Bacteremia and Transformation in Microbiology
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Questions and Answers

What is the primary route by which pneumococci from the nasopharynx enter the lungs?

  • Through direct contact with the lungs
  • Through the bloodstream
  • Through the lymphatics
  • Through aspiration (correct)

    • What is the term for the process by which bacteria can spread widely in the body and reach tissues particularly suitable for their multiplication?

  • Transformation
  • Bacteremia (correct)
  • Conjugation
  • Transduction

    • What type of DNA is capable of recognizing and binding DNA from another organism?

  • Plasmid DNA
  • Genomic DNA
  • Extrachromosomal DNA (correct)
  • Chromosomal DNA

    • What is the term for highly mobile segments of DNA that can move from one part of the DNA to another?

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

    What is the result of recombination between extrachromosomal DNA and the chromosome?

    <p>Illegitimate or nonhomologous recombination</p> Signup and view all the answers

    What is the role of plasmids in bacterial virulence?

    <p>They encode many bacterial virulence factors</p> Signup and view all the answers

    What is the term for the process by which DNA from one organism is taken up by a different organism that is capable of recognizing and binding DNA?

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

    What is the term for bacterial viruses that can carry genes encoding virulence factors?

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

    What is the purpose of M protein in Streptococcus pyogenes?

    <p>To inhibit phagocytosis</p> Signup and view all the answers

    What type of cells are commonly used to study bacterial invasion in vitro?

    <p>HeLa cells</p> Signup and view all the answers

    What is the role of fibronectin in the adherence of Streptococcus pyogenes to buccal epithelial cells?

    <p>It acts as a receptor molecule for the bacteria</p> Signup and view all the answers

    What are the hairlike appendages on the surface of Streptococcus pyogenes?

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

    What is the result of Shigella species adhering to HeLa cells?

    <p>The formation of pseudopods by the HeLa cells</p> Signup and view all the answers

    What is the role of lipoteichoic acid in Streptococcus pyogenes?

    <p>It causes adherence of streptococci to buccal epithelial cells</p> Signup and view all the answers

    What is the genetic material responsible for the invasion of host cells by Shigella species?

    <p>A large plasmid</p> Signup and view all the answers

    What is the outcome of the invasion of host cells by Shigella species?

    <p>Engulfment of the bacteria by the host cell</p> Signup and view all the answers

    What is the effect of Theta toxin on cell membranes?

    <p>Splitting lecithin to phosphorylcholine and diglyceride</p> Signup and view all the answers

    What is the function of Fragment B of the diphtheria toxin?

    <p>Binding to specific host cell receptors</p> Signup and view all the answers

    What is the result of Diphtheria toxin inhibiting peptide chain elongation?

    <p>Disruption of normal cellular physiological functions</p> Signup and view all the answers

    What is the mode of action of TSST-1?

    <p>Binding to MHC-II and T-cell receptors</p> Signup and view all the answers

    What is the source of Clostridium tetani?

    <p>Contaminated wounds</p> Signup and view all the answers

    What is the characteristic of superantigens?

    <p>They stimulate T-cells by binding directly to MHC-II and T-cell receptors</p> Signup and view all the answers

    What is the effect of TSST-1 on organ systems?

    <p>Affects multiple organ systems</p> Signup and view all the answers

    What is the diagnosis associated with TSST-1?

    <p>Toxic shock syndrome</p> Signup and view all the answers

    What is the primary treatment for secondary fluid loss and acid–base imbalance in staphylococcal food poisoning?

    <p>Electrolyte and fluid replacement</p> Signup and view all the answers

    What is the result of LPS enhancement of glycolysis in many cell types?

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

    What is the typical timing of food preparation that leads to staphylococcal food poisoning?

    <p>Recently prepared but not properly refrigerated</p> Signup and view all the answers

    What is the effect of LPS on vascular permeability?

    <p>Increased vascular permeability</p> Signup and view all the answers

    What is the result of widespread arterio- and venular constriction in Gram-negative bacteremia?

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

    What is the mechanism of action of staphylococcal enterotoxin in the gut?

    <p>Stimulation of vagus nerve receptors</p> Signup and view all the answers

    What is the effect of DIC on vascular changes in Gram-negative bacteremia?

