Shigella grows optimally at pH 4.5, but survives in a pH range of 2 to 5, permitting easy transit of these bacteria through the stomach.
Shigella strains produce at least two enterotoxins including a chromosome encoded Shigella enterotoxin 1 and a large plasmid associate Shigella enterotoxin 2.
Enterotoxins are bacterial products that act on the mucosal epithelium of the intestine, causing fluid secretion and profuse watery diarrhea. Normally they are heat stable and a low of molecular weight and water soluble.
Shigella enterotoxin 1 is chromosomally encoded, iron dependent toxin of 55 kDa that is primarily expressed by S. flexnery while encoded Shigella enterotoxin 2 is a plasmid-encoded protein of 63 kDa.
Shigellae caused bacillary dysentery. Ingested bacilli may infect villi of large intestine and multiply inside them.
Inflammatory reaction results in epithelial necrotic patch which later on become transverse superficial ulcers.
Transmission is by fecal-oral route, and stubborn reservoirs include day care centers, urban ghettos and rural village in developing countries.
Enterotoxin of Shigella
