[Molecular biology in the pathogenesis of Shigella sp. and enteroinvasive Escherichia coli]. / Biología molecular en la patogenia de Shigella sp. y Escherichia coli enteroinvasiva.

Shigella sp and Escherichia coli (EIEC) are casual agents of bacillary dysentery, mainly in developing countries. Shigella and EIEC share biochemical, antigenic and genetic properties and probably they have the same mechanism of pathogenicity. Both species harbor a 120-140 megadalton plasmid, which is associated to the virulence and whose expression is regulated by chromosomal genes. Shigella sp and EIEC invade colonic epithelium and present virulence auxiliary factors, such as mucinases, superoxide dismutase and aerobactine production. On the other hand, cytotoxin production contributes to the illness' severity. The first step in invasion of the colonic mucosa is epithelium adherence, followed by endocytosis, lysis of the phagocytic vacuole, intracellular multiplication, intra-intercellular spread and killing of the host cell. Identification of these invasive organisms is carried out with the Sereny test, chicken embryo lethality and invasion to culture cells assays, DNA probe hibridization, polimerase chain reaction, ELISA, Congo red binding, and biochemical and serological tests.