Flashcards in Cell Structures - Virulence Factors And Toxins Deck (33):
What is the structure by which the flagellum is affixed to the bacteria?
By a basal body, which spans through the entire cell wall, binding to the inner and outer cell membrane in gram negative bacteria and to the inner membrane in gram-positive bugs (the gram-positive bacteria don't have an outer membrane).
What kinds of flagella can bacteria have?
1. Single polar flagellum : Vibrio cholera.
2. Many peritrichous flagella all around the cell : E.coli and Proteus mirabilis.
3. Periplasmic flagella : spirochetes.
Does shigella have flagella?
What are the Pili (also called fimbriae)?
1. Straight filaments arising from the bacterial cell wall, making the bacterium look like a porcupine.
2. They are much shorter than flagella and do not move.
3. Serve as adherence factors - adhesins.
Mention some bacteria that have pili and utilize them as adhesins.
1. Neisseria gonorrhea : pili that allow it to bind to cervical cells and buccal cells to cause gonorrhea.
2. E. coli + Campylobacter jejuni cannot cause diarrhea without their adhesins to bind to the intestinal epithelium.
3. Bordetella pertussis uses its adhesin to bind to ciliated respiratory cells and cause whooping cough.
What are the components of the bacterial capsule?
They are usually composed of simple sugar residues.
Bacteria secrete these sugar moieties, which then coat their outer wall.
What is unique about Bacillus anthracis' capsule?
It is made up of amino acid residues.
What is the main significance of a bacterial capsule?
Capsules enable bacteria to be more virulent because macrophages and neutrophils are unable to phagocytize the encapsulated buggers. (e.g. Streptococcus pneumoniae)
What are the two important tests that enable doctors to visualize capsules under the microscope and aid in identifying bacteria?
1. India ink stain : the capsule appears as a transparent halo around the cell. (used primarily to identify the fungus Cryptococcus)
2. Quelling reaction : bacteria are mixed with antibodies that bind to the capsule.
What contains a vaccine against streptococcus pneumoniae?
Antigens from the 23 most common types of capsules.
What are the two genera of bacteria that form endospores?
1. The aerobic Bacillus
2. The anaerobic Clostridium
Both gram positive.
What are the components of the endospores multilayer?
1. A cell membrane
2. A thick peptidoglycan mesh
3. Another cell membrane
4. A wall of keratin-like protein
5. An outer layer called the exosporium
What is a biofilm?
An extracellular polysaccharide network, similar to the capsule polysaccharides, that forms a mechanical scaffold around bacteria. It allows them to bind to prosthetic devices, like IV catheters, and protects them from attack by antibiotics and the immune system.
What is the main action of facultative intracellular organisms?
These bacteria inhibit phagosome-lysosome fusion.
Mention 8 important facultative intracellular organisms.
1. Listeria monocytogenes
2. Salmonella typhi
4. Francisella tularensis
Describe briefly what the exotoxins are.
Proteins released by both gram positive and gram negative bacteria.
What diseases can exotoxins cause?
What are the neurotoxins?
Exotoxins that act on the nerve or motor endplates to cause paralysis. Tetanus toxin and botulinum toxin are examples.
What are the enterotoxins?
Exotoxins that act on the GI tract to cause diarrhea.
What are the main actions of enterotoxins?
1. Inhibit NaCl resorption
2. Activate NaCl secretion
3. Kill intestinal epithelial cells
Common end result : the osmotic pull of fluid into the intestine, which causes diarrhea.
What are the two diseases caused by enterotoxins?
1. Infectious diarrhea
2. Food poisoning
Mention some bacteria that can cause infectious diarrhea.
1. Vibrio cholera
2. Escherichia coli
3. Campylobacter jejuni
4. Shigella dysenteriae
Mention some bacteria that cause food poisoning.
1. Bacillus cereus
2. Staphylococcus aureus
What are the pyrogenic exotoxins?
Stimulate the release of cytokines and can cause rash, fever, and toxic shock syndrome.
Mention 2 bacteria that can release pyrogenic exotoxins.
1. Staphylococcus aureus
2. Streptococcus pyogenes
What are the tissue invasive exotoxins?
Exotoxins that allow bacteria to destroy and tunnel through tissues.
These include enzymes that destroy DNA, collagen, fibrin, NAD, RBCs, and WBCs.
What are the exotoxin subunits in Bacillus anthracis, Clostridium botulinum, Clostridium tetani, Corynebacterium diphtheriae, and Vibrio cholera?
Composed of 2 polypeptide subunits bound together by disulfide bridges.
How are the two subunits of exotoxin called?
One is called B for binding of H for holding : binds to the target cell.
The other subunit called A for action or L for laser : enters the cell and exerts the toxic effect.
Why sometimes treating a patient who has a gram negative infection with antibiotics can worsen the things?
Because all the bacteria are lysed, releasing large quantities of endotoxin.
How is endotoxin different from exotoxin?
Endotoxin differs from exotoxin in that it is not a protein excreted from cells, but rather is a normal part of the outer membrane that sort of sheds off, especially during lysis.
What bacteria can cause septic shock?
Both gram positive and gram negative.
What is the different between bacteremia and sepsis?
Bacteremia : bacteria in the blood-stream.
Sepsis : bacteremia that causes a systemic response to the infection.