Food Biochemistry and Food Processing

710

Table 31.2.

(Continued

)

Organism

Toxin Name

Toxin Type

Size of Toxin

Effect/Mode of Action of Toxin

E. coli

Shiga toxin 1

Verocytotoxin or

Subunit

Toxin exacerbates the severity of intestinal

O157:H7

(Stx1)

Shiga toxin

A—32

and systemic lesions in human hosts,

kDa,

tending to target the cortex of the kidney.

Subunit

It targets the intestinal villi cells and

B—7

glomerular endothelial cells because these

kDa

cells have Gb3 receptors for the toxins (Acheson and Keusch 1999, Melton-Celsa and O’Brien 1998).

Shiga toxin 2

Verocytotoxin or

Subunit

Toxin exacerbates the severity of intestinal

(Stx2)

Shiga toxin

A—32

and systemic lesions in human hosts,

kDa,

tending to target the cortex of the kidney.

Subunit

It targets the intestinal villi cells and

B—7

glomerular endothelial cells because these

kDa

cells have Gb3 receptors for the toxins. Stx2 is 1000-fold less toxic than Stx1 (Acheson and Keusch 1999, Melton-Celsa and O’Brien 1998).

Intimin

Adhesin

94–97 kDa

Intimin is an intestinal attachment and

effacement factor. The protein is important in intestinal colonization by the pathogen. The intimin receptor in the large intestine has not been elucidated (Kaper et al. 1998).

-hemolysin

Cytotoxin (pore

110 kDa

Toxin is Ca

2 

-dependent. It binds to an

forming)

unknown receptor in the host endothelial cells, polymorphonuclear leukocytes, monocytes, or T-lymphocytes and undergoes a conformational change to insert in the membrane, thus forming pores and causing osmotic lysis of the cells (Ludwig and Goebel 1999).