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C H A P T E R 7 Pathogenesis

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  1. Handwashing is an important means of interrupting the chain

of transmission from one person to another. Infection by which

one of the following bacteria is most likely to be interrupted by

handwashing?

(A) Borrelia burgdorferi

(B) Legionella pneumophila

(C) Staphylococcus aureus

(D) Streptococcus agalactiae (group B streptococcus)

(E) Treponema pallidum

 

  1. Vertical transmission is the transmission of organisms from

mother to fetus or newborn child. Infection by which one of the

following bacteria is most likely to be transmitted vertically?

(A) Chlamydia trachomatis

(B) Clostridium tetani

(C) Haemophilus influenzae

(D) Shigella dysenteriae

(E) Streptococcus pneumonia

 

  1. The cells involved with pyogenic inflammation are mainly neutrophils,

whereas the cells involved with granulomatous inflammation

are mainly macrophages and helper T cells. Infection by

which one of the following bacteria is most likely to elicit granulomatous

inflammation?

(A) Escherichia coli

(B) Mycobacterium tuberculosis

(C) Neisseria gonorrhoeae

(D) Streptococcus pyogenes

(E) Staphylococcus aureus

 

  1. Which one of the following sets of properties of exotoxins and

endotoxins is correctly matched?

(A) Exotoxins—polypeptides; endotoxins—lipopolysaccharide

(B) Exotoxins—weakly antigenic; endotoxins—highly antigenic

(C) Exotoxins—produced only by gram-negative bacteria; endotoxins—

produced only by gram-positive bacteria

(D) Exotoxins—weakly toxic per microgram; endotoxins—highly

toxic per microgram

(E) Exotoxins—toxoid vaccines are ineffective; endotoxins—toxoid

vaccines are effective

 

  1. Which one of the following sets consists of bacteria both of which

produce exotoxins that increase cyclic AMP within human cells?

(A) Vibrio cholerae and Corynebacterium diphtheriae

(B) Clostridium perfringens and Streptococcus pyogenes

(C) Escherichia coli and Bordetella pertussis

(D) Corynebacterium diphtheriae and Staphylococcus aureus

(E) Bacillus anthracis and Staphylococcus epidermidis

 

  1. Which one of the following sets of bacteria produces exotoxins

that act by ADP-ribosylation?

(A) Corynebacterium diphtheriae and Escherichia coli

(B) Clostridium perfringens and Staphylococcus aureus

(C) Clostridium tetani and Bacillus anthracis

(D) Enterococcus faecalis and Mycobacterium tuberculosis

(E) Escherichia coli and Streptococcus pyogenes

 

  1. Which of the following bacteria produce an exotoxin that inhibits

the release of acetylcholine at the neuromuscular junction?

(A) Bacillus anthracis

(B) Bordetella pertussis

(C) Clostridium botulinum

(D) Corynebacterium diphtheriae

(E) Escherichia coli

 

  1. A 25-year-old man with abdominal pain was diagnosed with

acute appendicitis. He then had a sudden rise in temperature to

39C and a sudden fall in blood pressure. Which one of the following

is the most likely cause of the fever and hypotension?

(A) An exotoxin that ADP-ribosylates elongation factor-2

(B) An exotoxin that stimulates production of large amounts of

cyclic AMP

(C) An endotoxin that causes release of tumor necrosis factor

(D) An endotoxin that binds to class I MHC protein

(E) An exoenzyme that cleaves hyaluronic acid

 

  1. Several biotech companies have sponsored clinical trials of a

drug consisting of monoclonal antibody to lipid A. Sepsis caused

by which one of the following sets of bacteria is most likely to be

improved following administration of this antibody?

(A) Bordetella pertussis and Clostridium perfringens

(B) Escherichia coli and Neisseria meningitidis

(C) Pseudomonas aeruginosa and Bacillus anthracis

(D) Staphylococcus epidermidis and Staphylococcus aureus

(E) Streptococcus pneumoniae and Staphylococcus aureus

 

  1. Regarding endotoxin, which one of the following is the MOST

accurate?

(A) Endotoxin is a polypeptide, the toxic portion of which consists

of two d-alanines.

(B) Endotoxin is produced by both gram-positive cocci as well as

gram-negative cocci.

(C) Endotoxin acts by binding to class II MHC proteins and the

variable portion of the beta chain of the T-cell receptor.

(D) Endotoxin causes fever and hypotension by inducing the

release of interleukins such as interleukin-1 and tumor necrosis

factor.

(E) The antigenicity of endotoxin resides in its fatty acid side

chains.

✅ Answers (1)

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  1. (C)

Preventing Staph Infection

  1. Keep your hands clean by washing them thoroughly with soap and water. ...
  2. Keep cuts and scrapes clean and covered with bandages until they heal.
  3. Avoid contact with other people's wounds or bandages.
  4. Do not share personal items such as towels, clothing, or cosmetics.

 

 

 

  1. (A)

Chlamydia trachomatis colonisation is common in pregnant women, and it has been claimed that mother-to-child transmission may occur

 

 

  1. (B)

A granuloma is defined as an inflammatory mononuclear cell infiltrate that, while capable of limiting growth of Mycobacterium tuberculosis, also provides a survival niche from which the bacteria may disseminate. The tuberculosis lesion is highly dynamic and shaped by both, immune response elements and the pathogen.

 

 

  1. (A)

Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium. Endotoxins are heat stable lipopolysaccharide-protein complexes which form structural components of cell wall of Gram Negative Bacteria and liberated only on cell lysis or death of bacteria

 

 

  1. (C)

The toxin, present in all virulent strains of B. pertussis, is synthesized as a protoxin monomer that is cleaved into an active molecule, allowing it to enter a variety of eukaryotic cells. Once inside the cell, it is activated by calmodulin and catalyzes the production of large quantities of cyclic AMP.

 

 

  1. (A)

Bacterial ADP-ribosyltransferase toxins (bARTTs) are encoded by a range of bacterial pathogens, including human pathogens, such as Corynebacterium diphtheriae, Vibrio cholerae, Bordetella pertussis, Clostridium botulinum, and Streptococcus pyogenes, the plant pathogen Pseudomonas syringae

 

 

  1. (C)

Botulinum toxin (Botox) is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction and thus causes flaccid paralysis. Infection with the bacterium causes the disease botulism.

 

 

  1. (C)

 

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine that becomes elevated in chronic inflammatory states such as hypertension and diabetes and has been found to mediate both increases and decreases in blood pressure. High levels of TNF-α decrease blood pressure, whereas moderate increases in TNF-α have been associated with increased NaCl retention and hypertension.

 

 

  1. (B)

Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane

 

 

  1. (D)

Effects of endotoxin

Endotoxin interacts with cells and molecules of inflammation, immunity and haemostasis.

  • Fever is induced by interleukin-1, produced by the liver in response to endotoxin, acting on the temperature-regulating hypothalamus.
  • The action of lipopolysaccharide on platelets and activation of Hageman's factor causes disseminated intravascular coagulation with ensuing ischaemic tissue damage to various organs.
  • Septic shock occurs during severe infections with Gram-negative organisms when bacteria or lipopolysaccharide enter the bloodstream
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Answered on June 24, 2020 4:58 pm
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