Chapter 1.2 Cell Structures, Virulence Factors And Toxins Flashcards
What is the virulence of an organism?
Degree of organism pathogenicity
What does virulence depend on?
Presence of certain cell structures and on bacterial exotoxins and endotoxins (which are all virulence factors)
What are the 2 tests used by doctors or visualize capsules under a microscope to help identify bacteria?
India ink stain and Quellung Reation
What is the India Ink Stain?
This stain is not taken up by the capsule and the capsule appears as a transparent halo around the cell
What fungus uses primarily the India ink stain?
Crytococcus
What is the Quellung reaction?
When bacteria are mixed with antibodies that bind to the capsule causing the capsule to swell with water
How does the vaccine for Stretococcus pneumoniae work?
The vaccine contains antigens from the 23 most common capsules
A immune response is elicited against the capsular antigens
Production of antibodies that protects the individual against future infections of this organism
What are endospores?
Metabolically dormant forms of bacteria that are resistant to heat, cold, drying, and chemical agents
What are the 2 genera of bacteria that have endospores?
2 gram-positive bacteria: aerobic Bacillus and the anaerobic Clostridium
What is a plasmid?
Small adjacent circles of double-stranded DNA
*are often antibiotic resistant
What is special about bacteria that have endospores?
They are safe from antibodies and other immune defenses
When do spores form?
When there is a shortage of needed nutrients and can lie dormant for years
What is the mechanism of a facultative intracellular organism?
Inhibit phagosome-lysosomes fusion and escape the hydrogen peroxide and superoxide radials
What are exotoxins?
Proteins released by both gram-negative and gram-positive bacteria
What gram-positive bacteria does NOT release exotoxins?
Listeria monocytogenes (induces endotoxin instead)
What are 2 examples of gram-negative cells that secrete exotoxins?
Vibrio cholera
E. Coli
What diseases can be caused by bacterial exotoxins?
Anthrax, botulinum, tetanus, and cholera
What are enterotoxins?
Exotoxins that act on the GI tract to cause diarrhea
What is the end mechanism of enterotoxins?
Osmotic pull of fluid into the intestine which causes diarrhea
What disease manifestations are caused by enterotoxins?
Infectious diarrhea and food poisoning
How does infectious diarrhea occur by enterotoxins?
Bacteria colonize and bind to GI tract and continually release enterotoxins
Diarrhea will continue until the bacteria are destroyed by immune system or antibiotics
What are examples of bacteria that cause infectious diarrhea?
Vibrio cholera, E. Coli, Campylobacter jejuni, and Shigella dysenteriae
How does food poisoning occur by enterotoxins?
Bacteria grow in food and release enterotoxins in the food
The enterotoxin is ingested resulting in diarrhea and vomiting for less than 24 hours
What are examples of bacteria that cause food poisoning?
Bacillus cereus
Staphylococcus aureus
What are pyrogenic exotoxins?
Exotoxins that stimulate the release of cytokines
What are the manifestations from a pyrogenic exotoxin?
Rash, fever, toxic shock syndrome
What are examples bacteria that release of pyrogenic exotoxins?
Staphylococcus aureus and Streptococcus pyogenes
What are tissue invasive exotoxins?
Exotoxins that allow bacteria to destroy and tunnel through tissues
How does endotoxin differ from exotoxin?
Endotoxin is not a protein exerted from cells but a normal part of the outer membrane that sheds off, especially during lysis
What bacteria is endotoxin present in?
ONLY gram-negative bacteria with one exception: Listeria monocytogenes
*Listeria monocytogenes is the only gram-positive bacteria that has endotoxin
What is septic shock?
Deadly response to gram-positive and gram-negative infections
What is bacteremia?
Bacteria in the blood-stream and can be detected in blood culture
Can trigger immune system and result in sepsis and possibly death
What is sepsis?
Bacteremia that a uses a systemic immune response to the infection
What can be the symptoms of sepsis?
High or low temperature, elevation of the white blood cell count, fast heart rate or breathing rate.
What are the symptoms of septic shock?
Dangerous drop in blood pressure and organ dysfunction
What is the most famous endogenous mediator of sepsis?
TNF (also called cachectin)
What does TNF do during sepsis?
Triggers releases of IL-1 from macrophages and endothelial cells
What do the mediators cause during sepsis?
Vasodilation, hypotension, and organ system dysfunction
Where is the most common site for bacteria?
Respiratory system
What is the most common bacteria in the lung?
Pneumonia
What is the “fire early and hit everything” concept?
If a patient looks like they are going into septic shock- give them all the antibiotics to try and fight everything
*make sure to culture before giving them antibiotics because after you won’t have any to culture
What is used to block inflammation during septic shock?
TNF, IL-1, and anti-inflammatory agents (ibuprofen and steroids)
