Shiga-Toxin-Producing Strains of O104:H4 and a Strain of O157:H7, Which Can Cause Human Hemolytic Uremic Syndrome, Differ in Biofilm Formation in the Presence of CO and in Their Ability to Grow in a Novel Cell Culture Medium.

One pathogen that commonly causes gastrointestinal illnesses from the consumption of contaminated food is O157:H7. In 2011 in Germany, however, there was a prominent outbreak of bloody diarrhea with a high incidence of hemolytic uremic syndrome (HUS) caused by an atypical, more virulent O104:H4 strain. To facilitate the identification of this lesser-known, atypical O104:H4 strain, we wanted to identify phenotypic differences between it and a strain of O157:H7 in different media and culture conditions. We found that O104:H4 strains produced considerably more biofilm than the strain of O157:H7 at 37 °C ( = 0.0470-0.0182) Biofilm production was significantly enhanced by the presence of 5% CO ( = 0.0348-0.0320). In our study on the innate immune response to the strains, we used HEK293 cells that express Toll-like receptors (TLRs) 2 or 4. We found that O104:H4 strains had the ability to grow in a novel HEK293 cell culture medium, while the O157:H7 strain could not. Thus, we uncovered previously unknown phenotypic properties of O104:H4 to further differentiate this pathogen from O157:H7.