Microbiology: Toxins and Infections
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Questions and Answers

Endotoxins are also known as?

Lipid A

When would endotoxins be released from a bacterial cell?

When the cell dies

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

Fever

Why is a release of endotoxin into the bloodstream potentially deadly?

<p>It can lower blood pressure and cause the patient to go into shock</p> Signup and view all the answers

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)?

<p>cytotoxin</p> Signup and view all the answers

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

<p>B domain</p> Signup and view all the answers

How are superantigens different from other types of exotoxins?

<p>Superantigens cause an overstimulation of the host immune system</p> Signup and view all the answers

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)?

<p>superantigen</p> Signup and view all the answers

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)?

<p>neurotoxin</p> Signup and view all the answers

The most frequently used portal of entry for pathogens is the?

<p>mucous membranes of the respiratory tract</p> Signup and view all the answers

The ID50 is?

<p>the dose that will cause an infection in 50 percent of the test population</p> Signup and view all the answers

All of the following are examples of entry via the parenteral route EXCEPT?

<p>hair follicle</p> Signup and view all the answers

All of the following are used by bacteria to attach to host cells EXCEPT?

<p>A-B toxins</p> Signup and view all the answers

In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?

<p>False</p> Signup and view all the answers

Which of the following would be an example of an infection initiated via the parenteral route?

<p>An individual contracts hepatitis B from an accidental stick with a contaminated needle</p> Signup and view all the answers

Which of the following statements about adherence is true?

<p>False</p> Signup and view all the answers

In general, the LD50 for exotoxins is much greater than the LD50 for endotoxins.

<p>False</p> Signup and view all the answers

Biofilms provide pathogens with an adhesion mechanism and aid in resistance to antimicrobial agents.

<p>True</p> Signup and view all the answers

All of the following contribute to a pathogen's invasiveness EXCEPT?

<p>Toxins</p> Signup and view all the answers

Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?

<p>fibrinolysin</p> Signup and view all the answers

Endotoxins are?

<p>part of the gram-negative cell wall</p> Signup and view all the answers

Siderophores are bacterial proteins that compete with the host's?

<p>iron-transport proteins</p> Signup and view all the answers

Superantigens produce intense immune responses by stimulating lymphocytes to produce?

<p>cytokines</p> Signup and view all the answers

Which of the following contributes to the virulence of a pathogen?

<p>numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production</p> Signup and view all the answers

Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages?

<p>give new gene sequences to the host bacteria</p> Signup and view all the answers

Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to?

<p>superantigens</p> Signup and view all the answers

Endotoxins in sterile injectable drugs could cause?

<p>septic shock symptoms</p> Signup and view all the answers

In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?

<p>to ensure that a sterilized medical device is free of endotoxin</p> Signup and view all the answers

Which of the following statements about lysogenic conversion is true?

<p>False</p> Signup and view all the answers

In A-B exotoxins, the A component binds to the host cell receptor so that the B component can enter the cell.

<p>False</p> Signup and view all the answers

Cytopathic effects are changes in host cells due to?

<p>viral infections</p> Signup and view all the answers

Which of the following is NOT a cytopathic effect (CPE) of viruses?

<p>False</p> Signup and view all the answers

Study Notes

Endotoxins and Exotoxins

  • Endotoxins, also called Lipid A, are components of the gram-negative bacterial cell wall.
  • Release of endotoxins occurs when a bacterial cell dies, leading to potential septic shock by lowering blood pressure.
  • The first observable sign of endotoxin release is typically fever.
  • Cytotoxins are exotoxins that damage or kill host cells.
  • A-B toxins have a B domain that binds to host cell surface receptors.

Superantigens and Neurotoxins

  • Superantigens cause an excessive immune response, distinct from other exotoxins.
  • Exposure to superantigens can lead to rapid onset of high fever and unresponsiveness, indicative of intense immune reaction.
  • Neurotoxins are associated with bacterial infections causing uncontrollable muscle spasms.

Infection Pathways and LD50

  • The mucous membranes of the respiratory tract are the most common entry point for pathogens.
  • ID50 refers to the infectious dose that causes infection in 50% of the test population.
  • LD50 indicates the dose lethal to 50% of the test subjects; for instance, Shiga toxin is more lethal than staphylococcal enterotoxin.
  • Parenteral route infections, like hepatitis B from contaminated needles, bypass normal entry points.

Pathogen Adherence and Virulence Factors

  • Bacterial adhesins, primarily glycoproteins or lipoproteins, facilitate attachment to host cells.
  • Factors contributing to a pathogen's invasiveness include the number of microorganisms entering the host, evasion of host defenses, and toxin production.
  • Biofilms enhance pathogen adhesion and resistance to antimicrobial agents.

Bacterial Enzymes and Iron Competition

  • Fibrinolysin is an enzyme that aids in spreading bacteria like Streptococcus pyogenes by digesting blood clots.
  • Siderophores are proteins that help bacteria compete with host iron-transport proteins, essential for bacterial growth.

Immune Response and Cytopathic Effects

  • Superantigens trigger lymphocytes to produce cytokines, leading to intense immune responses.
  • Symptoms of inflammation and shock from gram-positive infections are often due to superantigens' actions.
  • Cytopathic effects (CPE) represent the changes in host cells during viral infections; all listed options can be CPEs.

Lysogenic Conversion and Endotoxin Testing

  • Lysogenic bacteriophages enhance bacterial virulence by transferring new gene sequences to host bacteria.
  • The Limulus amebocyte lysate (LAL) assay tests for endotoxins in sterile injectable drugs, crucial for preventing septic shock.
  • Exotoxin production is frequently a result of lysogenic infections, highlighting the importance of bacteriophages in pathogenicity.

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Explore the fascinating world of endotoxins, exotoxins, superantigens, and neurotoxins through this quiz. Learn about their impact on the immune system and infection pathways. Test your knowledge on key concepts such as LD50 and the entry points for pathogens.

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