40 Questions
What is the role of biofilm in E. coli's virulence factor and what is the consequence of this on the intestinal surface?
Biofilm facilitates E. coli's attachment to the intestinal surface, leading to rearrangement of actin, creation of pedestals, and subsequently, diarrhea due to impaired nutrient and water absorption.
How do microbes, such as E. coli, attach to the body surface?
Microbes attach to the body surface through specific interactions between proteins and oligosaccharides on their surface and the host cell's surface, including lipid bilayer and decorated proteins.
What is the role of selectins, such as P-selectin, in microbial attachment?
Selectins, like P-selectin, bind to sugars on proteins (e.g., iCAMs/LFAs) on the host cell surface, facilitating microbial attachment.
How do bacteria, such as E. coli, target host proteins for attachment?
Bacteria target host proteins that are frequently present and difficult to change, as they have evolved to do so.
What is the significance of oligosaccharides on microbial surface proteins?
Oligosaccharides on microbial surface proteins facilitate attachment to the host cell surface by binding to selectins and other host receptors.
What is the role of virulence factors, such as the one knocked out in the E. coli experiment, in microbial pathogenesis?
Virulence factors, such as the one knocked out in the E. coli experiment, contribute to microbial disease-causing mechanisms, including attachment, colonization, and infection.
What is the role of adhesins on fimbriae in Gonorrhoeae?
To attach to the host cell
How does Shigella infect host cells?
By inducing endocytosis
What is the role of Streptococcus mutans in oral biofilm formation?
To convert dietary sugar into acid, increasing the chance of cavity formation
What is one way that bacteria can evade the host's immune system?
By covering themselves with sugar
How do bacteria such as E. coli achieve antigenic variation?
Through rapid generation time and hypermutable regions
What is the role of the capsule in S. pneumoniae?
It is an essential virulence factor
What is the primary mechanism by which pathogens bind to host cells?
Adhesins or ligands bind to cell surface proteins.
What is the term for the infectious dose that causes symptoms in 50% of infected individuals?
ID 50
How do bacteria evade the host's immune system?
Through immunoevasion mechanisms, such as antigenic variation.
What is the purpose of bacterial proteases?
To break down host tissue and create a portal of entry.
What is the term for the toxicity of a pathogen that causes death in 50% of infected individuals?
LD 50
What is the role of exotoxins in bacterial pathogenesis?
Exotoxins can kill host cells, allowing the bacterium to use the host's resources.
What is the function of the B subunit in A-B subunit toxins?
To bind to the cell surface
What is the target of the Diphtheria toxin in the cell?
ADP ribosylation of EF-2
What is the mechanism of superantigen toxin action?
Bypassing the specificity of T cell receptors
What is the effect of the Diphtheria toxin on protein synthesis?
Inhibition of protein synthesis
What is the characteristic of superantigen toxins that distinguishes them from A-B subunit toxins?
They bypass the specificity of T cell receptors
What is the result of T cell overstimulation by superantigen toxins?
Immune system overstimulation
What happens when G- bacteria are killed by the immune system?
LPS is released into the bloodstream, triggering an inflammatory response
What is the term for the presence of G- negative toxin in the bloodstream?
Septicemia
What is the role of LPS binding protein in the inflammatory response?
It forms a complex with LPS and interacts with macrophages
What is the purpose of the Limulus amoebocyte lysate assay (LAL assay)?
To detect the presence of LPS in the bloodstream
What is the term for the severe inflammatory response triggered by LPS in the bloodstream?
Septic shock
What is the role of mobile gene elements, such as plasmids and transposons, in bacterial pathogenesis?
They carry toxin genes and antibiotic resistance
What is the characteristic of exotoxins?
They are secreted by bacteria and have specific targets.
Which of the following is an example of an exotoxin?
Hemolysin
What is the role of Antitoxin in relation to exotoxins?
It blocks the action of exotoxins
Which bacteria produce a lot of exotoxins?
Staphylococcus aureus and Streptococcus pyogenes
What is the characteristic of AB subunit toxins?
They have two subunits, one active and one binding
What is the role of superantigens in relation to exotoxins?
They are a type of exotoxin that causes the immune system to overreact
What is the mechanism of action of membrane disrupting toxins?
They create a channel in the membrane, allowing unregulated flow of ions
What is the characteristic of cytolysin?
It targets any cell in the body
How do bacteria, such as Staphylococcus aureus, protect themselves from the immune system?
They produce protein A, which binds to the Fc part of any antibody
What is the role of kinases in relation to Staphylococcus aureus?
They dissolve blood clots, allowing the bacteria to spread
This quiz covers the mechanisms of bacterial adhesion and evasion of host defenses, including the role of fimbriae, glycocalyx, and biofilms in bacterial attachment and colonization. Test your knowledge of the different bacterial species involved, such as E. coli, Shigella, and Streptococci.
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