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Ch. 13 - Viruses, Viroids, and Prions
Chapter 10, Problem 13.6a

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 the relationship between antibiotics and phage activation: Some antibiotics can induce the lytic cycle of bacteriophages, which are viruses that infect bacteria. This can lead to the expression of phage-encoded genes, including those for toxins.
Identify the role of Panton-Valentine leukocidin (PVL): PVL is a toxin produced by certain strains of Staphylococcus aureus, including MRSA (Methicillin-resistant Staphylococcus aureus). It is encoded by genes that can be carried on bacteriophages.
Consider the impact of antibiotic treatment on MRSA: When antibiotics are used to treat MRSA infections, they can sometimes trigger the activation of phage genes, leading to increased production of PVL.
Explain the consequences of increased PVL production: The release of PVL can damage white blood cells and tissues, leading to severe inflammatory responses and potentially life-threatening conditions.
Conclude with the risk of antibiotic-induced toxin release: Antibiotic treatment can inadvertently cause the release of phage-encoded toxins like PVL, exacerbating the infection and leading to severe disease.

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Key Concepts

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

Antibiotic Resistance and Gene Activation

Certain antibiotics can inadvertently activate bacterial phage genes, leading to the expression of virulence factors. This phenomenon occurs when antibiotics stress bacteria, triggering the activation of prophages that can enhance pathogenicity, such as toxin production.
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Panton-Valentine Leukocidin (PVL)

Panton-Valentine leukocidin is a potent toxin produced by some strains of Staphylococcus aureus, including MRSA. PVL targets and destroys immune cells, particularly neutrophils, leading to severe tissue damage and increased susceptibility to infections, especially after antibiotic treatment.

Impact of Antibiotics on Microbiota

Antibiotics can disrupt the normal microbiota, allowing opportunistic pathogens like MRSA to thrive. This disruption can lead to an imbalance in microbial populations, facilitating the overgrowth of harmful bacteria and the expression of virulence factors, resulting in severe infections.
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