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Questions and Answers
What is the primary route by which pneumococci from the nasopharynx enter the lungs?
What is the term for the process by which bacteria can spread widely in the body and reach tissues particularly suitable for their multiplication?
What type of DNA is capable of recognizing and binding DNA from another organism?
What is the term for highly mobile segments of DNA that can move from one part of the DNA to another?
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What is the result of recombination between extrachromosomal DNA and the chromosome?
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What is the role of plasmids in bacterial virulence?
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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?
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What is the term for bacterial viruses that can carry genes encoding virulence factors?
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What is the purpose of M protein in Streptococcus pyogenes?
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What type of cells are commonly used to study bacterial invasion in vitro?
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What is the role of fibronectin in the adherence of Streptococcus pyogenes to buccal epithelial cells?
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What are the hairlike appendages on the surface of Streptococcus pyogenes?
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What is the result of Shigella species adhering to HeLa cells?
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What is the role of lipoteichoic acid in Streptococcus pyogenes?
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What is the genetic material responsible for the invasion of host cells by Shigella species?
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What is the outcome of the invasion of host cells by Shigella species?
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What is the effect of Theta toxin on cell membranes?
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What is the function of Fragment B of the diphtheria toxin?
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What is the result of Diphtheria toxin inhibiting peptide chain elongation?
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What is the mode of action of TSST-1?
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What is the source of Clostridium tetani?
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What is the characteristic of superantigens?
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What is the effect of TSST-1 on organ systems?
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What is the diagnosis associated with TSST-1?
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What is the primary treatment for secondary fluid loss and acid–base imbalance in staphylococcal food poisoning?
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What is the result of LPS enhancement of glycolysis in many cell types?
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What is the typical timing of food preparation that leads to staphylococcal food poisoning?
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What is the effect of LPS on vascular permeability?
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What is the result of widespread arterio- and venular constriction in Gram-negative bacteremia?
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What is the mechanism of action of staphylococcal enterotoxin in the gut?
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What is the effect of DIC on vascular changes in Gram-negative bacteremia?
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What is the characteristic of vomiting in staphylococcal food poisoning?
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What is the name of the system used by Yersinia species to block phagocytosis and induce apoptosis?
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Which type of secretion system is contact-dependent and Sec-independent?
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What is the name of the toxin produced by P.aeruginosa?
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Which bacterium uses the Ysc-Yop system to control host cell signaling, invasion, and death?
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What is the name of the system used by E.coli to disrupt epithelial barriers and tight junctions?
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Which type of secretion system is used by N.gonorrhoeae for DNA export?
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What is the name of the toxin produced by H.pylori?
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Which bacterium uses the Type 5 secretion system?
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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.
