Shiga toxin-producing Escherichia coli isolates from two 2006 outbreaks were compared to other O157:H7 isolates for virulence genotype, biofilm formation, and stress responses. Spinach-and lettuce-related-outbreak strains had similar pulsed-field gel electrophoresis patterns, and all carried both stx 2 and stx 2c variant genes. Cooperative biofilm formation involving an E. coli O157:H7 strain and a non-O157:H7 strain was also demonstrated.

The crystal structure of PD1 from the Haemophilus surface fibril was determined at a resolution of 3.3 Å, revealing a novel domain arrangement.