Chapter 2: Cell Structures, Virulence Factors and Toxins Flashcards Preview

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Flashcards in Chapter 2: Cell Structures, Virulence Factors and Toxins Deck (26):

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
Francisella tularensis

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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



Bacteria in the bloodstream
Detected via cultures
Can occur silently and without symptoms
Can trigger immune system resulting in 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


Where is the most common site of infection?

lung, followed by abdomen and urinary tract


What are the 4 bacteria that produce exotoxins that increase levels of cAMP?

c = Cholera (Vibrio Cholera)
A = Anthrax (Bacillus anthracis)
M = Montezuma's revenge (toxigenic E. coli )
P = pertussis (Bordetella pertussis)