22 Questions
What is the mechanism by which V. cholerae causes acute diarrhea?
Releasing a toxin that binds to ganglioside receptors on the surface of intestinal epithelium cells, triggering cAMP production and ion channel activation
What effect does the build-up of ions in the intestinal lumen have on the body?
It draws water from cells and tissues via osmosis, causing acute diarrhea
What is the appearance of diarrhea due to cholera?
Milky and pale, resembling water in which rice has been rinsed
What can severe dehydration due to cholera lead to if left untreated?
Coma and shock
What is the causal agent for cholera?
Vibrio cholerae
Which mechanism allows pathogens to attach to host cells?
Adherence
What causes post-streptococcal diseases like rheumatic fever and glomerulonephritis?
Immunological response
How do bacteriophages contribute to bacterial virulence?
Gene transfer
What is the distinction between intracellular and extracellular pathogens related to?
Gene transfer
How do pathogens enter the body?
Exposure
What can Streptococcus pyogenes cause?
Rheumatic fever
What is a sequela of pharyngitis or skin infections?
Post-streptococcal glomerulonephritis
What leads to acquisition of specific virulence attributes in bacteria?
Gene transfer
How do bacteriophages contribute to lysogenic conversion?
Gene transfer
What causes damage in post-streptococcal glomerulonephritis?
Antigen-antibody complexes
What do antibodies against M protein cross-react with in rheumatic fever?
Joint, heart, and brain tissue
Exotoxins are best described as:
Proteins released by pathogens targeting cells and tissues
Which type of exotoxin lyses host cells by creating protein channels in the plasma membrane?
Pore forming toxins
Which of the following is a main cause of septic shock?
Endotoxins
What is the leading cause of death in intensive care units with a mortality rate of 30-50%?
Septic shock
Which of the following is a characteristic of the biofilm mode of growth?
Increases virulence
What is used as a source of iron in bacterial iron acquisition?
Host transferrin and lactoferrin
Study Notes
- Exotoxins: proteins released by pathogens into the surroundings as they grow, specifically targeting cells and tissues.
- Endotoxins: structural component of Gram-negative bacterial cell walls (LPS) that can be toxic to specific hosts.
- Injected toxins: toxins directly injected into mammalian cells.
Exotoxins:
- AB exotoxins: composed of two subunits, A subunit responsible for toxic effect and B subunit binding to specific target cells.
- Membrane-disrupting toxins:
- Pore forming toxins: lyse host cells by creating protein channels in the plasma membrane.
- Leukocidins: kill leukocytes (neutrophils, T lymphocytes) and dendritic cells, contributing to innate and adaptive immune responses.
- Hemolysins: lyse red blood cells.
- Phospholipases: hydrolyze phospholipids and destroy local populations of white blood cells and red blood cells.
Endotoxins:
- Main cause of septic shock: characterized by fever, hypotension, and disseminated intravascular coagulation.
- Septic shock is leading cause of death in intensive care units with a mortality rate of 30-50%.
- Gram-negative bacteria produce endotoxins, primarily lipopolysaccharide, which can induce disease.
Injected toxins:
- Neutralized by specific antibodies.
- Potential vaccine candidates.
- Toxins injected into the cytoplasm cannot be neutralized.
- Toxin production and direct injection occur only upon bacteria contact with the target cell.
- Many human pathogens produce eukaryotic cell effectors/toxins.
Biofilm mode of growth:
- Physiologically different from planktonic growth.
- Can cause chronic infections.
- Increases virulence.
- Becomes less sensitive to antibiotics.
- Makes cells in the biofilm more resistant to host defense.
Bacterial iron acquisition:
- Uses siderophores, hemophores, and bacterioferritin.
- Host transferrin and lactoferrin are sources of iron.
- Free iron (Fe3+) is chelated by siderophores and hemophores.
- Iron is transported into the cell by receptors and heme-binding proteins.
- Stored iron (bacterioferritin) is used as an energy source.
Test your knowledge of the mechanisms behind cholera pathogenicity with this quiz. Learn about how Vibrio cholerae releases a toxin (AB) that binds to receptor cells on the intestinal epithelium, triggering specific cellular responses.
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