Bacterial adhesiveness and invasiveness in cell culture monolayer. 2. In vitro invasiveness of 45 strains belonging to the family Enterobacteriaceae.

The invasive potential of 45 presumptive enteropathogenic and non-enteropathogenic bacterial strains belonging to the family Enterobacteriaceae have been tested using the Serény test and HEp-2 cell monolayers examined by a combined light optical method. All the presumptive enteropathogenic strains of Shigella dysenteriae, S. boydii, S. flexneri, S. sonnei and Salmonella typhimurium showed in vitro invasiveness in the HEp-2 cell culture test. Fourteen presumptive non-enteropathogenic strains of Escherichia coli showed no invasiveness in either of the two test systems. Two strains of S. flexneri and all the 6 strains of S. typhimurium gave a negative result in the Serény test although they were invasive in HEp-2 cell cultures. Otherwise there were correlative results between the cell monolayer test and the Serény test. In the cell monolayer test the different species of enteropathogenic bacteria showed considerable variation in invasive potential.