetic β-lactam antibiotics with a wide spectrum of activity
- They are effective against many β-lactamase-producing bacteria.
- They can be used orally to treat severe antibiotic-associated C. difficile colitis infections.
Vancomycin
- Vancomycin is a glycopeptide antibiotic that inhibits cell wall synthesis by binding to the terminal D-Ala-D-Ala residues of peptidoglycan precursors.
- It is effective against Gram-positive bacteria, especially those resistant to other antibiotics.
- Vancomycin resistance can arise by bacterial production of a new pentapeptide that ends in D-Ala-D-Lac, which does not bind vancomycin.
- Vancomycin-resistant Enterococci (VRE) are a significant concern.
Enterococcus faecalis and Antibiotic Resistance
- Widespread use of antibiotics such as cephalosporins and vancomycin has led to the proliferation of E. faecalis.
- E. faecalis has developed resistance to vancomycin and can transfer these resistance genes to other pathogens like S. aureus.
- This makes it a significant reservoir of antibiotic-resistance traits.
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Description
Explore the groundbreaking discovery of penicillin by Alexander Fleming and its properties as an antibiotic. Learn about the significant issue of bacterial resistance that emerged shortly after its introduction and the mechanisms by which bacteria develop resistance.