Chapter 2: Cell Structures, Virulence Factors and Toxins Flashcards
What are Pili?
straight filaments arising from the bacterial cell wall
Adhesins: adherence factors
lose virulence if no pili
the flagellum is affixed to the bacteria by the _____ _____.
basal body
What does the basal body span the length of?
entire cell wall, binding to the inner and outer cell membrane in gram-neg bacteria and to the inner membrane in gram-positive
Capsules are usually composed of what?
simple sugar residues
Which bacteria is unique that its capsule is made up of amino acid residues?
Bacillus anthracis
How do capsules make bacteria more virulent ?
Mo and neutrophils are unable to phagocytize the encapsulated bacteria
What tests enable doctors to visualize capsules under the microscope to aid in identifying bacteria?
India ink stain: capsule appears as a transparent halo
Quellung reaction: abs used to bind to capsule
What bacteria form endospores?
Aerobic Bacillus and the anerobic Clostridum
What does the multi-layered protective coat of endospores consists of?
Cell membrane Thick peptidoglycan mesh Another cell membrane Wall of keratin-like protein Outer layer called exosporium
What is a biofilm?
extracellular polysaccharide network
allows it to bind to prosthetic devices
Protects from attack of Ab and immune system
What are the facultative intracellular organisms?
Listeria monocytogenes Salmonella typhi Yersinia Francisella tularensis Brucella Legionella Mycobacterium
Listen Sally Yer Friend Bruce Must Leave Now
What are exotoxins?
Proteins released by both Gram-positive and gram-negative bacteria
May cause disease
What are neurotoxins?
exotoxins that act on the nerves or motor endplates to cause paralysis
Tetanus toxin and botulinium toxin
What are enterotoxins?
Exotoxins that act on the GI tract causing diarrhea
Inhibit NaCl resorption, activate NaCl secretion, or kill intestinal epithelial cells
What is the difference between infectious diarrhea and food poisoning ?
INfectious diarrhea: bacteria colonize and bind to GI tract and continuously release enterotoxins locally until bacteria are killed
Food poisoning - bacteria grow in food and release enterotoxin, only enterotoxin enters GI causing vomiting and diarrhea for 24 hrs
What are pyrogenic exotoxins?
they stimulate the release of cytokines, cause rash, fever, toxic shock syndromes
Staphylococcus aureus, streptococcus pyogenes
What are tissue invasive exotoxins?
exotoxins that allow bacteria to destroy and tunnel through tissues
Destroy DNA, collagen, fibrin, NAD, RBC, and WBCs
Some exotoxins are composed of 2 polypeptide subunits bound together by disulfide bridges. What are the functions of B and A subunits?
B (also called H) binds to the cell
A (also called L) enter the cell and exert the toxic effects
What is Lipid A?
An endotoxin that is an outer piece of the membrane LPS of gram-negative bacteria
It is released on lysis of the cell
How do endotoxins differ from exotoxins?
Endotoxins are not proteins excreted from cells, but rather is a normal part of the outer membrane that sheds off during lysis
Bacteremia?
Bacteria in the bloodstream
Detected via cultures
Can occur silently and without symptoms
Can trigger immune system resulting in sepsis
Sepsis
Refers to bacteremia that causes a systemic immune response to the infection
Can be high or low temperature
Elevation of WBC
Fast HR or BR
Septic shock/ endotoxic shock
Sepsis that results in dangerous drops in blood pressure and organ dysfunction
Often endotoxin triggers the immune response; fungi and gram positive can also trigger
What are the endogenous mediators of sepsis?
TNF: also called cachectin –>weight loss
IL-1: from Mo and endothelial cells
