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Ch. 15 - Antimicrobial Drugs
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
All textbooksNorman-McKay 2nd EditionCh. 15 - Antimicrobial DrugsProblem 10
Chapter 15, Problem 10

Assume a bacterium makes beta-lactamase. Could you still use a glycopeptide drug to treat an infection caused by this bacterium? Explain your reasoning.

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Understand the mechanism of beta-lactamase: Beta-lactamase is an enzyme produced by some bacteria that breaks down beta-lactam antibiotics (such as penicillins and cephalosporins) by hydrolyzing the beta-lactam ring, rendering these drugs ineffective.
Identify the class of glycopeptide drugs: Glycopeptides, such as vancomycin, inhibit bacterial cell wall synthesis but do so by a different mechanism than beta-lactam antibiotics. They bind to the D-Ala-D-Ala terminus of peptidoglycan precursors, preventing cell wall cross-linking.
Compare the target sites and resistance mechanisms: Since beta-lactamase specifically targets the beta-lactam ring structure, it does not affect glycopeptides, which lack this structure and have a different binding target.
Conclude on the effectiveness of glycopeptides: Because glycopeptides are not substrates for beta-lactamase, they remain effective against bacteria producing beta-lactamase, assuming no other resistance mechanisms are present.
Summarize the treatment implication: Therefore, if a bacterium produces beta-lactamase and is resistant to beta-lactam antibiotics, glycopeptide drugs can still be used as an alternative treatment option.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Beta-lactamase Enzyme

Beta-lactamase is an enzyme produced by some bacteria that breaks down beta-lactam antibiotics, such as penicillins and cephalosporins, rendering them ineffective. This enzyme specifically targets the beta-lactam ring, a crucial structure in these antibiotics, leading to antibiotic resistance.
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Enzymes

Mechanism of Action of Glycopeptide Antibiotics

Glycopeptide antibiotics, like vancomycin, inhibit bacterial cell wall synthesis by binding to the D-Ala-D-Ala terminus of peptidoglycan precursors. Unlike beta-lactams, glycopeptides do not contain a beta-lactam ring and are not affected by beta-lactamase enzymes.
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Introduction to Avoiding Host Defense Mechanisms

Antibiotic Resistance and Treatment Selection

When bacteria produce beta-lactamase, beta-lactam antibiotics become ineffective, so alternative drugs with different targets or structures are used. Since glycopeptides are structurally distinct and unaffected by beta-lactamase, they can be effective treatments against beta-lactamase-producing bacteria.
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Related Practice
Textbook Question

Which of the following antimicrobial properties would be the most crucial to consider in developing a new antimicrobial?

a. Selective toxicity

b. Ease of administration

c. Lack of drug interactions

d. Long half-life

e. The drug’s capacity to be bactericidal

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Textbook Question

Acquired antibiotic resistance can include all of the following except:

a. Altering an enzyme that a given drug may target

b. Making endospores

c. Altering a point of entry for a drug

d. Making enzymes that inactivate a drug

e. Increasing the number of efflux pumps that are active in a cell

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Textbook Question

Choose the true statement(s) about therapeutic index (TI). Select all that apply.

a. A drug with a high therapeutic index would be effective above the dose at which it is potentially toxic.

b. A narrow TI is preferable.

c. A drug for which the maximum safe dose is close to the minimum effective dose would have a high TI.

d. It is one measure of a drug’s general safety.

e. A drug that is not selectively toxic would most likely have a high TI.

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Textbook Question

The difference between a synthetic drug and a semisynthetic drug is that

a. the semisynthetic drug is a modified synthetic drug.

b. the synthetic drug is a modified natural drug.

c. the synthetic drug is a modified semisynthetic drug.

d. the semisynthetic drug is a modified natural drug.

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Textbook Question

If a gene encoding a bacterial transpeptidase enzyme undergoes mutation, which of the following antimicrobials may no longer be effective against the mutated bacterium?

a. Macrolides

b. Polypeptide drugs

c. Tetracyclines

d. Penicillins

e. Quinolones

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Textbook Question

Assume a clinical sample yields a strain of S. aureus containing a plasmid that encodes two antimicrobial-resistance genes. How did the bacterium most likely acquire these new resistance genes?

a. The strain was intrinsically resistant.

b. The strain obtained the genes through horizontal gene transfer.

c. The strain acquired the genes by a random mutation.

d. The strain picked up the genes by an efflux pump.

e. The strain acquired the genes through cell division events.

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