Chapter 2: Cell Structures, Virulence Factors and Toxins

Question 1

What are Pili?

Answer 1

straight filaments arising from the bacterial cell wall
Adhesins: adherence factors
lose virulence if no pili

Question 2

the flagellum is affixed to the bacteria by the _____ _____.

Answer 2

basal body

Question 3

What does the basal body span the length of?

Answer 3

entire cell wall, binding to the inner and outer cell membrane in gram-neg bacteria and to the inner membrane in gram-positive

Question 4

Capsules are usually composed of what?

Answer 4

simple sugar residues

Question 5

Which bacteria is unique that its capsule is made up of amino acid residues?

Answer 5

Bacillus anthracis

Question 6

How do capsules make bacteria more virulent ?

Answer 6

Mo and neutrophils are unable to phagocytize the encapsulated bacteria

Question 7

What tests enable doctors to visualize capsules under the microscope to aid in identifying bacteria?

Answer 7

India ink stain: capsule appears as a transparent halo

Quellung reaction: abs used to bind to capsule

Question 8

What bacteria form endospores?

Answer 8

Aerobic Bacillus and the anerobic Clostridum

Question 9

What does the multi-layered protective coat of endospores consists of?

Answer 9

Cell membrane
Thick peptidoglycan mesh
Another cell membrane
Wall of keratin-like protein
Outer layer called exosporium

Question 10

What is a biofilm?

Answer 10

extracellular polysaccharide network
allows it to bind to prosthetic devices
Protects from attack of Ab and immune system

Question 11

What are the facultative intracellular organisms?

Answer 11

Listeria monocytogenes
Salmonella typhi 
Yersinia
Francisella tularensis
Brucella
Legionella
Mycobacterium 

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Question 12

What are exotoxins?

Answer 12

Proteins released by both Gram-positive and gram-negative bacteria
May cause disease

Question 13

What are neurotoxins?

Answer 13

exotoxins that act on the nerves or motor endplates to cause paralysis
Tetanus toxin and botulinium toxin

Question 14

What are enterotoxins?

Answer 14

Exotoxins that act on the GI tract causing diarrhea

Inhibit NaCl resorption, activate NaCl secretion, or kill intestinal epithelial cells

Question 15

What is the difference between infectious diarrhea and food poisoning ?

Answer 15

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

Question 16

What are pyrogenic exotoxins?

Answer 16

they stimulate the release of cytokines, cause rash, fever, toxic shock syndromes
Staphylococcus aureus, streptococcus pyogenes

Question 17

What are tissue invasive exotoxins?

Answer 17

exotoxins that allow bacteria to destroy and tunnel through tissues
Destroy DNA, collagen, fibrin, NAD, RBC, and WBCs

Question 18

Some exotoxins are composed of 2 polypeptide subunits bound together by disulfide bridges. What are the functions of B and A subunits?

Answer 18

B (also called H) binds to the cell

A (also called L) enter the cell and exert the toxic effects

Question 19

What is Lipid A?

Answer 19

An endotoxin that is an outer piece of the membrane LPS of gram-negative bacteria

It is released on lysis of the cell

Question 20

How do endotoxins differ from exotoxins?

Answer 20

Endotoxins are not proteins excreted from cells, but rather is a normal part of the outer membrane that sheds off during lysis

Question 21

Bacteremia?

Answer 21

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

Question 22

Sepsis

Answer 22

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

Question 23

Septic shock/ endotoxic shock

Answer 23

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

Question 24

What are the endogenous mediators of sepsis?

Answer 24

TNF: also called cachectin –>weight loss

IL-1: from Mo and endothelial cells

Question 25

Where is the most common site of infection?

Answer 25

lung, followed by abdomen and urinary tract

Question 26

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

Answer 26

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