Antigenic Structure/Toxins- Enterics

Question 1

Flagellar or “H” Antigens

Answer 1

From the German “hauch” or film. Weil and Felix used swarming strains of Proteus vulgaris for antigenic study and equated the swarm or film with motility. The flagellar antigens are protein in nature and heat labile.

Question 2

Capsular or “K” Antigens

Answer 2

Capsules are surface polysaccharides and also heat labile

Question 3

Somatic or “O” Antigens

Answer 3

“Somatic” means “body”. Somatic antigens are those associated with the “body” of the bacterial cell, as opposed to auxiliary structures such as flagella or capsules. Chemically they are the polysaccharide side chain of the lipopolysaccharide in the outer membrane. They are heat stable. (The “O” designation again came from Weil/Felix. “Ohne hauch” or “without film” was used to designate the non- swarming organisms.)

Question 4

Endotoxin

Answer 4

Release of the lipopolysaccharides (LPS) in the outer membrane of the cell wall of gram-negative bacteria can cause hypotension, shock, fever, intravascular coagulation, and death. The LPS’s are macromolecules composed of three main regions: lipid A, core polysaccharide, and “O” antigens. The Lipid A portion is the endotoxin component.

Question 5

Exotoxins

Answer 5

Exotoxins are toxic proteins liberated from a bacterial cell into the surrounding environment. They can be either heat-stable or heat-labile. Exotoxins can be produced by both gram-positive and gram-negative organisms.

Question 6

Enterotoxin

Answer 6

An exotoxin that acts on the intestinal tract. The enterotoxin can be produced in food and ingested or can be produced in the intestine. This toxin causes diarrhea or vomiting.