Intro to Specific Pathogens

Question 1

Serotype

Answer 1

Serotyping uses specific antisera that contains antibodies to specific bacterial antigens
-based on antibody recognition of antigens
O antigens: the polysaccharide component of LPS
H antigens: the flagellar antigen
K antigens: a polysaccharide capsule component

Question 2

O-antigen

Answer 2

made up of repeating oligosaccharide units, up to 20 different sugars can be found, and some unique to LPS
-O side chains easily recognized by antibodies of the host, and thus they vary o aid in immunevasion

Strains within a species can have different O-antigens

Question 3

Infectious Dose

Answer 3

Approximate number of microbes that, on average, are required to cause an infection
-person’s susceptibility to infection is affected by age, immune status, therapies, other infections, genetics, genetic diseases, or physical factors

Question 4

Virulence factors

Answer 4

enzymes involved in nutrient acquisition directly cause damage to the host
-examples: phospholipase, hemolysins, proteases

some of the enzymes are toxins or exotoxins because they are secreted from the cell

Question 5

Virulence determinant

Answer 5

factors required fro disease

Question 6

Endotoxin

Answer 6

gram-negative LPS in outer membrane contains endotoxin

Endotoxin causes fever and shock

Lipid A component of LPS is called endotoxin

Host innate immune system responds to low concentrations of endotoxin to enable rapid pathogen clearance

1. Macrophages activated by LPS secrete TNFalpha in tissue
2. Release of plasma proteins into tissue. Increased phagocyte and lymphocyte migration into tissue. Increased platelet adhesion to blood vessel wall.
3. Phagocytosis of bacteria.
4. Local blood vessel occlusion.
5. Plasma and cells drain to local lymph node.
6. Removal of infection.

Question 7

Endotoxic shock

Answer 7

Sufficient quantities of endotoxin induces endotoxic shock

• common and highly lethal (20-80% mortality) depending on pt. status and the microbe
• more than 20,000 people die from toxic shock each year in US
• Fever, inflammation, hypotension, DIC and bleeding, organ failure due to lack of oxygen

Many gram-negative pathogens cause local inflammation due to LPS, and if grow in blood(sepsis), endotoxin can induce endotoxic shock

Question 8

Strain

Answer 8

a population of organisms within a species that descends from a single organism

1. strains evolve within a species by mutation and/or by acquiring additional genes by horizontal gene transfer
2. surface components often vary among strains within a species to decrease detection or killing by a host or predator