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Microbial Infection and Pathogenesis - Cytolytic and Superantigen Exotoxins

6 important questions on Microbial Infection and Pathogenesis - Cytolytic and Superantigen Exotoxins

What are the differences between the terms "exotoxins" and "cytotoxins?"

Exotoxins are toxins released by certain bacteria as part of their growth, while cytotoxins are toxic substances that specifically target and damage cells. Exotoxins are usually secreted by bacteria into their environment, whereas cytotoxins can include various types of substances, even those produced by the body's own cells. Both exotoxins and cytotoxins can have harmful effects on the body's cells and tissues.

Define cytolytic exotoxins and provide an example of their action. How are hemolysins related to cytolytic exotoxins?

Cytolytic exotoxins, or cytotoxins, are soluble proteins that damage the host cytoplasmic membrane, leading to cell lysis. An example is the a-toxin of Clostridium perfringens, which acts as a lecithinase to dissolve membrane lipids. Hemolysins are often called cytolytic exotoxins because they cause cell lysis, particularly in red blood cells.

Explain the mode of action of Staphylococcal a-toxin. How does it lead to cell lysis, and what is the significance of its activity in the context of gas gangrene?

Staphylococcal a-toxin forms nonlytic heptamers associated with the host cell membrane, creating pores that release cytoplasmic contents and allow the influx of extracellular materials. This activity leads to cell lysis. In gas gangrene caused by Clostridium perfringens, the lecithinase activity of the a-toxin helps destroy tissues and release proteins for bacterial metabolism.
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What is toxic shock syndrome (TSS), and how is it associated with superantigen exotoxins? Provide examples of bacteria that produce superantigen exotoxins causing TSS.

TSS is a severe condition triggered by exposure to superantigen exotoxins, leading to a systemic immune response with symptoms like hypotension, organ failure, and systemic shock. Staphylococcus aureus and Streptococcus pyogenes are examples of bacteria causing TSS through the secretion of superantigen exotoxins.

Describe the symptoms and clinical diagnosis of toxic shock syndrome (TSS). In what situations might TSS be more life-threatening?

Symptoms of TSS include fever of 39°C or greater, low blood pressure (systolic < 90 mm Hg), and functional disruption of three or more organ systems, often gastrointestinal, kidney, and liver. TSS can be more life-threatening in individuals with weakened immune systems due to cancer, drug treatments, HIV infection, or old age.

Compare and contrast the mechanisms of action between cytolytic exotoxins and superantigen exotoxins. Provide examples of each and explain their roles in pathogenesis.

Cytolytic exotoxins, like hemolysins, damage host cytoplasmic membranes, causing cell lysis. Staphylococcal a-toxin is an example. Superantigen exotoxins, such as those from Staphylococcus aureus and Streptococcus pyogenes, trigger a massive immune response, leading to systemic effects like TSS.

The question on the page originate from the summary of the following study material:

Brock Biology of Microorganisms, Global Edition | 9781292235103 | Michael T Madigan, et al

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