The ability of some Yersinia enterocolitica strains to invade HeLa cells

Many types of Yersinia enterocolitica have been isolated from animal, environmental, food, and human sources but their public health significance remains uncertain. Seventy two strains of Y. enterocolitica were tested for their abilities to invade HeLa cells. The typical clinical strains invade HeLa cells like the other species of invasive pathogens. This characteristic remains even in old stock cultures and can be temperature-sensitive like the motility characteristic. With the use of electron micrographs it was demonstrated that the bacteria were truly intracellular and not merely adhering to the HeLa cell membrane. The esculin-and salicin-positive typical clinical strains did not invade HeLa cells. None of 34 food and water isolates were invasive by this test. The negative Y. enterocolitica strains did not adhere to the cells and cause ambiguous results. The HeLa cell test is simple, inexpensive, rapid, and should prove useful marker for screening the Y. enterocolitica isolates.