Chapter 2 Cell Structures, Virulence Factors and Toxins Flashcards
Where do flagellum attach to bacteria?
Basal body - spans the entire cell wall and spins around spinning the flagellum
What specialized flagellum do spirochetes have?
Periplasmic flagella - spirochetes are slender and tightly coiled - axial flagella come out of the ends of the cell wall but rather than protruding out of the outer membrane they run sideways along the spirochete under their unique outer membrane sheath
What is the function of pili?
Pili (aka fimbriae) are straight filaments that do not move but serve as adherence factors (adhesins)
List some examples of bacteria with pili
Neisseria gonorrhea - pili allow it to attach to cervical cells
E. coli and Campylobacter jejuni - attach to GI tract (diarrhea)
Bordella pertussis - attach to respiratory cells (whooping cough)
What are capsules made of? List one exception
Capsules are usually made of simple sugar residues that are secreted by bacteria
Bacillus anthraces is unique in that its capsule is made up of amino acid residues
What is the difference between (S) and (R) streptococcus colonies?
S = smooth colonies, have a capsule - rapid death when injected to mice
R - rough colonies, do not have a capsule - lost their virulence
Two tests for visualizing capsule
1) India ink stain - stain not taken up by capsule, capsule appears as a transparent halo around the cell (primarily used for Cryptococcus)
2) Quellung reaction - bacteria are mixed with antibodies that bind to the capsule, when they bind the capsule swells with water (can be visualized microscopically)
What is the process of antibodies binding to the capsule called? What is the next step?
Opsonization
Once the antibodies have bound to the bacterial capsule (opsonization) the macrophage or neutrophil can then bind to the Fc portion of the antibody and gobble up the bacteria
What bacterial genera produce endospores? What are endospores?
Bacillus and Clostridium
Endospores are metabolically dormant forms of bacteria that are resistant to heat (boiling), cold, drying and chemical agents
Which bacteria is known to attach to prosthetic devices like intravascular catheters and produce a biofilm that prevents attack by antibiotics and the immune system? How do you treat?
Staphylococcus epidermis
Treat by removing device
What are the facultative intracellular organisms?
Able to be phagocytosed by the hosts macrophages and neutrophils and survive within the WBCs unharmed (inhibit phagosome-lysosome fusion)
LISTen SALly YER FRiend BRUCE Must LEave NOw:
Listeria Monocytogenes Salmonella typhi Yersinia Francisella tularensis Brucella Legionella Mycobacteria Nocardia
What are the different types of exotoxins?
Neurotoxins: act on nerves or motor end plates to cause paralysis. Ex/ tetanus or botulinum toxins
Enterotoxins: act on GI tract to cause diarrhea (kill epithelial cells and push NaCl into the lumen - drags water). Can cause infectious diarrhea (E. Choli, cholera, Shigella dysenteriae, Campylobacter) or food poisoning (Staph. aureus, Bacillus cereus)
Pyrogenic toxins: stimulate the release of cytokines and cause rash, fever, and TSS. Ex/ Staph aureus and Strep pyogenes
Tissue invasive exotoxins: allow bacteria to destroy and tunnel through tissues
Exotoxin subunits B/H and A/L functions?
B (binding) and H (holding) bind to target cell
A (action) and L (laser) enter the cell and exert toxic effects
Define:
Bacteremia
Sepsis
Septic shock
Bacteremia: bacteria in the blood stream (can occur with brushing your teeth, or trigger the immune system leading to shock)
Sepsis: bacteremia that causes a systemic immune response to infection - high or low temperature, elevated WCC, fast HR or RR
Septic shock (endotoxic shock): dangerous drops in BP and organ dysfunction
Most famous endogenous mediator of sepsis? What does it do?
Tumor necrosis factor (TNF) aka cachectin
Triggers release of cytokine interleukin-1 from macrophages and endothelial cells -> triggers the release of other cytokines and PGs (first defends but ultimately turns against the body acting on bv and organs to produce vasodiation, hypotension, and organ system dysfunction)