    <p>Contributes to vascular changes</p> Signup and view all the answers

    What is the characteristic of vomiting in staphylococcal food poisoning?

    <p>Frequent and projectile</p> Signup and view all the answers

    What is the name of the system used by Yersinia species to block phagocytosis and induce apoptosis?

    <p>Ysc-Yop system</p> Signup and view all the answers

    Which type of secretion system is contact-dependent and Sec-independent?

    <p>Type 3 secretion system</p> Signup and view all the answers

    What is the name of the toxin produced by P.aeruginosa?

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

    Which bacterium uses the Ysc-Yop system to control host cell signaling, invasion, and death?

    <p>Shigella species</p> Signup and view all the answers

    What is the name of the system used by E.coli to disrupt epithelial barriers and tight junctions?

    <p>Enteropathogenic system</p> Signup and view all the answers

    Which type of secretion system is used by N.gonorrhoeae for DNA export?

    <p>Type 4 secretion system</p> Signup and view all the answers

    What is the name of the toxin produced by H.pylori?

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

    Which bacterium uses the Type 5 secretion system?

    <p>N.</p> Signup and view all the answers

    Study Notes

    Bacteremia and Infection

    • Bacteremia allows bacteria to spread widely in the body and permits them to reach tissues suitable for their multiplication
    • Pneumococcal pneumonia is an example of the infectious process
      • S. pneumoniae can be cultured from the nasopharynx of 5-40% of healthy people
      • Infection develops in the terminal air spaces of the lungs in persons who do not have protective antibodies against that particular pneumococcal capsular polysaccharide type
      • Multiplication of the pneumococci and resultant inflammation lead to pneumonia

    Transformation and Genetic Elements

    • Transformation occurs when DNA from one organism is released into the environment and is taken up by a different organism that is capable of recognizing and binding DNA
    • Genes that encode many bacterial virulence factors are carried on plasmids, transposons, or phages
    • Plasmids are extrachromosomal pieces of DNA that can replicate
    • Transposons are highly mobile segments of DNA that can move from one part of the DNA to another
    • Bacterial viruses or phages are another type of mobile genetic element

    Adherence Mechanisms

    • Bacteria have evolved diverse mechanisms to promote adherence to host cells
    • Group A streptococci (Streptococcus pyogenes) have hairlike appendages called fimbriae that extend from the cell surface
    • Lipoteichoic acid, protein F, and M protein are found on the fimbriae
      • Lipoteichoic acid and protein F cause adherence of the streptococci to buccal epithelial cells
      • M protein acts as an antiphagocytic molecule and is a major virulence factor
    • Shigella species adhere to host cells in vitro, causing actin polymerization and engulfment of the bacteria
    • Adherence and invasion are mediated at least in part by products of genes located on a large plasmid common to many shigellae

    Toxins and Virulence Factors

    • Diphtheria toxin is a potent inhibitor of protein synthesis
    • Theta toxin, produced by clostridiae, has a necrotizing effect on cell membranes
    • S. aureus produces enterotoxins while growing in meat, dairy products, or other foods
      • Enterotoxins are superantigens that stimulate most T-cells by binding directly to MHC-II and T-cell receptors
    • TSST-1, produced by S. aureus, is a superantigen that causes toxic shock syndrome
    • LPS enhances glycolysis in many cell types and can lead to hypoglycemia
    • LPS is among the many different agents that can activate the alternative pathway of the complement cascade

    Type III Secretion Systems

    • Type III secretion systems are used by many Gram-negative bacteria to deliver toxins and virulence factors directly into host cells
    • Examples of Type III secretion systems include:
      • Yersinia species: Ysc-Yop system; toxins that block phagocytosis and induce apoptosis
      • P. aeruginosa: Cytotoxin
      • Shigella species: Controls host cell signaling, invasion, and death
      • Salmonella enterica subspecies enterica: Effectors from Salmonella pathogenicity islands I and II (SPI1 and SPI2) promote attachment to and invasion of host cells
      • E. coli: Enterohemorrhagic (EHEC) and enteropathogenic (EPEC); disruption of epithelial barriers and tight junctions
      • V. parahaemolyticus: Direct cytotoxicity

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    Description

    Learn about the spread of bacteria in the body through bacteremia and the process of transformation in microbiology, including the role of plasmids, transposons, and bacteriophages.

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