Shigella is a genus of Gram-negative bacteria that is similar in behavior and habitat to Escherichia coli. The bacterium is named after its discoverer, Japanese scientist Kiyoshi Shiga. The bacteria were discovered over 100 years ago.

Some strains of the bacteria can produce toxins, including the so-called Shiga toxin, which is very similar to the destructive verotoxin of Escherichia coli O157:H7. Indeed, strain O157:H7 is now presumed to have arisen by virtue of a genetic recombination between strains of Shigella and Escherichia coli in the intestinal tract, which resulted in the acquisition of the verotoxin by Escherichia coli.

The similarity between Shigella and Escherichia coli extends to the structure of the bacteria and their utilization of certain compounds as nutrients. The similarity is so pronounced that Shigella has been regarded as a strain of Escherichia coli. However, this is now known not to be the case. Shigella...