[The discovery and study on invasive strain of Escherichia coli O121].

A strain of Enteroinvasive Escherichia coli was isolated from the stool with blood and mucus of a child suffering from acute diarrhea. The strain shows the following characteristics: rapid fermentation of glucose (with gas), no fermentation of lactose, beta-galactosidase reaction positive, growth in acetate media, lysine decarboxylase negative, non-motility causing keratoconjunctivitis in guinea pigs and invading into epithelial cells, with a plasmid of 140 Md, Serotype is O121:H- which is a new serotype of Enteroinvasive Escherichia coli.