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Ch. 13 - Viruses, Viroids, and Prions
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 13 - Viruses, Viroids, and PrionsProblem 6
Chapter 13, Problem 6

Some antibiotics activate phage genes. MRSA releasing Panton-Valentine leukocidin is a toxin that can cause a life-threatening disease. Why can such a disease develop following antibiotic treatment?

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1
Understand that some antibiotics can induce the SOS response in bacteria, which is a stress response to DNA damage.
Recognize that the SOS response can activate prophages (dormant phage genes integrated into the bacterial genome) to enter the lytic cycle, leading to phage gene expression.
Know that in MRSA (Methicillin-resistant Staphylococcus aureus), the genes encoding Panton-Valentine leukocidin (PVL) are often carried on prophages.
Realize that antibiotic treatment can trigger prophage activation, causing increased production and release of PVL toxin.
Conclude that this increased toxin release can lead to severe tissue damage and life-threatening disease following antibiotic treatment.

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Key Concepts

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

Phage Activation by Antibiotics

Certain antibiotics can induce the SOS response in bacteria, triggering the activation of prophages—viral DNA integrated into the bacterial genome. This activation leads to phage gene expression, sometimes resulting in the production and release of toxins encoded by these phages.
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Bacteriophage: Filamentous Phage Infections

Panton-Valentine Leukocidin (PVL) Toxin

PVL is a cytotoxin produced by some strains of MRSA, encoded by genes often carried on bacteriophages. It targets and destroys white blood cells, leading to severe tissue damage and contributing to life-threatening infections such as necrotizing pneumonia.
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Introduction to Pathogenic Toxins

Impact of Antibiotic Treatment on MRSA Pathogenicity

Antibiotic treatment can unintentionally enhance MRSA virulence by inducing prophage activation, increasing PVL toxin production. This paradoxical effect can worsen disease severity despite bacterial killing, explaining why life-threatening conditions may develop after antibiotic use.
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Related Practice
Textbook Question

The ability of a virus to infect an organism is regulated by

a. the host species.

b. the type of cells.

c. the availability of an attachment site.

d. cell factors necessary for viral replication.

e. all of the above

Textbook Question

Compare biosynthesis of a + stranded RNA and a - stranded RNA virus.

Textbook Question

Recall from Chapter 1 that Koch's postulates are used to determine the etiology of a

disease. Why is it difficult to determine the etiology of

a. a viral infection, such as influenza?

b. cancer?

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Textbook Question

Label the principal events of attachment, biosynthesis, entry, and maturation of a + stranded RNA virus. Draw in uncoating.

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Textbook Question

An example of lysogeny in animals could be

a. slow viral infections.

b. latent viral infections.

c. T-even bacteriophages.

d. infections resulting in cell death.

e. none of the above

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Textbook Question

Which of the following statements is false?

a. Viruses contain DNA or RNA.

b. The nucleic acid of a virus is surrounded by a protein coat.

c. Viruses multiply inside living cells using viral mRNA, tRNA, and ribosomes.

d. Viruses cause the synthesis of specialized infectious elements.

e. Viruses multiply inside living cells.

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