Shigella dysenteriae 60R strain adheres to and invades tissue culture cells in the absence of virulence plasmid.

Evidence is presented that a high level Shiga toxin-producing strain Shigella dysenteriae 60R adheres to and invades the epithelial cell lines Hct8 and Henle 407. The invasive phenotype of S. dysenteriae 60R differs in four ways from the heretofore studied invasive Shigella phenotypes. First, S. dysenteriae 60R lacks the virulence plasmid characteristic of other invasive Shigella spp. and enteroinvasive Escherichia coli. Second, hybridization studies show that the known ipa genes are neither present in the chromosome nor in the small plasmid of 60R. Third, 60R adheres to and invades Hct8 and Henle 407 cells at 37 degrees C as well as at 30 degrees C. Fourth, the phenotype of adherence and invasion of 60R is remarkably stable, even during prolonged growth in laboratory media and storage.